CO2 Sensor SKU: SEN0159: High analog output voltage readings

I have Runlinc Stemsel E32W microprocessor which has bulit in Wi-Fi module. I have connected the +ve of the Co2 to the 5V io25 (Runlinc), the -ve of Co2 to GND in io33 (3V) and the A of Co2 to the 3V.

I have uploaded the image which shows connection (Blue wire is the +ve, Red Wire is the -ve and Brown wire is the A in CO2 sensor).
And another image is attachedd showing the Runlinc online IDE which shows the current readings.

  • When the analog output is less than 142 then the LED in Co2 turns on and vice versa.

  • When I breathe near the sensor, the value drops but doesn’t go below 100.

Now, what I want to know is according to the datasheet of MG-811 provided by the core-electronics, the output value should be in range of 30-50mV ( 350—10000ppmCO2). Why is the voltage output readings too high?
This is the datasheet from core-electronics.

I have attached a datasheet specification of MG-811 from a different website url: : Here, the output voltage is 100-600mV 400-10000ppm CO2.

Hi Kabir
I am not familiar with any of this but the first thing I noticed is you have said you have connected the sensor output to 3V. Why would you do this. Surely the sensor output should be connected to an input of the processor???
Cheers Bob

OP has misspoke. The brown wire is connected to D33, as suggested in the connection diagram.

Hi Kabir,

Welcome to the forum :slight_smile:

I’ve had a look through the manufacturer’s documentation and it looks like they recommend keeping the unit powered on for 48 hours the calibrating it before you will get an accurate measurement from it. I think this is because the unit has an internal heater that runs to improve the measurement accuracy and there may be some initial settling time required for the electrochemical sensor inside.

You can find the calibration process here:

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