REXGEN 2 IMU GNSSManual
REXGEN 2 IMU GNSS: recording motion and position
Fit the GNSS antenna to REXGEN 2 IMU GNSS. Then record position, acceleration and rotation on the same timeline as your CAN, LIN and input data. This guide applies to REXGEN 2 IMU GNSS only.
Fit the GNSS antenna
REXGEN 2 IMU GNSS has an internal GNSS receiver and needs an external active antenna with a 3 V supply. The antenna in the box comes on a 5 m cable and screws onto the female SMA socket next to the micro USB port.
- Connect the antenna before you power the logger. Screw the SMA plug on firmly by hand.
- Route the cable. Lead the 5 m cable to where the antenna has a view of the sky, and secure it so it cannot pull on the socket.
- Keep it connected. Never run the logger with a loose antenna or without one. If the antenna is loose or missing, the logger loses GNSS data.
Record GNSS position
The receiver uses GPS, QZSS, GLONASS, BeiDou and Galileo signals and records position at up to 18 Hz.
| Item | Value |
|---|---|
| Update rate | Up to 18 Hz |
| Receiver | u-blox, 72-channel |
| Position accuracy | 2.0 m CEP |
| Velocity accuracy | 0.05 m/s |
| Heading accuracy | 0.3° |
| Acquisition | Cold start 26 s, reacquisition 2 s |
Add the GNSS channel to your REXDESK configuration and set its rate and options. See REXDESK: set up GNSS and the IMU.
Watch: Set up GNSS and its advanced options using REXDESK (2:17)
Record acceleration and rotation
An internal 6-axis inertial measurement unit (IMU) combines an accelerometer and a gyroscope. Both record at up to 1 kHz, sampled independently of the CAN channels.
| Sensor | Full-scale ranges | Logging rate |
|---|---|---|
| Accelerometer | ±2, ±4, ±8 or ±16 g | Up to 1 kHz |
| Gyroscope | ±125, ±250, ±500, ±1000 or ±2000 dps | Up to 1 kHz |
Add the Accel and Gyro channels in REXDESK and choose a range for each. Choose the smallest range that covers the largest motion you expect, so you keep the most resolution.
Watch: Set up the IMU using REXDESK (0:58)
Read the axes
The axis directions are printed on the lid: X+, Y+ and Z+, with Z+ pointing out of the lid. Note how the logger is mounted. You can then relate the X, Y and Z channels to the vehicle's own axes when you analyse the data.
Wake on movement
REXGEN 2 IMU GNSS wakes on CAN traffic, and it can also wake from sleep when it is moved. Unattended logging then starts when the vehicle does. To set the sleep and wake options, see REXDESK: sleep and wake settings.
Motion, position and bus data share one timeline, so you can set triggers on the motion channels and reconstruct an event after it happens. Log files are power-safe, so the log survives a power loss at the moment of impact.
Back to the start of this series: REXGEN 2 and REXGEN 2 IMU GNSS: overview and specifications.
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