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High-G Impact Detection - [Oyster3]

High-G event detection is supported by the Oyster3. 

When enabled, the Oyster3 accelerometer will detect High-G events exceeding the specified force and duration and log a record containing:

  • Log Reason 46 - 'High-G Event' 
  • Record Time
  • Last known GPS time and position (FID 0)
  • The Peak Force (FID 24)
  • The Average force (FID 24)
  • The Duration of the High-G event (FID 24)

Since the immediate record contains only the last known GPS position, the High-G Event Action can be configured to attempt a GPS fix after each High-G event. It can also be configured to attempt an upload with the result of the fix once, or to continue retrying the fix/upload until the Oyster3 succeeds, with increasing back-off timeouts in the event of failure.

Enabling High-G Impact Detection

  1. From within the OEM Server Interface, select your device
  2. Parameters → Edit System Parameters
  3. Add Advanced Parameters → Add the Accelerometer Settingsparameter Tab
    1. Set Alternate Function to High G
  4. Add Advanced Parameters → Add the High-G Detectiontab
    1. Select your High-G Event Option
      Typically Log+GPS+Upload Once is desired for an instant alert and position update when an event occurs

Selecting the High-G Threshold

Because the accelerometer is sensitive to gravity, it wakes up more easily when experiencing vertical forces. However, gravity is not considered when evaluating the criteria for logging. This filters out nuisance events from speed bumps, but might in extreme circumstances allow many High-G event wake-ups to go unnoticed, as they did not lead to a logged event. 

When using High-G detection in situations prone to repetitive vertical forces (for instance, on corrugated roads, or with continually vibrating machinery) be sure to set the force threshold high enough to avoid repetitive wake-ups, and the associated battery use.

The default threshold of 2Gs is suitable for regular vehicle tracking, where continuous vertical forces are not expected. To determine the minimum safe threshold in challenging environments:

  • Set the High-G Event Force threshold to its minimum value (1.5 G @ 10 ms)
  • Test the device in its intended application
  • If the detector doesn't go off, a threshold of at least 2.6 G is safe
  • If it does go off repeatedly, add at least 1.1 G to the reported peak force

High-G Event Detection Battery Life Implications

Because High-G detection requires the accelerometer to run at a higher speed than usual (100 Hz, versus the usual 12.5 Hz), it is disabled by default. This saves a small amount of battery.

The table below outlines the battery consumption from running the accelerometer at a higher speed when High-G events are enabled. 

High-G events may also trigger extra fixes and uploads, so this will also increase the battery consumption. Therefore you should factor this in when estimating the battery life on the Oyster3.

StateCurrent (uA)
% AA Lithium Battery/ Year
Accelerometer Off
0 uA0%
Accelerometer Low Power1.64 uA0.45%
Accelerometer High Power2.5 uA0.68%
High-G Low Power7.2 uA1.97%
High-G High Power14.9 uA4.08%

In addition to requiring additional battery power for the accelerometer, High-G events use battery when responding to each event. The device must wake up whenever it sees a large force, and verify that the force meets the criteria for logging. 

Setting Up Alerts

Alerts in 3rd Party Platforms

When a High-G event is detected, the Oyster3 will log a record containing:

  • Log Reason 46 - 'High-G Event' 
  • Record Time
  • Last known GPS time and position (FID 0)
  • The Peak Force (FID 24)
  • The Average force (FID 24)
  • The Duration of the High-G event (FID 24)

As such alerts can be set up to fire when Log Reason 46 is seen. 

Alerts and Reports in Telematics Guru

See how to set up an alert here

Ensure to give the alert a name and message in the General Tab; apply the alert to the relevant assets in the Assets Tab, and select who TG should send the alert to under Notifications.

In the Conditions tab, select 'Use Device Data Log Reason' and select High G Event from the list that's populated.

Timeline View

The Asset Timeline history view, will show a history of these alerts/events. 

High G Event Report

In Reports > All Reports, you can select the High G Event Report- Detail or Summary to view the occurrences of the High G Events with a variety of filters including Assets, Asset Types and Drivers with the date range as a parameter.

Peak-G, Average-G and Duration

In Telematics Guru, these values are reported in the following Analogue Fields:

Analogue 18:
Peak G-Force
Analogue 19:
Average G-Force
Analogue 20:
Duration of the event

They can be viewed in the device telemetry under Assets -> Telemetry.

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