MHZ19

Project MHZ19
Some research into the MH-Z19 CO2 sensor
Status	Initializing
Contact	bertrik
Last Update	2016-10-22

Introduction

This page is about the MH-Z19 CO2 sensor and some experiments done with it.

This sensor gives a digital (serial) output of the CO2 concentration in air, in parts-per-million (ppm). It uses the optical measurement principle of measuring CO2, which should be much more accurate than the inexpensive electro-chemical sensors you can find. As far as I know, the optical measurement principle uses a broadband light-source to send some light through an air-sample. The sensor then looks at the relative intensity of the light at two different frequencies. The CO2 gas inside the air absorbs light strongly at very specific wavelengths, allowing a determination of the concentration (ppm) of CO2. This is then compensated for temperature and pressure for increased accuracy. See also wikipedia for this measurement principle. A new measurement is started every 5 seconds, you can actually see a small amount of light coming out of the sensor while it's measuring.

The MH-Z19 is the cheapest optical CO2 sensor I could find on AliExpress.