3SP_SO2_20 CPackage110-602 sensor - how to wire

I have the 110-602 and the 110-508 gas sensors. I’ve read the data sheets and it is very unclear how I should wire these sensors. It has four working pins titled:
-working, reference, counter, working

I just want to be able to power it and get data out into a microcontroller. Can someone explain how to wire sensors of this type? Much appreciated.


Hello @luke.cecelon Thank you very much for your question today!

While I have not used these sensors myself, from what I’m seeing, it would appear that the two “Working” pins are connected. I did see an example circuit for these given in the datasheet we have linked on the 110-602 at the following link on page 3:

Also, in the example at the link below with a CO2 sensor with two Working pins, they were jumpered together:


Please let me know if you have further questions on these.


Hi luke.cecelon,

The link Justin gave provides a good basis for getting up and running as well as a reasonable solution to use with an Arduino for non-precision measurement.

If you need higher precision, the other document we attach on the product detail page, SPEC Sensor Operation Overview, goes into a bit more detail how the sensor operates and gives a recommended dual op-amp circuit for higher accuracy.

Note that both the sensors you mention are temperature sensitive, so you will need to measure temperature as part of your system and include that in your calculations to get accurate measurements. This is particularly true for the SO2 sensor at cooler temperatures, which can change by more than 20% at 0°C.

Further information on the topic can be found on the following eewiki page:


Also, for a simplified alternative, you might want to consider the 1684-1023-ND, which is a board including both the basic SO2 sensor plus the external circuitry required to give you an easy voltage output which can be directly measured by an Arduino analog pin.