I am planning to buy a formaldehyde sensor and I would like to connect it to an Arduino Uno board (and later to a Raspberry). As far as I know, the sensor comes in a small box/bag without any other external components (e.g. amplifiers etc.). So I will end up having in my hand a sensor with two copper terminals for connection (see image below):

enter image description here

Is it possible to connect this to an Arduino board without having a connection scheme? If yes, where do I connect the two terminals of this sensor to the 5V, GND and the A## ports? Also, how to translate the voltage coming from the sensor to ppm (parts per million) only by having general specifications from the manufacturer and not some kind of table of conversion? Also, would I need an external component for this? If yes, which component?

I know that this question sounds very stupid, but so far I've used sensors that come with a code on Seeed Grove with a clear description and I assumed that the code is there because there is a link between the producer of a certain sensor and Groove. Thank you!

FYI: The producer writes some things about the sensor but that doesn't help me a lot:

This sensor is of the two-electrode electrochemical type, operating by the diffusion principle and as such requires no external sampling hardware. In the presence of formaldehyde gas a small direct current is produced; the sensor requires no power supply of its own but this current requires amplification to make it readable using external data collection equipment.

  • 1
    Step one: read the datasheet. Step two: implement the circuit described therein.
    – Majenko
    Dec 11, 2017 at 19:38
  • buy the sensor kit
    – jsotola
    Dec 11, 2017 at 19:39
  • I would gladly buy the kit, but I'm afraid I would end up with the same problem. How would I connect the kit to an Arduino board? As for implementing the circuit, well, I don't have the right knowledge. You are referring to the one with resistors and capacitors, right? (I can only read some of the symbols in the circuit schemes)
    – Physther
    Dec 11, 2017 at 19:44

1 Answer 1


You have linked to the datasheet of the sensor.

In the datasheet, look at the "Application Circuit" section. You must build this circuit. The sensor produces a very small electric current, and the application circuit is high-gain amplifier to translate that very small electric current to a varying voltage you can sample with the Arduino ADC.

Note on the circuit, the wire labled "To ADC" -- that is the part which you connect to your arduino.

As for calibration, the datasheet itself notes that the process is non-trivial, or that they can perform a calibration, for an additional fee, at the time you order a batch of sensors. Presumably their calibration will include the precise resistor values used to set the gain of the amplifier, and also an equation to associate PPM values to the analog voltage provided at the "To ADC" wire.

As for reading the circuit diagram (schematic), you may already know resistors and capacitors. For the other items, search online for the part numbers given, to find out what they are.

The datasheet also notes that the application circuit is available pre-built from the sensor manufacturer. You may want to contact them to determine how to purchase one for yourself.

Most electronics products have a datasheet that explains all you typically need to know about the device, such as it's operating parameter minima and maxima, typical values, typical outputs, etc. This sensor is no different, except that the calibration procedure is not described in great detail due to the complexity.

  • Thank you for the nice answer. Do you know if the Kit they offer on the website is composed of that extra circuit from the datasheet or it is a different circuit? Otherwise, I will ask them to send the sensor together with that particular circuit. Thank you for clarifying this.
    – Physther
    Dec 11, 2017 at 21:02
  • Read their website. In the Accessories section is the interface circuit board. I do find it hard to believe that a Q&A website is need to read information that is freely available and linked to already!? Dec 11, 2017 at 21:23
  • It's not only about reading it. It's also about understanding. I'm a noob in electronics and that's why I am dealing with this. The interface circuit board doesn't have a scheme that would make me understand that it is the one in the specs. That's why I need help. Thanks to you it is now clear how to connect that circuit to an Arduino. If that accessory is the circuit that I would have to build, then I will just get it.
    – Physther
    Dec 11, 2017 at 21:30

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