Serial MODBUS Gateway - Advanced Sensor Configurations

While Monnit does provide details on sensor data interpretation using the Serial MODBUS Gateway, many sensors offer Advanced Configurations for which modifications are not supported on the Serial MODBUS Gateway. The rationale for this is the potential for a misconfiguration to render the device not optional. This can be a hurdle in some applications which require the modification of some of these configurations. Since there is no public document which outlines these registers and values, there is a workaround using the REST API in the iMonnit Online Portal which might help you to utilize the Advanced Settings in most sensors.

If you add the devices to an account in, then enter the configurations in the user-interface and save, you can use the REST API to request the values entered for these configurations. These values can subsequently be used to write to the associated registers in the MODBUS interface.

For example, if you save the desired configurations in iMonnit, then use the REST API methods SensorGetExtended and SensorGetCalibration, you can retrieve the Hysteresis, Low Threshold, High Threshold, Calibration 1, Calibration 2, Calibration 3, and Calibration 4 values to write to your sensors (offsets 26/27, 28/29, 30/31, 32/33, 34/35, 36/37, 38/39 respectively as per the Serial MODBUS User Guide page 27) .

Please be advised that these 32 bit values are split into two 16 bit registers, and to observe the process for writing both 16 bits of the register. Please refer to the Serial MODBUS User Guide if you are not familiar with this.

If you are unable to retrieve the values, please enter the configurations in iMonnit Online and reach out to The current values can be provided if requested.

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