Sensor Configuration

Owned by Ashley Mathews (Unlicensed)
Last updated: Apr 05, 2021 by Meagan Nicole Davis (Unlicensed)
3 min read

Creating a Sensor Event

  1. Create a new Event and set the Schedule Type to “Sensor Data“

    • Sensor Data can be scheduled to start at a specific time or any of the time offset (e.g., before sleep time)

  2. Add a Setting ('+') to the “Sensor Data“ Event, also called “Sensor Data”

    1. Device: “Android Wear”

    2. Choose a Sensor Type

      1. Pedometer

      2. HeartRate

      3. Accelerometer

    3. Repeat Count and Sensor Read Frequency (milliseconds)

      • These values are tied with the Schedule Type/Time to schedule the start of sensor data collection and set how long the delay between readings should be, and how many times the readings should repeat (a repeat of 0 means there will be 1 reading, a repeat of 1 means 2 readings, …).

      • “Repeat Count“ is the number of times per day that this Sensor Event will trigger. The time increment between Sensor Events = T / 1440 (There are 1440 minutes in a day), where T is the value of the “Repeat Count“ field. T = 480 means that the Sensor Event triggers every 3 minutes for the entire 24 hour day.

      • Frequency is the length of time between Sensor Events, in milliseconds (0.001 sec). Repeat Count is the number of times that the Sensor Data event will trigger during each 24-hour cycle, based on the Select Time which is the start of the first Sensor Event. It is the responsibility of the Study designer to ensure that (Frequency * Repeat Count) total is less than or equal to 1440 minutes, which is 1 calendar day.

      • It is recommended to not have multiple sensors firing at the same time. If you need heart rate and pedometer readings, they should be set at least a minute apart as readings (particularly HR) may take time to complete and requests may be dropped if a service is busy with another reading.

      • There is a max of number of “events”, subdivided by day, that can be scheduled. This is a platform limitation, and may vary by vendor but any study scheduling more than 200 events per day should take caution. There is a convention that will leverage “repeating” sensor events and will allow more data to be collected. However, no assessments can be associated with a repeating sensor event (ie, follow ups).

      1. If you wanted sensor readings every 10 minutes all day, you would set:

        1. Schedule Type = Specific Time

        2. Select Time = 12:01am

        3. Repeat Count = 143 ((60 mins * 24 hrs / 10) = 144 -1 for initial offset)

        4. Sensor Read Frequency = 600,000 (milliseconds)

  3. Post-Sensor Reading Logic (cannot be used for “repeating events, see above)

    1. If this formula evaluates to true, the Selected Assessments will trigger

      • Events will only trigger if it is during the participant’s waking hours.

    2. If left blank or if the formula evaluates to false, the event will passively collect sensor data.

    3. This formula is not limited to sensor specific formulas. The usual question based formulas work here as well if you need to reference other data.

Sensor Specific Formulas

  • GetStepsPerMinute(n)

    • Gets the average steps per minute over a given duration

    • Ex: GetStepsPerMinute(30) < 8 would get the average steps per minute from the last 30 minutes and trigger an assessment if that value is less than 8. (less than ~8.33 steps per minute is sedentary)

 

Using Sensor Data in a FollowUp Event

  • Additionally sensor readings can be generated through a “Follow Up” schedule type. For more information on how to setup FollowUp events, click here. Then start at the step 2 of the “Creating a Sensor Event” for setting up the Sensor Data setting.