DMI Connected to a CPT7

Figure: DMI to CPT7 Setup shows an overview of a DMI connected to a CPT7.

DMI to CPT7 Setup

The DMI connections are A+, A- and GND.

DMI Data Collected on the CPT7

Typical DMI hardware generates wheel ticks constantly as the wheel rotates. The CPT7 interface is configured to accumulate wheel tick counts at a rate of 1 Hz.

DMI Update Logic

DMI data is available through the RAWDMI log. The RAWDMI log can be used for applying DMI updates in post-processing.

The SPAN filter uses sequential RAWDMI logs to compute a distance traveled between update intervals (1 Hz). This information is used to constrain free inertial drift during times of poor GNSS visibility. The filter also contains a state for modeling the circumference of the wheel as it may change due to hardware changes or environmental conditions.

Information about how the DMI updates are being used is available in the INSUPDATESTATUS log.

Connect the DMI to a CPT7

The CPT7 DMI inputs are RS-422 differential inputs. Refer to Table: CPT7 Wheel Sensor Input Signal Levels for the required input voltages.

To connect a DMI:

  1. Connect the CPT7 I/O2 Cable, or custom interface cable, to the IO2 connector on the CPT7.

    For information about creating a custom interface cable, see CPT7 I/O2 Cable.

  2. Connect the DMI to the DMI A+ (Pin 14), DMI A- (pin 15) and GND (pin 8) connections on the AUX 2 connector.

  3. Connect an external power supply to the DMI.

    The power required for the DMI depends on the DMI used. Refer to the DMI user documents for more information.

Configure a DMI

  1. Send the following command to enable a DMI on the CPT7 wheel sensor inputs.

    DMICONFIG DMI1 ENABLE ENCLOSURE

  2. Send the following commands to log the DMI data.

    LOG DMICONFIGA ONCHANGED

    LOG RAWDMIA ONNEW

    LOG INSUPDATESTATUSA ONNEW

  3. Check the RAWDMI log to ensure the DMI is producing data.

  4. Check the INSUPDATESTATUS log to ensure the DMI is being used in the SPAN solution.

If there is no DMI data being produced or the DMI status is not USED, refer to DMI Troubleshooting.

For more information, see the DMICONFIG command, RAWDMI log and INSUPDATESTATUS log.