Chapter 4 SPAN Operation
CPT7 and CPT7700 Installation and Operation User Manual v12
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Figure 30: 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 32: CPT7 Wheel Sensor Input Signal
on page 173 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
