There is a software bug on the IMU-KVH1750 that can intermittently trigger bad health statuses on the IMU gyros.
The bad health status results in a loss of all INS functionality and causes the SPAN system to reset.

Products Affected:
IMU-KVH1750 – units shipped before September 6, 2016 with serial numbers starting from 1510k013
Affected Firmware Versions:
ICB DSP Rev D Version 4.03
ICB FPGA Rev: 0x0a

A software bug has been identified on the IMU-KVH1750 in which the gyro health status is being erroneously flagged as bad. The unhealthy status flag will cause all INS functionality to be lost and initiate an immediate SPAN system reset. The issue is intermittent as some IMUs may fail out of factory, or may be exacerbated when placed in strong magnetic conditions. The root cause, as identified by KVH, is magnetometer data uncalibrated for the KVH1750 is exceeding error thresholds and triggering incorrect gyro status failures.

A field-upgradable firmware has been provided by KVH and has been verified by NovAtel. The firmware files, instructions, and Windows PC loader program are available at the following link: A direct RS-422 serial connection to the IMU capable of 921600 baud is required for the firmware load.

Affected customers have the option to load the new firmware by either using the instructions provided or via RMA through NovAtel’s support channel. Units with serial numbers before 1510k013 are not affected by this software issue and cannot be updated with the new firmware.

New Firmware Versions:
ISB DSB Rev E Version 4.14
ICB FPGA Rev: 0x0b

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