When your Mars Soiling Sensor readout displays NAN for Soiling Ratio or Transmission Loss, it means that the unit is waiting for a measurement result.


These fields will update properly once the unit is correctly configured (including latitude, longitude, and clock) and deployed outdoors in its installation location for a period including at least two hours before and after sunset. 


Note: For Modbus communication, reading a value of NAN for Transmission Loss and Soiling Ratio confirms that communication is established, but a measurement result is not yet available. As noted above, the device must be configured correctly and allowed to collect data overnight.


If Soiling Ratio and Transmission Loss values remain at NAN over multiple days, check the following:

  • Latitude and longitude are correctly set for the actual installation site of the Mars unit
  • The Mars unit's clock is correctly set to UTC time
  • The Mars unit is deployed in an open area with a view of the sky within a 30 degree cone angle
  • The Mars unit is continuously powered, including in the evening for at least 2 hours after sunset


For additional assistance, please contact Atonometrics.


Note: an upcoming software release will eliminate some of the requirements shown above, simplifying installation.