Comparison CO2 sensors MH-Z19B vs Senseair S8

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

In this CO2 meter I used a Chinese CO2 sensor MH-Z19Bcheap and good value for money.

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

And, while I'm deciding, I thought it would be best to start with a comparison CO2 MH-Z19B vs Senseair S8to analyse 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 newer MH-Z19C, taking into account their differences. You can find their differences, and more information about this sensorin the following article:

The CO2 sensor bible MH-Z19B

The CO2 sensor MH-Z19B

I leave you here the datasheet of the MH-Z19B

The Senseair S8 LP CO2 Sensor

I leave you here the datasheet of the Senseair S8 LP

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

Comparison of parameters MH-Z19B vs Senseair S8

Model	MH-Z19B	Senseair S8 LP
Technology	NDIR	NDIR
Gas detected	Carbon dioxide	Carbon dioxide
Accuracy	±50 ppm and ±3% of the reading	±40 ppm and ±3% of reading
Operating voltage	4.5 ~ 5.5 VDC	4.5 ~ 5.25 VDC
Medium current	< 60 mA (@ 5V supply)	18 mA
Maximum current	150 mA (supply @ 5V)	300 mA
Interface level	3.3 V (5V compatible)
Measuring range	400 ~ 2000ppm 400 ~ 5000 ppm	400 ~ 2000 ppm 400 ~ 10000ppm (in extended range)
Output signal	Serial (UART) - TTL level 3.3 V - Analogue output PWM	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	9 mm×33 mm×20 mm (L×W×H)	8.5 x 33.5 x 20 mm
Weight	5 grams
Life	> 5 years	> 15 years

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

It should be borne in mind, moreover, that the MH-Z19B is a Chinese productwhile the Senseair S8 is a Swedish product.. I'm sorry, but I trust the parameters provided by a Swedish manufacturer much more, especially in cases like this, where checking the accuracy of the parameters provided by the manufacturer is not available to everyone.

Differences beyond the parameters

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

In this type of sensors, the measurement is not obtained directlysuch as in the case of a mercury thermometer, but it is not a "deduces". of certain "effects".

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

In addition, this measure is temperature-dependent (and to a lesser extent humidity) and of its proper calibration.

This is as far as I wanted to go, calibration.

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

Although these sensors are factory calibrated (and I assume, as an act of faith(the Senseair one is better calibrated), this calibration changes with use. The infrared lamp inside loses its effectiveness, the scatter detector loses its sensitivity, etc.

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

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

In this case, Senseair is so confident in its self-calibration process that they say, and I quote: "Thanks to our self-calibration function, you can mount sensor and forget about it for the next 15 years and it will still be accurate.".

Sensor variations

Both sensors are available in several versions, so it is important to know which version is most suitable at any given time.

Variations of 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 2000, 5000 and 10000ppm versions. In general, for domestic use, the ideal is 5000 ppm.because it is quite easy to exceed 2000 ppm in a house.
3. Sensors are available with a black printed circuit board instead of green. These versions are false. You can find out more in the article on MH-Z19 sensors I wrote with all the details.

Senseair S8 Variations

1. Part No: 004-0-0050 - S8 2% - For pin connection (for alarm and control applications)
2. Ref. No.: 004-0-0013 - S8 - Residential for pinless connection (for ventilation control and CO2 monitoring)
3. Ref. No.: 004-0-0056 - Senseair Residential - For pin connection (for ventilation control and CO2 monitoring)
4. Ref. No: 004-0-0017 - S8 5% - For pin connection (for alarm and control applications)
5. Ref. No.: 004-0-0053 - Senseair S8 LP - For applications where both power consumption and accuracy are critical factors

It is important to understand the different variations if you are going to buy one. For our CO2 monitoring application the ideal 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		About 25 Euros for the CO₂ sensor Senseair S8 LP on this AliExpress link. It is a shop with quite a few units sold and a five-star rating, left by buyers in the reviews. The shipping is by AliExpress Standard Shipping (the new 10-day shipping method to Spain), so you should have it at home in about two weeks.
MH-Z19B		About 18 Euro CO₂ sensor MH-Z19B in this AliExpress link. It is a shop with many positive reviews and the shipping is by AliExpress Standard Shipping, so you should have it at home in about two weeks. I recommend you order the one with a 5000 ppm range. * I am removing the link, for the time being, 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's more expensive, but if you want it quickly, you will have it at home in 24 Hoursin many cases.

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

Well, the truth is that I can't say for sure.

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

I can tell you that the ESP Easy supports the Senseair S8 LP, so following the tutorial to build the Easy CO2 meter with the MH-Z19Band by 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 you can do it too. You can find it here:

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