Last modified December 23, 2020
He tutorial to build the CO2 meter, which 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-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 sensor Senseair S8 LP, of Swedish origin.
And while I make up my mind, I thought it best to start with a comparison CO2 MH-Z19B vs Senseair S8, to analyze their similarities and, above all, their differences.
The MH-Z19B CO2 Sensor
It is a very popular sensor among the electronics hobbyist community because it is relatively cheap, accurate enough and there are many projects on the internet based on it.
I leave you here the datasheet of the MH-Z19B
The Senseair S8 LP CO2 sensor
The Senseair S8 LP CO2 sensor is an inexpensive sensor of Swedish origin (although not as much as the MH-Z19B), with characteristics, on paper, better than the MH-Z19B.
I leave you here the datasheet Senseair S8 LP
Description of serial protocol (modbus) of the Senseair S8 LP
MH-Z19B vs Senseair S8 parameters comparison
|Model||MH-Z19B||Senseair S8 LP|
|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)
|exit sign||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|
|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 parameters provided by a Swedish manufacturer, especially in cases like this, where checking the accuracy of the parameters provided by the manufacturer is not within everyone's reach.
The differences beyond the parameters
In addition to the parameters, 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 "Deduces" of 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.
This is where I wanted to get, calibration.
Calibration is what Mark 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), with use this calibration varies. 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«.
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
- There is a MH-Z19 model and a MH-Z19B, which is a more modern and improved version. This version has, among other advantages, better precision (50 ppm + 5% of the measurement in the case of the MH-Z19 and 50 ppm + 3% of the measurement in the case of the MH-Z19B).
- There are 2000 and 5000 ppm versions. Usually, for home use, the ideal is 5000 ppm, because it is quite easy to go over 2000 ppm in a house.
- There is a 10,000 ppm version, but everything I discover so far, makes me think it's fake (a "Chinese copy of the Chinese original"), a counterfeit and predictably low-quality product, manufactured outside of its official manufacturer.
- There are some sensors with a black printed circuit board instead of green. As in the previous case, everything indicates that these versions are false, equally.
Senseair S8 variations
- Reference: 004-0-0050 - S8 2% - For connection via pins (for alarm and control applications)
- Reference: 004-0-0013 - S8 - Residential for connection without pins (for ventilation control and CO2 monitoring)
- Reference: 004-0-0056 - Senseair Residential - For connection via pins (for ventilation control and CO2 monitoring)
- Reference: 004-0-0017 - S8 5% - For connection via pins (for alarm and control applications)
- 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. Ideal 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 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.
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 meter with the MH-Z19B, and making the appropriate changes, you should have no problem getting it to work.
If you think I should do the project, leave a message in the comments saying why.
And don't forget subscribe to the eMariete Newsletter, so you won't miss any news.