Comparison of CO2 sensors MH-Z19B vs Senseair S8

Last modified 1 year

The tutorial to build the CO2 Easy meter, which I wrote recently, aroused a lot of interest, getting more than 8,000 visits in its first month.

In this CO2 monitor I used a Chinese CO2 sensor MH-Z19B, cheap and good value for money.

Thinking about how to improve the meter using a sensor, also inexpensive, but higher quality, I have decided to evaluate the possibility of making an improved version of the CO2 meter with the Senseair S8 LP CO2 sensor, of Swedish origin.

And while I make up my mind, I thought it best to start with a comparison MH-Z19B vs Senseair S8 CO2 sensors, to analyze their similarities and, above all, their differences.

This comparison is made with the MH-Z19B but is equally valid for the original MH-Z19 and the more recent MH-Z19C, taking into account their differences. You can find their differences, and more information about this sensor, in the following article:

The MH-Z19B CO2 Sensor Bible

The MH-Z19B CO2 Sensor

I leave you here the datasheet of the MH-Z19B

The Senseair S8 LP CO2 sensor

I leave you here the datasheet Senseair S8 LP

Description of serial protocol (modbus) of the Senseair S8 LP

MH-Z19B vs Senseair S8 specs comparison

Model	MH-Z19B	Senseair S8 LP
Technology	NDIR	NDIR
Gas detected	Carbon dioxide	Carbon dioxide
Precision	± 50 ppm and ± 3% of reading	± 40 ppm and ± 3% of reading
Operating voltage	4.5 ~ 5.5 VDC	4.5 ~ 5.25 VDC
Average current	<60 mA (@ 5V supply)	18 mA
Peak current	150 mA (supply @ 5V)	300 mA
Interface level	3.3 V (compatible with 5V)
Measuring range	400 ~ 2000ppm 400 ~ 5000 ppm	400 ~ 2000 ppm 400 ~ 10000ppm (in extended range)
Output signal	Serial (UART) - TTL level 3.3 V - PWM analog output	UART (Modbus)
Preheating time	3 minutes
Measuring range	5 seconds
Response time	T90<120s	2 minutes for 90%
Operating temperature	0 ~ 50 ° C	0 ~ 50 ° C
Operating humidity	0 to 95% RH (non-condensing)	0 to 85% RH (non-condensing)
Dimensions	9mm × 33mm × 20mm (L × W × H)	8.5 x 33.5 x 20 mm
Weight	5 grams
Lifetime	> 5 years	> 15 years

In view of these parameters, the Senseair S8 is indeed somewhat better than the MH-Z19B.

It must also be taken into account that the MH-Z19B is a Chinese product, meanwhile he Senseair S8 is a Swedish product. Sorry, but I trust a lot more to the specifications provided by a Swedish manufacturer, especially in cases like this, where checking the accuracy of the specs provided by the manufacturer is not within everyone's reach.

The differences beyond the specs

In addition to the specifications, which, on paper, can be very interesting to know, there is a very important aspect, and this is the internal firmware, that makes them work.

In this type of sensors, measurement is not obtained directly, as may be the case with a mercury thermometer, but rather it's "Deduced" from certain "Effects".

In the case of these sensors with NDIR technology, the measurement consists of quantifying the scattering that occurs in an infrared beam when it passes through the air in its tiny measurement chamber.

Also, this measure is temperature dependent (and to a lesser extent humidity) and its correct calibration.

Here is where I wanted to get: calibration.

Calibration is what makes the difference, really, between having correct measurements or not.

Although these sensors are factory calibrated (and I assume, as an act of faith, that the Senseair comes better calibrated), this calibration varies with use and wearing. The infrared lamp inside it loses its effectiveness, the scattering detector loses its sensitivity, etc.

In this way, these sensors periodically self-calibrate to adjust your measurements, and it is your firmware that takes care of doing it.

In this case, it seems, from what users of the sensor manufactured by Senseair (I have not used it yet) say, that its calibration firmware is much smarter / accurate than the MH-Z19Band this, my friend, does make an important difference.

In this case, in Senseair they are so sure of their autocalibration process that they say, verbatim: «Thanks to our self-calibration feature, you can mount sensor and forget it for the next 15 years and it will remain accurate«.

Sensor variations

Both sensors have several versions, so it is important that we know which version is more appropriate at all times.

Variations of the MH-Z19B

1. There are several different models of the MH-Z19 (at least four), discover them all in the MH-Z19 bible.
2. There are versions of 2000, 5000 and 10000ppm. In general, for home use, the ideal is 5000 ppm, because it is quite easy to go over 2000 ppm in a house.
3. There are some sensors with a black printed circuit board instead of green. These versions are false. You can know more in the sensors article MH-Z19 false that I wrote with all the details.

Senseair S8 variations

1. Reference: 004-0-0050 - S8 2% - For connection via pins (for alarm and control applications)
2. Reference: 004-0-0013 - S8 - Residential for connection without pins (for ventilation control and CO2 monitoring)
3. Reference: 004-0-0056 - Senseair Residential - For connection via pins (for ventilation control and CO2 monitoring)
4. Reference: 004-0-0017 - S8 5% - For connection via pins (for alarm and control applications)
5. Reference: 004-0-0053 - Senseair S8 LP - For applications where both power consumption and accuracy are critical factors

It is important that you understand the different variations, if you are going to buy it. The ideal one for our CO2 monitoring application is number 5, "Senseair S8 LP".

Comparing the components in the links that I propose in AliExpress, with shipping from China, the costs would be:

Senseair S8 LP		Some 25 Euros for the CO₂ sensor Senseair S8 LP in this AliExpress link. It is a store with quite a few units sold and a five-star rating, left by buyers in the opinions. Shipping is by AliExpress Standard Shipping (the new mode of shipping to Spain in 10 days), so you should have it at home in about two weeks.
MH-Z19B		Some 18 Euros for the CO₂ sensor MH-Z19B in this AliExpress link. It is a store with many positive reviews and shipping is by AliExpress Standard Shipping, so you should have it at home in about two weeks. I recommend that you ask for the one with a 5000 ppm range. * I remove the link, for now, until I get another source of some confidence.

If you don't want to wait that long, you have the option of buying these components on Amazon, with fast shipping. It is more expensive, but if you want it quickly, you will have it at home in 24 hours, in many cases.

Will there be a project with the Senseair S8 LP in eMariete?

Well the truth is that I can not completely assure you.

I would like to do it, but the truth is that I already have three CO2 meters at home (a Netamo, one with the MH-Z19 and another with the MH-Z19B) and I don't need more.

Yes, I advance you, that the ESP Easy supports the Senseair S8 LP, so following the tutorial to build the CO2 Easy meter with the MH-Z19B, and making the appropriate changes, you should have no problem getting it to work.

And don't forget to subscribe to the eMariete Newsletter, so you won't miss any news.

Update: I have already done the project with the Senseair S8 LP and it is documented so that you can build it too. You can find it here:

Easy CO2 Meter with ESP8266 (NodeMCU) and Senseair S8 Sensor