The unit of concentration

[Akshul-pirhoalpha]

@dpeaslee
My inference from the testing of sepc so2 ulpsm -

1. If the sensor is off for a long time 3-4 days, then it needs 4-5 hrs to stabilize
2. The current values (nA) varies by 20-30 nA after stabilization. Because of that the conc values vary 1-2 units.
3. I have done zero calibration of the sensor for multiple days. Even after zero calibration, the conc values went negative as well.
4. If the sensor is off for a few hrs then it stabilizes in 30 mins to 1 hr.
5. The range we are getting in clean office environment is 5-20 units, which is more close to ppb unit when compared air quality standards for so2. But in the firmware I have selected unit as ppm. Can you please check if the equations used are correct? Because if the sensor is indeed giving conc as 5-20 ppm then it is wrong.
6. The ulpsm board is very sensitive. It is interfaced with a mcu board. When I connected mcu board with pc to program it, then only the current measurement is varying a lot and going to negative values. Right now multiple snesors are interfaced to the mcu. It that the reason for such high readings if the equations are correct?

Please let me know about this. Thank you