The Basics

The Sensor Logger app is separated into five sections — Logger, Recordings, Studies, Stories and About. These sections are accessible via the tab bar at the bottom.

Logger

The Logger Screen allows you to start logging sensor data with a single tap. You can toggle which sensors you want to include in your recording. Tapping the green ‘Start Recording’ button begins a recording session. Tapping the grey gear icon on the Logger Screen allows you to configure sensors.

Recordings

On the Recordings Screen, you can view all your past recordings. By default, they are sorted from newest to oldest, but you can sort them differently by tapping the sort icon on the upper left. You can view, rename, export, or delete recordings by selecting them. You can also bulk delete and export by tapping the Select button on the upper right.

Studies

You can create or join Studies. Studies allow you to collect data from or contribute your data to other Sensor Logger users in a streamlined way. On this screen, you can see all the Studies you have joined as a participant, or that you own as an investigator.

Stories

Create and manage Story, the easiest way to build data-driven dashboards using Sensor Logger recordings. Here, you can see all your Stories and upload recordings, to be used visualised and analysed with any Story. These screens require internet access to work.

About

The About Screen provides information about the app, including its version number and the developer’s contact information. You can also subscribe to the Plus, Pro and Ultimate triers of the app, and access some of the paid features. Additionally, you can find links to additional resources to help you analyse your data, and the privacy policy of the app. If you have any questions or issues with the app, you can contact me directly from this page.

Starting a Recording

Begin a recording by navigating to the Logger Screen. Here you can see all the available and toggled sensors. Tapping the “Start Recording” button immediately starts a recording.

Supported Sensors

The list of available sensors varies depending on the hardware available on your phone. If you don’t see a specific sensor, it is likely not available on your device. To refresh this list, you need to quit and restart the app.

• Device Acceleration (Accelerometer; Raw & Calibrated), G-Force
• Gravity Vector (Accelerometer)
• Device Rotation Rate (Gyroscope)
• Device Orientation (Gyroscope; Raw & Calibrated)
• Magnetic Field (Magnetometer; Raw & Calibrated)
• Compass
• Barometric Altitude (Barometer), Atmospheric Pressure
• GPS: Altitude, Speed, Heading, Latitude, Longitude
• Audio (Microphone)
• Loudness (Microphone), Sound Meter
• Camera Images (Front & Back, Foreground)
• Camera Video (Front & Back, Foreground)
• Pedometer
• Heart Rate (Requires Apple Watch App)
• Wrist Motion (Requires Apple Watch App)
• Watch Location (Requires Apple Watch App)
• Watch Barometer (Requires Apple Watch App)
• Light Sensor (Android Only)
• Annotations (Timestamp and Text)
• Device Battery Level and State
• Device Screen Brightness Level
• Nearby Bluetooth Beacons (All Advertised Data)
• Nearby WiFi Networks (Android Only)
• Battery Temperature (Android Only)
• Headphone Motion (Requires AirPods)
• Network

Some sensors may have various quirks and limitations which are also often platform specific. Always check the in-app description for each sensor by tapping the “eye” icon next to the sensor.

Toggling Sensors

To turn sensors on or off, tap the toggle next to them. When you first toggle a sensor, Sensor Logger may prompt you to request for the relevant permissions. It is important that you follow the stated instructions to ensure the proper functioning of Sensor Logger. This may include location, microphone, or health data access. You can toggle all sensors on or off using the “Toggle All” button on the top right.

Sensors with Additional Permissions

Some sensors require additional permissions. If they are not granted yet, there will be a yellow warning icon next to it. Toggling the sensor should prompt you with the relevant permission request prompt. If that is not the case, tapping the yellow warning icon will direct you to your phone’s settings page for Sensor Logger.

Previewing Sensors & Live Readings

Tap on the eye icon next to each sensor to preview the values. Where relevant, you will see a plot showing the last 100 readings from the sensor. You can also find a short description of the sensor, along with sampling and unit information.

Live Readings Head-up Display

To view the live, raw values for any sensor, tap the “eye” icon and then the “enlarge” icon on the top right.

Starting a Recording from a Watch

If you have a paired Apple Watch, you can install the companion watch app to log heart rate and wrist motion data. You can also start and stop a recording remotely from your watch. As long as the phone and the watch are in range, you will see a button to start and end a recording session.

Problematic Recording State

If the “Start Recording” button is orange, this means Sensor Logger may not be fully functional when you start a recording. This can be due to:

• You have toggled any watch-related sensors on, but your paired watch is not reachable at the moment.
• You have reached the maximum number of allowed recordings on the free tier (10 maximum). You can delete some existing recordings to work around this limit. Otherwise, consider upgrading to one of the paid versions of Sensor Logger.
• Location permission is not set to “Always” — Sensor Logger relies on this permission to enable background recording for any sensor, not just location. If you do not grant this permission, you can still use Sensor Logger, but background recording may be compromised.
• You have toggled the Camera sensor, but you have not granted Sensor Logger camera-related permissions.
• Low battery.

You can start a recording even when the button is orange, but your recording may be incomplete or the behaviour of Sensor Logger may be unexpected.

Ending a Recording

Tap the End Recording button to end a recording. This is available one second after the start of the recording — the minimum recording duration is one second. You can customise the behaviour of Sensor Logger when you end a recording using the Workflow concept. You can also automate the ending of a recording via the Rule Engine.

During a Recording

Going into the Background

All sensors, with the exception of Camera, offer some form of background recording — meaning times when the app is not on-screen in the foreground or when the device is locked. To ensure the sensor values are being collected in the background reliably, you should:

• Most importantly, grant Sensor Logger background location access — usually termed “Always Allow”. you have to do this explicitly being going to the settings app of your phone. This location permission gives Sensor Logger enough privilege in the background to run. This also applies even if you are not interested in location data. By granting this location permission, Sensor Logger can stay in the background more reliably.
• Sometimes, low power mode may interfere Sensor Logger when in the background.
• On iOS, certain Focus modes may affect Sensor Logger when in the background.
• For Apple Watch users, you have to enable the Heart Rate sensor in order to collect measurements in the background (i.e when your arm is down and the Watch screen is not active).
• The Camera sensor does not support background mode due to operating system limitations. You have to keep the viewfinder on-screen at all times to reliably capture images.
• Bluetooth sensors may have limitations in the background. It may work, depending on the specific sensor, configuration, and operating system. You’re encouraged to experiment and test before you perform a real recording.

To guarantee Sensor Logger to work reliably all the time, please use the Keep Awake option, which can be enabled in the settings. This option will keep your phone screen on during recorder in, and thus guaranteeing Sensor Logger to be in the foreground all the time. To conserve battery, use Keep Awake along with the dim option to keep the phone screen brightness to a minimum level

Preventing Sensor Logger From Going into the Background

For whatever reason, if you wish not to have Sensor Logger going into the background — either because the sensor you want does not support background (Camera, Bluetooth etc.), you do not want to grant Sensor Logger “Always Allow” location permission or you just want the highest level of guarantee of the app not getting killed by the operating system, you have two options:

• Enable Keep Awake to prevent the screen from getting turned off.
• Enable Proximity Lock (New in Version 1.3), which uses the proximity sensor to turn the screen off whilst the phone is in the pocket — but the otherwise behaves as though it is in the foreground.

App Crashes or Out of Battery

If the app crashes during a recording session, Sensor Logger will attempt to recover the recording. This should work most of the time. However, you may notice a discontinuity in the recording timeline. This also applies if you run out of battery and your phone dies.

Adding Annotations or Bookmark

As of version 1.8, you may now add timestamped annotation during a recording session. You can find this feature on the Logger screen when there is an active recording session in progress. Tapping the icon with the pencil icon, you can type any text comment associated with the timestamp. Note that the timestamp is the moment you tap the pencil icon, not the moment you commit the text message. Tap and hold to control the duration of the message. If you leave the text field empty, only the time will be logged. Due to the way CSV works, comma characters “,” are removed from the text field.

Bluetooth Beacon Support

Unlock unlimited potential as Sensor Logger supports logging messages broadcasted by Bluetooth beacons.

Logging Specific Bluetooth Sensors

Sensor Logger supports logging advertised messages from nearby Bluetooth devices. On the Logger screen, scroll to the Bluetooth section and tap “Refresh”. Sensor Logger will then scan for nearby devices for a period of time, which are then listed in the order of their signal strengths. Both the scanning duration and minimum signal strength threshold (RSSI threshold) can be configured. You can then toggle them on or off to be included or excluded from a recording session like any other on-device sensor. Note that toggling more than 2 Bluetooth sensors at a time would require a paid subscription.

To learn more about how to parse and interpret the logged Bluetooth sensors, please check https://github.com/tszheichoi/awesome-sensor-logger/blob/main/README.md#recording-bluetooth-le-sensors.

Logging All Bluetooth Sensors

Sometimes, you might want to select the Bluetooth sensor in your post-analysis, or perhaps the sensor you want to log is out of range when you initially start logging. To support these use cases, you can also log all nearby Bluetooth sensors by toggling the Bluetooth sensor at the very top. Note that using this toggle would require a paid subscription. Further, due to operating system limitations, the screen must be on and Sensor Logger must be in the foreground for this to work reliably.

Companion Apple Watch App

If you have an Apple watch with the free companion watch app installed, you can log additional sensors on your watch on the iOS version of Sensor Logger:

• Heart rate
• Wrist motion (rotational and acceleration measurements)
• Location
• Barometer

To install the companion watch app, open the Watch app on your phone after you install Sensor Logger on your phone. Then you should see an option to also install it on your watch.

When you first launch the watch app, you'll be asked to grant access to heart rate measurements. It's crucial to allow this access — without this permission granted, you won't receive measurements reliably from your watch.

The companion watch app can be run in two modes:

• Phone & Watch Mode
  • To make synchronised measurements across phone and watch.
  • You must have your phone nearby throughout the recording session.
  • Recording is immediately available on your phone after the session.
  • Works with other Sensor Logger features on your phone, such as Studies, Streaming and Rule Engines.
• Watch Only Mode
  • To make standalone recordings on the watch.
  • No phone-based sensor
  • You don’t need your phone nearby to start.
  • Data is transferred to the phone afterwards. Recording takes time to transfer to the phone.
  • Does not work with other Sensor Logger features, such as Studies, Streaming and Rule Engines.
  • Cannot take annotations.

You can swipe left and right to switch between the two modes.

Using Phone & Watch Mode, Start on the Phone

Below the the watch sensors on the phone’s Logger screen is the current status of the watch app connectivity. If it says ‘Watch Connected’, the companion app is up and running and ready to send heart rate measurements. If it says ‘Watch Disconnected‘, the watch app is currently not in the foreground on your watch. You may still start the recording session, but measurements will not start until you launch the watch app. Once the watch app is launched, it may go into the background, and the measurements will continue. If the watch disconnects during a recording (e.g. the watch is taken off the wrist or runs out of battery), the recording session will continue on the phone, but the measurements from the watch will stop.

Using Phone & Watch Mode, Start on the Watch

On the watch app, you may start and stop recording sessions, even if you are not recording any watch-based sensor. In this case, the watch can act as a remote. If the button says “App Disconnected”, this is likely that your watch is unable to communicate with the phone. Please ensure the iOS app is still running. You may start a recording session from your watch even if the phone app is not in the foreground, as long as it is still running in the background.

Using Watch Only Mode

Toggle the relevant sensors you want to log and tap Start Recording on the watch. The phone does not need to be nearby for this. Once the session ends, the data will transfer to the phone in the background. This can take a while, depending on the connection status. You can see the number of currently pending files for transfer.

Notes on Heart Rate Measurements

Please note that the heart rate’s sampling rate is unpredictable and controlled by the watch’s operating system. Typically, the measurement comes in once every few seconds.

Configuring Sensors

Sensor Logger offers extensive customisation to help you record exactly what you need. Some of the configurations below do require a paid subscription. Tap the gear icon on the Logger screen next to the Start Recording button to reveal the configuration screen (Hint: tap and hold the same button to see the screen on a view-only mode)

Confirm Before Ending

To prevent the accidental ending of a recording, you can opt to have a confirmation dialogue when you tap “End Recording”.

Smart Name

Automatically name recording based on the current location. This is only available when the Location sensor is enabled and there is an Internet connection. When available use the first GPS coordinate and perform geocoding. Note that this may not always be accurate, you may need to adjust the recording name afterward. The geocoding is performed by the operating system and does not go through Sensor Logger’s servers. As always, your data and location is always private.

Keep Awake

Keep the screen on and prevent Sensor Logger BLE Beta from going into the background during a recording session. This is useful if you want to record sensors that may not reliably work in the background, such as certain Bluetooth, sensors, and cameras. Use the “On & Dim” option to also dim the screen, which may help conserve battery life.

Workflows

There are two workflows you can have with Sensor Logger.

• In the classic workflow, upon ending a recording session, data is saved in the background for management and exporting later. This is useful for bulk data collection.
• In the integrated workflow, upon ending a recording session, you will be prompted to rename and export the data in just a few taps.

Your data is always saved regardless of the mode. Recordings ended on the companion watch app always follow the classic workflow.

Additional Data

By default, Sensor Logger logs calibrated and processed values by the operating system. Toggling the “Uncalibrated Values” means raw values from accelerometer, gyroscope and magnetometer are also logged. This is useful for performing lower level post-processing or custom sensor fusion. Calibrated data is always logged.

On Android only, by default, only fused location is logged. If enabled, additional measurements from GPS only and from the network only are available in separate files.

Name Caching

Sensor Logger can remember how you name your recordings based on the Location sensor, if enabled. Next time, if you start a recording within approximately 100m, then it will default This is only available when you use the integrated recording Workflow. The cached names stay on your device, and you can reset the naming cache by resetting the configuration.

Camera Configuration

In this section, you can select whether you are using the front or rear facing cameras to capture images. You can also enable the flash here, and choose the image quality when capturing images when the camera sensor is enabled. Higher quality images will take up more space. When set to Lowest, image processing skipped entirely to maximise frame rate.

For the Camera Mode option, you can select either Images or Video. If Images is selected, Sensor Logger will capture individual images at set interval as separate files. If Video is selected, Sensor Logger will capture a continuous video as a single file. In this case, the sampling frequency option is ignored entirely. The video file will include audio, If and only if the microphone sensor is also enabled.

Microphone Configuration

Choose the quality of the audio recording. Lossless is the highest quality, but will take up the most space. Loudness will only log the loudness of the audio, and not the audio itself.

Location Configuration

By default, when the Location sensor is enabled, Sensor Logger logs with the highest possible precision. However, if you’re not interested in the precise location you may consider cloaking the coordinates to enhance privacy. Sensor Logger around coordinates to the nearest 0.001° and 0.1°, which correspond approximately 100 meter and 1 km respectively. If “Drop” is selected, no locational coordinates will be logged at all — in this case, only GPS values, such as the altitude, speed, heading etc. are saved.

Bluetooth Configuration

You can adjust how long Sensor Logger scan, nearby Bluetooth devices for. You can also tune the minimum signal strength threshold.

Sampling Frequencies

You can adjust the sampling frequency for groups of related sensors via the gear icon on the Logger screen. Note that the sampling frequency for each sensor depends on the combination of your phone’s operating system and hardware constraints. Sensor Logger can only suggest an approximate desired sampling frequency but has no direct control of the actual sampling. It is recommended that you experiment with the settings and examine the output to determine the actual sampling frequency. Your sampling frequency settings are saved locally on your phone, so you do not need to reconfigure them every time.

Note that battery optimisation may interfere with the sampling frequency unpredictably. If you are experiencing issues, consider checking whether your phone is in any low-power mode.

Standardisation

Android and iOS may report values in different units and coordinate systems, making cross-platform analysis difficult. Toggle “Standardise Units & Frame”, and Sensor Logger will automatically harmonise the conventions across platform, so you can focus on the data analysis and worry less about units and definitions. This standardisation is off by default. For more information about what this standardisation do, and what sensors and affected, please see https://github.com/tszheichoi/awesome-sensor-logger/blob/main/CROSSPLATFORM.md

Recordings made with standardisation on will be marked in the Metadata.csv file, so you can easily distinguish them.

Sensor Sections

You can re-order how the sensor sections appear on your logger screen so that you can pin more commonly used sensors on the top for easier access.

HTTP Push

As of version 1.10, Sensor Logger supports pushing live data via HTTP. This can be enabled by tapping the gear icon on the Logger page. All enabled sensors during a recording will be streamed every set period to the specified URL. The set period is every second by default, for Plus and Pro users, this is configurable in the Sensor Settings page. To display the streamed data, you will need to set up a web server on another computer.

As of version 1.27, you can optionally skip writing data to disk when HTTP Push is enabled. This is useful if you want to conserve on-device disk space and have your data pipeline rely entirely on streamed data.

Setting Up a HTTP Push Web Server

To learn more about HTTP Data Push and how to leverage this functionality fully (along with sample code), see https://github.com/tszheichoi/awesome-sensor-logger/blob/main/README.md#live-data-streaming. Be aware of internet data usage if you’re on cellular. Certain sensors may push a lot of data fairly rapidly.

If you setup your server to return error code 499, you can signify to Sensor Logger that something has gone wrong on your server. Sensor Logger will display an alert, along with the response text.

MQTT Publish

As of version 1.30, Sensor Logger supports pushing live data via MQTT. Both HTTP Push and MQTT have the same schema, configurable batching period and supported sensors. The only difference is the protocol. HTTP has a simpler setup and is more widely supported. On the other hand, MQTT is more lightweight and popular for IoT applications. Sensor Logger also supports simultaneous HTTP pushing and MQTT publishing. Note that:

• Sensor Logger publishes with a quality of service level 0 (at most once).
• Sensor Logger only supports websockets. Typically websockets are on port 8000 (no TLS) or 8884 (TLS). TCP connections are not supported, which are typically on port 1883 (no TLS) or 8883 (TLS).

Setting Up a MQTT Broker

For more information about configuring publishing and setting up a MQTT broker, see https://github.com/tszheichoi/awesome-sensor-logger/blob/main/PUSHING.md#mqtt-publishing.

Dynamic MQTT Topics

Topics may include ${deviceId} and ${sessionId}, which are dynamically injected during publishing.

Export, Share & Restore Configuration

All settings on the settings page and the state of the currently toggled sensors can be exported using a generated code. This code can then be used to restore the settings on the same device or another device. You can even share the code with others to ensure they have the same settings when they collect data on your behalf. Simply forward them the code or ask them to scan the QR code on their phones. The code and QR code update every time you adjust a setting on the page.

Note that if you have any paid features, it will also be part of the exported configuration. However, in order to restore and apply it, the target phone needs to have a subscription as well. Otherwise, the configuration will only be partially restored.

Restore Default Configuration

To restore all configurations back to their default, you can tap “Restore All Settings to Defaults” at the bottom of the sensor configuration page. Note that this action cannot be undone, and will override all your existing configuration, including any rules you might have composed.

Rule Engine

Sensor Logger comes with an intelligent Rule Engine where you can write custom rules to automate your data collection intelligently based on sensors, location, and time.

Enabling the Rule Engine

To enable the rule engine, go to settings and “Rule Engine”. Toggle Rule Engine on at the top of the screen. When turned on, you will also see a note on the Logger screen above the Start Recording button.

Composing Rules

Intuitive rules editing interface allows you to compose complex data-capturing logic without needing to write a single line of code. Go to the Rule Engine section of the settings to begin. Tap the Add Rule button to add a new rule block.

If Conditions

Conditions are under the “If” section. All conditions must be simultaneously met before the rule is triggered. These conditions may include:

• Any sensor measurement (except Bluetooth sensors)
  • If conditions in the same rule block involve multiple sensors, be mindful of their sampling frequencies. The Rule Engine caches values for up to 30 seconds for this purpose.
  • Make sure all the relevant sensors are also toggled on in the Logger screen.
• Time of day. Support local or UTC time.
• Day of the week. Supports local or UTC time.
• Duration since the beginning of the recording.
• Geofencing, with the center coordinate and a radius.

You can combine multiple conditions in your rule. Conditions are evaluated from top to bottom in order — once any condition is evaluated to be false, the rest of the conditions in the same rule block will be skipped.

Then Actions

Actions are under the “Then” section. These are the actions that are taken when all the conditions are met. Actions are taken from top to bottom in order. Actions that can be triggered include:

• Adjusting sensor sampling.
• Adding tag. Duplicated tags will be ignored.
• Adding a timestamped annotation.
• Ending recording: Once ended, you cannot resume the recording. Further, none of the then actions after this will be triggered.
• Pausing: All sensors are still active, but no new data will be written.
• Resuming recording: To be used in conjunction with Pausing.
• Send notification: Select from one of the preset notification messages. You may be asked to allow notifications when you add this condition for the first time. Note that there is a global notification rate limit of one per minute for anything triggered via the rule engine — this is enforced even across recording sessions.

Delete & Duplicate Rules

You can delete or duplicate any rule block by tapping the vertical ellipsis icon at the top right of each rule block.

Rearrange Rules

Rule blocks are evaluated from top to bottom in order. Long press on the rule block title and drag to reorder them.

Notes on Rule Evaluation

It is important to understand how the Rule Engine executes your rules.

• Rules are only evaluated during a recording session. You must tap “Start Recording” first before any rule takes effect.
• Rules are evaluated:
  • Whenever there is a new measurement from any sensor.
  • Once every minute.
• To ensure reliable evaluation in the background, you must grant Sensor Logger “always” permission.
• If there are conflicting actions, the last one will take precedence.
• Remove unused rules to improve performance.
• Is compatible with HTTP Push, and any action taken will be respected — such as any changes in sampling frequency, pausing, or resuming.

Help with Rules and examples

On the Rules Editor page, tap “Help & Tips” to access additional information and tips for how to write rules. If you need example rules and inspiration, tap “Examples & Rules Gallery”. Here, you will see a list of example rule blocks, along with suggested use cases. Tap “Copy Template” to make a copy of the template, which you can modify further to suit your needs.

Troubleshooting Rules

Every time a rule is triggered, a log is created in the recording for traceability. You can view these logs:

• Live, by tapping the console button next to the End Recording button.
• Afterward, by navigating to the recording and tapping “Rules”.

Sharing Rules

Rules are compatible with the Studies feature, meaning you can prescribe rules on other Sensor Logger users’ devices when they join your study. Rules can also be exported, shared, and restored using the settings sharing feature. See the “Export, Share & Restore Configuration” section for more information.

Viewing Recordings

You can view all recordings you have made in the Recordings Screen. In this list view, you can see the name, recording start time (in local time), recording duration and any associated tags. Tapping each recording will bring you to the recording details screen.

Sorting Recordings

By default, the list is sorted by recording time, with the newest recording at the top. You can sort the list differently by tapping the sort arrows at the upper left-hand corner. You can sort by:

• Newest or oldest
• Longest or shortest in duration
• By recording name, alphabetically.

Filtering Recordings by Tags

You can assign tags to recordings. They are useful for conveniently organising your recordings. The tags for each recording, if any, are shown alongside the recordings in the list view. To filter by a specific tag, you can tap any of the tags along the top of the screen. If you have many tags, you may need to scroll horizontally the view them all. Once tapped, the list is filtered to only recordings with that tag assigned. Selecting further tags narrows your search. If no recordings match the selected set of tags, you will see no recoding. To deselect any tag, tap it again. To deselect all tags, tap “Show All”.

Batch Delete & Export

To export or delete multiple recordings, tap the “Select” button at the upper right. You can tap the recordings of your choice to select them. Once you are happy with your selection, you can tap “Delete” or “Export” at the bottom of the screen.

Limitations

The free version of Sensor Logger supports only up to 10 stored recordings. To store more recordings on your device, you can consider upgrading. To stay within the limit, you may need to export and delete some existing recordings.

Inspecting a Recording

Tap any recording on the Recordings screen to inspect it. Here you can see all the associated files for that recording. Tapping each allows you to preview each associated sensor.

Inspecting Metadata

Each recording contains at least one Metadata file. This file contains essential information such as device property, time zone, and sampling frequency. Additional Metadata files may exist:

• Bluetooth Metadata, if one or more Bluetooth sensors are enabled. This will contain the device name device UUID.
• Study Metadata, if the recording is made as part of a study with a questionnaire (See Study). This will include all the questions and any answers you may have provided.

Renaming a Recording

To rename a recording, tap the “Rename” button on the details screen.

Assign Tags to a Recording

To assign or un-assign tags to recordings, tap the “Tags” button on the details screen. This will bring you to the tags editor. To assign existing tags or unassign currently selected tags, simply tap the tags on this screen. Note that once a tag has been disassociated from all recordings, it will be deleted. To create a new tag, simply type it into the text box at the top and tap “Add Tag”.

Note that if a recording is made as part of a Study, it will acquire a special tag, corresponding to the name of the Study. If that Study uses Sensor Logger Cloud, it will additionally acquire a tag indicating whether the recording has already been uploaded or not.

Deleting a Recording

To delete a recording, tap the “Delete” button on the details screen. You will be asked to confirm this action. Once deleted, your data will not be recoverable.

View Measurements

To view measurements, tap the name of the sensor of interest on the details screen. You will then see an interactive plot of the data. If you have a long recording with many data points, you may only see the beginning parts of the recording. To view more, tap the bar at the top. This will lower the resolution of the plots, but will allow you to view longer durations.

If you tap on Microphone or Camera, if applicable, then you will be able to playback the audio or view the images, respectively.

Interacting with Plots

Here are some tips to help you with interacting with plots on Sensor Logger.

• Tap and drag to zoom into a specific part of the plot;
• Tap and drag the axes to pan in respective directions;
• Tap and drag the edges of the axes to zoom;
• Double-tap anywhere on the plot to reset the view;
• Tap on a legend item to hide its trace;
• Double-tap on a legend item to hide all other traces

Exporting Plots

You can export any visualisation by tapping the “Share Current Plot” button under any graph.

Exporting Recording

This can be done in the details screen for each of the recordings. Tap the “Export” button and you will be brought to to export screen. Here you can change the format of the export and the name of the exported file. Some file formats require a paid subscription:

• CSV in Zip File (Recommended) – All data will be exported in csv format, with the exception of audio files and images, if applicable. All data will then be zipped into a single CSV file for convenient exporting. This is the only way to export all data associated with a recording reliable.
• Combined CSV — By default, sensors write to separate CSV files. Use this option to combine them into a single CSV file. This involves resampling the measurements, and downsampling or upsampling when needed, depending on the sampling frequency of the sensors. This results in a single CSV file that is easier to share, analyse and plot. Tap on the options to configure the resampling strategies:
  • Resampling: Resampling is the process of grouping data together. Grouping is needed because different sensors may have different sampling rates. For example, if one sensor samples at 1Hz and another samples at 10Hz, you can resample to every 1 second, in which case the latter sensor needs to be upsampled; or you can resample to every 10 seconds, in which case the former sensor needs to be downsampled. The resampled range is closed and labelled on the left: E.g. at a 1 second resampling, the label 2 seconds implies a time range of 2 to 3, inclusive of 2 but exclusive of 3.
  • Numeric Downsampling: Numeric downsampling is the process of combining multiple numeric values into a single value. Maximum and Minimum are useful if you are interested in extrema. Average is useful if you want to capture the general trend, but it can be skewed by outliers, which median is more robust against.
  • Non-Numeric Downsampling: Non-Numeric downsampling is the process of combining multiple non-numeric values into a single value, such as booleans and texts. Mode is useful if you are interested in the most common value. First and Last are useful if you are interested in the first or last value in the group, even if they are nulls.
  • Upsampling: Upsampling is the process of filling in missing values. Null is useful if you want to be explicit about missing values. Forward fill is useful if you want to fill in missing values with the last known value.
• JSON – Package all data into a single JSON file for easy parsing. Measurements from multiple sensors are interlaced. Note that this does not include any audio or images, if applicable.
• Excel Sheets – Package all data into a single Excel file. Measurements from multiple sensors are organised into separate sheets – each up to 10K rows long. Note that this does not include any audio or images, if applicable.
• KML – Export only location information, if relevant, as a single KML file. All other sensors or data are excluded.
• SQLite — Export the recording as a single SQLite database, organised into tables with appropriate typing.

Whatever your selected file format is, you can change the name of the exported files using one of the templates. The templates include permutations of:

• Recording name
• Readable Local date and time
• Readable UTC date and time
• Epoch UTC date and time
• Unique device ID
• Platform name (e.g. iOS, Android)
• Aggregation strategy (only available when exporting file format is Combined CSV)

Note that local times are determined using the time zone at the time of export, not a the time of recording. Whatever you have selected will be remembered so you won’t have to reselect the next time you export your recordings.

Exporting to File System

You can export the recording onto the phone's file system for use in other apps. The process differs slightly on iOS and Android. On iOS, you can tap “Save to Files” to save into the local file system. On Android, you can tap the “Save file” share target (with the Sensor Logger logo) to save into the local file system.

Exporting Individual Sensor Data

Alternatively, you may export data from individual sensors within a recording as a standalone .csv file. To do this, simply tap the sensor of interest on the details screen. You will see an interactive plot along with an export button (‘arrow icon’) on the upper right-hand corner. Tap the arrow to export.

The time column of the exported CSV is the Unix epoch time in nanoseconds. For conversion, please see, for example, https://www.epochconverter.com/

Clearing Export Cache

When you export a recording, the zip file is cached locally so that the app does not need to re-zip the recording the next time you tap the share icon. This means that the zip file, along with the raw recordings, is taking up storage space on your phone. At the bottom of the Recordings screen is a button that will clear all cached zip files. This will not delete any raw data, and the app will always re-zip the recordings the next time your tap the export button.

Organising Recordings with Tags

You can add tags to your recordings. Tap the Tags icon on the recordings detail page. This will bring you the Tags editor. You can add new tags using the text box at the top. You can use anything thing as tags, including Emojis. If you already have some tags set, you can see them listed at the bottom of that same page. Tap any to assign, and tap again to unassign. Once a tag has been disassociated from all recordings, it will be removed.

Tags can be used to filter recordings. All the available tags are shown as tappable pill icons towards the top of the Recordings Screen. Tapping any, or combinations, will apply the corresponding filters. Tap again to unselect any filtering. Tap Show All to remove any tag-based filtering on the recordings.

Studies

Studies allow you to collect data from or contribute data to other Sensor Logger users in a streamlined way.

As an Investigator

As an investigator, studies allow you to:

• Define exactly how you want your data to be collected.
• Define exactly how you want your data to be packaged.
• Define exactly how you want your data to be transferred. for other Sensor Logger users.
• If you have access to any paid features (e.g. advanced sensor configuration and file formats), your participants will temporarily inherit these when they collect data for you at no additional cost to your or the participants.

As a Participant

As a participant, studies allow you to:

• Contribute data to a study effortlessly.
• Understand why and how your data is collected and intended to be used.
• Leave, join or switch study any time.
• Collect data in exactly the way the study investigator has prescribed, meaning you have less to worry about.
• Own your recordings and data.

Joining a Study

You can join a study in one of two ways:

1. You have been given a QR code. You can just scan the QR code with your phone’s camera app. You will then see a page detailing the study. Once you have read about the study, then you can join with the “Join Study” button. You can also scan the QR code with the app’s built in camera: Navigate to the Studies tab, then tap “Join / Create” on the top right corner. Then tap “Find a Study” and “By QR Code”. You may need to permit Sensor Logger to access your camera for this to work.
2. You have been given an 8-digit code. Navigate to the Studies tab, then tap “Join / Create” on the top right corner. Then tap “Find a Study”. Enter the code then tap “View Study”. Once you have read about the study, then you can join with the “Join Study” button.

Additionally, please note that:

• You can join participate in up to 40 studies at a time.
• You must have an internet connection when you join a study.

Viewing All Joined Studies

On the Studies screen, make sure you have selected “As Participant” along the top. You will then see a list of currently participating study.

Activating & Deactivating a Study

On the Studies screen, make sure you have selected “As Participant” along the top. To the right of each recording is a toggle switch. Toggle any to activate a study. You can have at most one activated study at a time.

Alternatively, tap any participating study on the list to view more details. On the Study Details screen, you will see a large “Activate” (green) or “Pause” (red) button. Tap it to activate or deactivate a study.

Viewing Study Details

In the Studies tab, tap any participating study on the list to view more details. Here, you will see the name of the study, its investigator name and the study identifier (Study ID), which you can tap to copy.

You will also see two action buttons depending on whether the study is currently activated. The left button allows you to activate or deactivate a study. The right button allows you to leave a study (see below). Below, in the Details section, you will find:

• Description: The purpose of the study, as described by the study investigator.
• Point of Contact: Where you should email should you have any questions about the study and how your data is used. You can tap the address to compose a new email.
• Enabled Sensors: The enabled sensors for this study. If the your device does not support all, it will be a subset of what is being specified here.
• File Format: How your recordings will be packaged up when being sent to the study investigator.
• Sharing Method: Whether your study investigator has opted for Manual or Sensor Logger Cloud as delivery methods. If former, the study investigator will have provided instructions on how to upload the data. If latter, you can upload to Sensor Logger cloud with a single tap of a button. Once uploaded, the study investigator, and only him/her, will be able to see and retrieve your data from the cloud.
• Privacy Statement: How your data will be used and protected, as described by the study investigator.
• Created at: Date of study creation.
• Ending at: The date which the study will end. After this date, you will no longer be able to activate and contribute to this study.
• Study Duration: the duration of the study in number of days.

Note that:

• Tap the info icon next to each detail section to access additional tips.
• Information displayed on this page are provided by the study investigators, and is not endorsed by or screened by Sensor Logger in any way.

Recording for a Study

Activate a study, and navigate to the Logger screen. When a Study is activated, you will see a helpful hint bar along the top of the Logger screen to make it explicit that you are currently recording for a study. Tapping the bar brings you back to the study details. The exact sensor configuration, as prescribed by the investigator, is used to ensure data collection consistency. All your configurations on the logger screen and the settings screen are locked until you deactivate or leave a study.

You can record as usual. You own all recordings you’ve made for a study. You can view, export and manage them like any normal recording.

When you end a recording for a study, you will be immediately prompted with a dialogue to rename the recording. Rename it to something that will be useful to the study investigator. You may also not give the recording a name if you wish not to do so. Tapping “Continue”, if:

• the study has opted for a Manual delivery method, the upload instructions, as provided by the study investigator, will be shown. Sensor Logger prepares the data for export in the background and subsequently presents you with a share sheet, which you can act on based on the instructions. You can also share and follow the instructions later on in the Recordings screen.
• the study has opted for Sensor Logger Cloud, then you will be able to upload your recording. If you tap “Upload Now”, Sensor Logger will handle the rest – packaging, uploading and allowing the study investigator to access your data later on. During the upload, please do not close Sensor Logger. Once uploaded, your recording will acquire a “Uploaded” tag, indicating it has been successfully uploaded. In the same dialogue as “Upload Now”, You can also choose to upload later if you have a weak connection, have no internet connection, or are on mobile data. In this case, your study will acquire a “To Upload” tag, reminding that you need to upload the recording later. To upload later on, simply visit the Recordings screen, tap the recoding with the “To Upload” tag, and tap upload.

Browsing Recordings Made for a Study

When working with Sensor Logger, there are two ways to view recordings made for a study.

The first way is to go to the Recordings screen and filter by study name. This method is useful if you want to view all recordings made for a specific study. All recordings made for a study will have a tag named after the study, which makes it easy to filter and find them.

The second way to view recordings made for a study is by going to the Studies screen. Here, you can select the study you're interested in and open the Recordings tab. This method is useful if you want to see all the recordings made for a specific study in one place.

For studies that use Sensor Logger cloud, recordings that have not been uploaded yet will have a cloud icon next to them, reminding you to upload them at a later time. This is a useful feature as it ensures that all recordings are uploaded and available for analysis.

Leaving a Study

Once you have finished participating in a study, you can explicitly leave it. This will free up the study participant quota for others to join. All recordings you have made will still be available locally, provided you have not also deleted the recordings separately and manually.

Expired Studies

All studies have end dates. Once ended, if you:

• have already joined the study, then you will no longer be able to activate it or upload recordings to the study. However, your recordings recorded for this study will always be there locally, regardless of whether the study has expired or not. If you have not uploaded them to Sensor Logger Cloud, you will not be able to do so. Contact the study investigator for further instructions.
• have not already joined, then you will not be able to join the study – even though you can still see the study details.

Expired studies have a yellow warning icon next to them on the Studies screen to indicate their expiry.

Deleted Studies

The study investigator may choose to delete a study, if you:

• have already joined the study, then you will no longer be able to activate it or upload recordings to the study. However, your recordings recorded for this study will always be there locally, regardless of whether the study has expired or not.
• have not already joined, then you will not be able to join the study.

Creating a Study

To create a new study, navigate to the Studies screen. Then tap “Create / Join” at the upper right-hand corner. Then tap “Create a Study”. On this page, you can customise everything about a study.

• Basic Information: This includes the study name, investigator name, contact email, study description, and privacy statement. Please be as specific as possible with these fields to help your participants understand the nature of the study. You can also tap the “shuffle” icon next to each field to have Sensor Logger randomly generate a suggestion to get you started.
• Sensor Selection: Toggle the sensors on or off for this study based on the available sensors on the participant's device. If the participant's device does not support all the listed sensors, a subset of the specified sensors will be used. If the participant's device supports more sensors than the ones listed here, those additional sensors will be turned off.
• Configuration: Configure the sensors and how you want the data to be packaged up (file format and naming pattern). Once set, the participant’s configuration will be locked to these values for as long as they participate in the study. If you have access to paid features, all your participants will also temporarily inherit these for free for the duration of the study.
• Data Delivery: Select how you want your participants to send their recordings back to you. See the Data Delivery section below. If you have selected Sensor Logger Cloud, you will see an overview of the remaining cloud storage that you have. If you have selected Manual, then you will have to enter the upload instructions below. Again, tap the “shuffle” icon for some random inspiration to get you started.
• Questionnaire: Optionally collect additional information from the participants to support your study. This is only available to users with subscriptions. Your subscription tier determines how many question you can create per Study.
  • There are two types of questions:
    • Join Study questions are presented when a user joins a study initially. This is useful for collecting information about the participant — e.g. name, study-specific identifier, contact details etc. Note that once the participant has joined a study, the answers to these questions will not longer be editable. if the same participant leaves and rejoins the study, the latter answers will override the former ones.
    • Recording End questions are presented every time a recording ends whilst the study is active. This is useful for collecting information that will change across multiple recordings by the same participant — e.g. for a study tracking car journeys, you may want to collect license plate number or the colour of the car; for a medical study, you may want to ask the participant to note down their mood or activity level. These questions can be changed after the fact in the Recordings screen, up until the recording is uploaded to Sensor Logger Cloud if you opt to use it for your study.
    • Both Join Study questions and Recording End questions are packaged up as a JSON, to be included in every export of recordings.
    • If you use Sensor Logger Cloud as the recording delivery mechanism, all questions and answers are also viewable in a table format so you can quickly triage and download recordings based on the participant’s answers.
  • In addition, each question must have:
    • A field name.
    • A short description to explain to the users what you are collecting and why. Please be specific.
    • Optional (default) or not. When optional, the participants may opt to skip answering those questions.
    • A type, which can be one of the followings.
      • Text, where the participants can enter free-form text.
      • Number, where the participants can enter numbers in a keypad.
      • Email, where the participants can enter text using an email keyboard. Note that this does not validate or guarantee valid email.
      • Select, where you provide a list of options where the participants may choose from. There must at least be 2, and up to 20, options per question.
      • Sign, where the participant can doodle a signature.
  • Note that, on creation, the study investigator is automatically enrolled as a participant too. Because of this, the investigator will use up a one quota of the study size. You can leave the study to free up the spot if you wish to. Further, during this automatic initial join, the investigator will not be presented the joining questionnaire. As a result, you will not have the opportunity to answer those questions, even though they may be mark as non-optional.
  • The number of questions you can create for questionnaire varies based on your subscription tier.
    • 1 questionnaire in the Free tier
    • 3 questions allowed in the Plus and Pro tiers
    • Up to 100 questions allowed in the Ultimate tier
    • Need more? Contact me.
• Study Identifier: By default, a random identifier is assigned to a newly created study. You can customise this if you wish to. You can pick any 6 to 8 digit alphanumeric string. This is only available to users with the Ultimate subscription.
• Study Participants: Select how big your study should be in terms of the number of participants.
  • Small, up to 3 participants — Free for all Sensor Logger users
  • Medium, up to 10 participants — Plus or higher tier
  • Large, up to 100 participants — Pro or higher tier
  • Extra Large, up to 1K participants — Ultimate or higher tier
  • Even larger? Contact me.
• Study Duration: Select how long your study should run for. This can be extended even after the study creation. Once a study ends, participants will no longer be able to activate or contribute to a study.

Note that:

• With the exception of the end date, all information on the create study screen cannot be changed after the study has been created.
• Anyone who has the QR code / study join code will be able to see the study details and join the study.
• Requires an internet connection to create a study.
• There are some limits on how many studies you can actively own at a time. If you hit this limit, consider deleting some existing studies or upgrading to a higher subscription tier.
  • Up to 2 simultaneous studies — Free for all Sensor Logger users
  • Up to 5 simultaneous studies — Plus tier
  • Up to 10 simultaneous studies — Pro tier
  • Up to 20 simultaneous studies — Ultimate tier
  • Want more? Contact me.
• When you create a study, you are automatically added as a participant. This is done to allow you, as the creator, to actively participate and contribute data. It's important to note that this automatic inclusion as a participant consumes one participant quota. If you wish to free up this slot, you can choose to leave the study. Rest assured, you will still retain ownership of the study and have access to it as an investigator. Please be aware that if a study includes questionnaires labeled as "Join Study" type, the process of automatic inclusion upon study creation bypasses the presentation of these questionnaires. Consequently, you won't have the opportunity to respond to them at that time.

Data Delivery

There are two ways Study participants can deliver their data back to the study investigator. Between the two, Sensor Logger Cloud is recommended as it is the most streamlined and requires the least amount of setup from the investigator.

Via Sensor Logger Cloud (Recommended, Most Streamlined)

The first method is through Sensor Logger Cloud, Sensor Logger’s managed service for data security and integrated recordings delivery. With a single tap at the end of a recording, participants can upload the recording there and then. Sensor Logger will handle the rest.

• Upload can happen immediately after the recording session, or afterwards in the Recordings screen.
• Only the study investigator can see and download the uploaded recording with an automatically generated password.
• Study participants cannot see or download their uploaded recording — they will only get acknowledgment that the recording has been successfully submitted.
• Submitted recordings count towards a storage quota for the study owner (not participants). Once this is full, no further uploads are allowed. See the Sensor Logger Cloud section below for more information.

Via Manual

The second method is through manual delivery. At the end of each recording, the participants will be given an instruction, provided by the study investigator, on how to upload their data. Use this method if:

• As per your research institution's policy, participants’ data cannot go through a third party.
• You already have a process for collecting data from the research participants.

Inviting Participants to a Study

To invite participants to join a study, you can follow these steps:

1. Go to the Studies screen in the Sensor Logger app.
2. Tap on the study that you want to invite participants to.
3. Once you're on the study details page, navigate to the Invite tab.
4. Here, you will see three ways to share the study with participants: using a link, using a QR code or an eight-digit study code.

The recommended way of sharing a study is via the link. When a prospective participant does not have Sensor Logger installed, it will redirect to the correct page where they can download the app. If they already have Sensor Logger installed, it will link them directly to the Study page where they can join with a single tap.

If you choose to share the study using a QR code, participants can simply scan the code with their phone's camera app. This will take them to a page that provides more details about the study. Once they have read through the information and are ready to join, they can hit the "Join Study" button.

Alternatively, if you choose to share the study using an eight-digit study code, participants will need to do the following:

1. Navigate to the Studies tab in the app.
2. Tap on "Join / Create" in the top right corner.
3. Tap on "Find a Study".
4. Enter the study code that you provided.
5. Tap on "View Study".
6. Once they have read through the information and are ready to join, they can hit the "Join Study" button.

Please note that participants will need to have an internet connection in order to join the study using either method. It's also important to keep in mind that each study can have up to a certain number of participants, depending on the tier of your Sensor Logger subscription. Be sure to check your subscription details to ensure that you don't exceed your participant limit.

Tracking the Progress of a Study

To manage an existing study, navigate to the Studies screen. Ensure you are viewing the list as an investigator by tapping the “As Investigator” section at the top. Select the study you want to manage, then tap “Stats”. You can see:

• How many days remain in this study
• How many participants have joined
• If Sensor Logger Cloud is used
  • How many recordings have been uploaded
  • How much storage is left

Extending a Study

All studies have an end date, which can be extended indefinitely — up to 30 days into the future at any given point in time. When viewing a study as an investigator, you can tap the pencil icon next to the “Ending at”.

Editing a Study

After a study has been created, you can update certain properties of the study. You will need to be connected to the internet in order to do so:

• Description
• Point of Contact
• Investigator Name
• Study Size
• Privacy Statement

Deleting a Study

To delete a study, go to the Studies screen. Make sure you are viewing the list as an investigator by tapping the "As Investigator" section at the top. Select the study you want to delete, then tap "Delete" in the upper right-hand corner. Keep in mind that this action is irreversible, and participants will be removed from the study once you delete it.

Sensor Logger Cloud for Studies

Sensor Logger cloud is an optional service run by Sensor Logger, used along side Studies. Sensor Logger streamlines the data transfer process between study participants and investigators. When a study is created, the investigator can opt to use Sensor Logger Cloud as the data delivery mechanism. With a single tap after a recording session, the participants will be able to safely and securely copy a version of their recording to the cloud.

Each Sensor Logger user has an allocated amount of cloud storage. Recordings uploaded to the cloud count against the investigator’s storage quota (not the participants). The limits are:

• 100MB for everyone (Free)
• 1GB for Sensor Logger Plus users
• 10GB for Sensor Logger Pro users
• 100GB for Sensor Logger Ultimate users

Additionally, each uploaded recording has a maximum size limit of 5GB each. This is limit applies to everyone. If you require more, please reach out. Storage quota is shared across all studies owned by an investigator, not by study. If you have reached your storage limit:

• Participants can no longer upload to the study, but can still make recordings for a study.
• Any uploaded recordings remain safe and available.

To free up some storage, consider:

• Upgrade to a higher Sensor Logger tier.
• Download recordings from an existing study and delete the study.
• Contact me.

If you downgrade to a lower tier, but is using more storage then the tier you are downgrading to, your data will be safe and is not deleted, but your participants will no longer be able to upload to your study until you upgrade again or remove some existing recordings. To check your current storage limit and usage, navigate to the Studies screen. Ensure you have “As Investigator” selected at the top. Then you should see your Sensor Logger Cloud usage details along the bottom of the screen.

Downloading Uploaded Recordings

Via Web Interface (Recommended)

Go to the Studies screen and make sure you are viewing the list as an investigator by tapping the "As Investigator" section at the top. Select the study you want to delete, then tap "data”. Tap the shown link or copy it to a computer. You will then be asked to enter a secret code. Generate the code by tapping “Generate New Code” and then copy it. Enter the code on the website to see a list of all uploaded recordings. You can either download all at once or tap each recording to download them one by one.

Note that:

• The generated code is the password and should be kept as a secret.
• If you regenerate the code, all past codes will be invalidated.
• The Download All button may not behave well depending on the browser. This is due to limitations of the browser multi-download mechanisms. The Download All button has been tested on Chrome. If you have large amounts of file to download, consider using the API with a download script — see below.
• The recordings will be available for the duration of the study, and will appear as soon as recordings are uploaded. Once a study has ended or deleted, it will remain available for download for an additional 90 days.
• The Upload ID column refers to a unique identifier assigned to each uploading device. This is to help you more easily identify groups of recordings from the same device. Note that if the same person uploads from multiple devices, then the Upload ID may differ. If the participant changes the Google Play or Apple ID, the Upload ID may also change.

Via API (For Large Scale Automation)

You can list, download and delete uploaded recordings via an API. For documentation, please refer to https://github.com/tszheichoi/awesome-sensor-logger/blob/main/STUDY_API.md.

Stories

Stories are dashboard-style, data-driven notebooks designed specifically for your Sensor Logger recordings. With Stories, you can:

• Visualise and explore your data with advanced time series and geo-spatial tools. Enhance data storytelling with contextual information like text, images, links, weather, reverse-geocodes and metadata.
• Perform data analysis with SQL, or pick from one of the no-code options, like time alignment and frequency analysis.
• Effortless sharing as Stories are hosted on the web.

Stories are backed by Sensor Logger Cloud, where you can upload recordings in a single tap.

Creating a Story

Stories are created inside the Sensor Logger app. To get started, navigate to the Stories tab and tap Create at the upper right hand corner. From here, you can create a new Story in one of three ways:

• From a template, which is recommended if you’re getting started with a Story. You can select one of many pre-made templates for various applications and use cases.
• From scratch, if you know what you are doing and want to create a blank Story.
• Duplicate from an existing Story. You can duplicate a Story you own or a Story that has been shared with you. To do this, you will need a code to an existing Story.

Regardless of which route you pick, you’ll end up in the Story creation screen. Here, you can title your Story, add a description and give it an appropriate emoji. Don’t worry, all these can be modified later. Then tap Create Story to create the story. All created Stories will appear under the Stories tab.

There are no limitations to how many Stories you can create, so create and experiment with as many as you wish to!

Browsing Story Templates

Templates help you get started with Stories with ease. You can use them to try out and understand how Stories can be built, and what are the generally supported capabilities.

To view the Story template gallery, navigate to the Stories tab and tap Create at the upper right hand corner. Then tap View Gallery. When viewing the gallery template, you can see from the tags what sensors, visualisation features and analyses those templates are designed to demonstrate. Tap on each template to view more details and example screenshots.

Every template can be previewed interactively with real data. Tap the link to copy and paste into any web browser to preview the template. During preview, you can edit and modify the template Story any way you want — you can even attach your own recording — but you cannot save it.

Once you’re happen with the template, tap “Use Template”. This will bring you to the Story creation screen. Modify the name, description and emoji if you wish to, or leave them as-is based on the template. Then tap “Create Story”.

Viewing a Story

All created Stories that you own will appear under the Stories tab. Internet connection is required to load this. Tap on any Story to view it’s details. Under the Access tab, you will see one of two ways to view the Story:

• Via a link, which you can tap to copy. This link should work on any web browser, but Stories are more optimised to be viewed in large computer screens.
• Via a QR code.

Editing a Story

Stories are edited on the web. Use the same link you use to view the Story to edit that Story. Make sure you click the Save button once you are done.

Locking & Unlocking a Story

Anyone with the Story link, by default, can view and edit it. If you intend to share the Story with others as view-only, make sure you lock it before sharing. Once locked, a story is still editable and interactive

Managing a Story

Tap on any Story to view it’s details. Here you can delete, refresh, duplicate or lock your Story.

Sharing a Story

The link you use to access and edit Story yourself is the same link you use to share your Story. If you do not want others to edit your Story, make sure you lock it before distributing the link.

If you want to revoke all previous access and invalidate the existing link, you can do so by generating a new link. Tap the Generate New Link button at the bottom of the Access tab.

Uploading Recordings for Stories

To use a recording in a Story, it must first be uploaded to Sensor Logger Cloud, a safe and secure store for all your recordings. Sensor Logger Cloud is free to use and all users get 100mb of storage for free. Upgrade to increase the storage limit.

To upload a recording, go to the Stories screen and tap on the Recordings tab. Here, you’ll see a list of all uploaded recordings, with both the recording time and upload time. To upload a new recording, tap Upload at the upper right. Here, you’ll see a list of local recordings. Tap on any to start the upload. You can tap on multiple to bulk upload (up to 3 uploads in parallel). Once a recording is uploaded, it cannot be re-uploaded again.

These uploads to Sensor Logger cloud includes all your raw data, tags and any Study questionnaires. However, they exclude any video, image or audio. Please also note the following restrictions and limits for recordings uploaded to Sensor Logger Cloud:

• There is a 1GB limit for recordings uploaded to Sensor Logger Cloud. If you require more, please reach out.
• Recordings backed-up to Sensor Logger Cloud are guaranteed to be retained as long as they have been accessed in the past 12 months. A recording is accessed as long as it has been viewed in any Story at least once. After the 12 month period, we retain the right to delete any recording that has not been accessed.

Use a Recording in Stories

Once uploaded, your recording can then be used in a Story. To do so, tap on your uploaded recording to find its 9-digit secret code. One the Story, under any Source, enter the corresponding code.

Sharing Uploaded Recordings

The secret code for any uploaded recording can be shared with others. With that code, anyone can use it in their Stories and download the associated recording. To revoke access once shared, simply tap Generate New Code. This will generate a new secret code and invalidate any previous ones.

Managing Uploaded Recordings

You can rename and edit all your uploaded recordings by tapping on the relevant recording in the Recordings tab under Stories.

Customising the Look & Feel

To customise the app according to your preferences, you may opt to change the theme colour and app icon. This feature is accessible through the About Screen, where you can modify the app's appearance to suit your taste by picking one of the many colour presets. Some colours are free, whilst others requires you to be subscribed to any paid tier. Changing the app icon is only available for users with a paid subscription — any subscription tier will do.

Awesome Sensor Logger

Sensor Logger is often a tool as part of a wider data analysis and research workflow / pipeline. I have prepared some simple resources to help you make the most out of your data. This also includes basic code snippets that you can adapt for parsing and cleaning Sensor Logger outputs. See https://github.com/tszheichoi/awesome-sensor-logger. If you’ve any scripts or documentation that you think other Sensor Logger users may find useful, do make a PR on the GitHub. Additional, you will also find:

• Units Reference
• Coordinates Reference
• Schema for Streaming

Paid Tiers

Sensor Logger is full-featured, free of charge, and is not supported by ads. However, should you want to support the development of the app, please consider subscribing to one of the paid tiers.

Plus

• For personal, academic and research use.
• Advanced sensor configuration.
• Additional timestamp formats.
• More than 10 recordings stored.
• More theme colours to choose from.
• Change the app icon.
• More exporting formats.
  • .xls, where each sensor is a new sheet.
  • .bluetoothkml, for location data only.
  • .sqlite, where each sensor is a new table.
• Support the development of Sensor Logger.
• Unlimited number of simultaneously enabled Bluetooth sensors.
• Unlimited number of rules.
• Up to 1GB of Sensor Logger Cloud storage.
• Create studies with up to 10 participants.
• MQTT support.
• Advanced Study configuration:
  • Questionnaires with 1 question.

Pro

• Everything in Plus.
• Paid tier for using Sensor Logger commercially including email support.
• Up to 10GB of Sensor Logger Cloud storage.
• Create studies with up to 100 participants.
• Advanced Study configuration:
  • Questionnaires with up to 3 questions.
  • Delete select recordings without the need to delete the whole study.
  • Setup notifications for participants (if they opt-in)
    • Reminder to start a recording (up to 4, daily and/or weekly reminders, at specific time of day)
    • Recording upload reminder (up to 1 reminder 6 hours later, if the participant did not upload their recording)

Ultimate

• Everything in Plus and Pro.
• Up to 100GB of Sensor Logger Cloud storage.
• Create studies with up to 1000 participants.
• Advanced Study configuration:
  • Custom Study ID.
  • Questionnaires with up to 100 questions.
  • Delete select recordings without the need to delete the whole study. This can be done either via the web portal or programmatically via API.

To Subscribe

To view pricing information and subscribe, visit the About screen in the app, then tap “Subscribe”. Pricing and availability may vary depending on location.

Once subscribed, you can use the subscription on all devices that are signed into your App Store account at no additional cost. Note, however, that subscriptions are not sharable or transferable across Android and iOS.

To Unsubscribe

To unsubscribe, please refer to the corresponding app stores — subscriptions are managed via the Google Play Store / Apple App Store, not directly by Sensor Logger.

For iOS: Open Settings. Tap your name. Tap subscriptions. Find the subscription and cancel it.

For Android: Open the Google Play app, tap the profile, tap Payments and Subscriptions, find the subscription and cancel it.

If you encounter any issues, do reach out via email.

One-Off & Bulk Purchases

If you prefer non-recurring, one-off purchases, or require bulk purchase of license, you can do purchase paid licenses online (not in the app). Each license purchased this way lasts one year from date of purchase and can be used on one device.

Visit https://sensor.tszheichoi.com/purchase to view pricing and configure how many licenses you want to purchase. All payments are handled securely via Stripe, and invoices are available. Once purchased, you will receive a set of activation links via email, each activating one device.

Contact Me

If you have any questions, comments, or concerns, please email me. I typically respond within 48 hours during most times of the year. Alternatively, you can also visit our FAQ page for answers to commonly asked questions.

Other Known Issues

• Please note that the accuracy of timestamps relies on accurate system timestamps. Please make sure your phone’s time is accurate to ensure physically correct timestamps. If your phone changes time zone mid-recording, it may also lead to unpredictable behaviour.
• Recordings may be incomplete if the app crashes or if the phone is turned off mid-recording. Upon the next start-up, the app will attempt to salvage any partial recording. This is not guaranteed to work for all sensors. For example, audio recordings cannot be salvaged.
• In iOS 15, if you are experiencing watch disconnection issues, try disabling Focus Mode, particularly any Focus Mode that is triggered automatically when the devices go into fitness mode.

And Finally

If you found this app helpful, please consider leaving a rating or review on the app store. Your feedback helps us improve the app and make it more useful for others. Thank you for using Sensor Logger!

FAQ

Some Sensors Report Zeros on iOS

If any of your sensors report zeros during a recording session, try the following (https://www.lifewire.com/how-to-calibrate-an-iphone-4172146):

1. Open Settings.
2. Turn on the Location Services toggle switch, then scroll down and tap System Services.
3. Turn on the Compass Calibration and Motion Calibration & Distance toggle switches.

My Watch Keeps Disconnecting

If you keep experiencing watch disconnection issues during a recording session, please first make sure the heart rate sensor is enabled (see above), even though you may not be interested in the heart rate data. Second, make sure the app is granted location and health permissions on both the phone and the watch. Finally, the following order of operation usually gives a solid connection.

1. Start Sensor Logger on the iPhone;
2. Start a workout session on the Apple Watch, with the workout app;
3. Start Sensor Logger on the Apple Watch;
4. Press ‘Start Recording’ in the Sensor Logger app on your iPhone.

These steps should get the connection into a stable state. For further tips and reference on how to improve the watch app’s reliability, please see https://www.tszheichoi.com/sensor-logger-watch-reliability

I Don’t See My Sensors

If you don’t see a specific sensor on the Logger Screen, it is likely not available on your device. This list is refreshed when the app starts up from scratch — so try quitting and restarting the app if you want the app to double-check. This is useful when you have a newly paired Apple Watch with Sensor Logger installed.

How Do I Ensure Apple Watch Connection Reliability?

You can employ the following strategies to ensure that measurements made with Sensor Logger on the Apple Watch gets transmitted and saved in Sensor Logger on the iPhone reliably:

• Always enable Heart Rate sensor, even if you’re not interested in its measurements. By enabling Heart Rate, Sensor Loggers get additional privileges to ensure reliable background operation on the watch.
• Make sure you grant Sensor Logger the necessary health permissions to access your heart rate measurements. You need to check this on both the Settings app on your watch and your phone.
• Ensure the watch is within range of the phone throughout the recording session.

For more information, please see https://www.tszheichoi.com/sensor-logger-watch-reliability.

Is Sensor Logger free to use?

Sensor Logger is full-featured for free. You have access to all sensors, and can make as many number of recordings as you wish. All recording management features are also free. There are certain advanced configurations, colour and icon customisation, and file export formats that require a paid subscription. Another limitation of the free version is that you can only have 10 stored recordings at a time — but you can always export and delete existing recordings to make more.

How many studies can I join?

You can join up to 30 studies at a time. Leave existing studies to join more.

I Cannot Load the Subscription Pricing

Sometimes, pricing information on the Subscribe page may not load properly in certain countries. If you experience issues, please first try connecting to a different network (e.g. cellular, and check if you’ve any VPN enabled) and try again. If the issue persists, do reach out via email along with your customer ID — you can find this at the bottom of the Subscribe screen, which you can tap to copy.

What Projection Coordinate System Does Sensor Logger Use?

Sensor Logger uses the location API from the operating system. On both Android and iOS, it is WGS84. See https://developer.apple.com/documentation/corelocation/cllocation and https://developer.android.com/reference/android/location/Location for more information.

Is My Bluetooth Device Supported

Sensor Logger supports Bluetooth devices that broadcast their data without explicit connection. These are known as BLE or Bluetooth beacons. See this article for how this is different to devices that require pairing: https://www.allaboutcircuits.com/technical-articles/bluetooth-low-energy-transfer-modes-a-comparison. Sensor Logger supports both legacy and extended advertisement.

Does My AirPods Support Headphone Motion Logging

Only some AirPod models support headphone motion tracking on iOS. The easiest way to identify this is to check whether your model supports Spatial Audio. You can find more information on Apple’s documentation: https://support.apple.com/en-us/102469. Further you should ensure that your AirPod is paired properly with the phone you are running Sensor Logger on.