Very good CO2 Sensor.
For Open CO2 Sensor
After I got scammed with a 6in1 CO2 HCHO TVOC unit XY-T02 that claims to measure Co2, but actually doesn't as it has just 1 analog sensor for TVOC that is used to determine a fake CO2 value, I did some research and bought the OpenCO2 sensor.
And I am not disappointed. The Co2 values are reasonable, the build quality is good and the epaper display is fantastic. While the XY-T02 just lasted 6h on it's internal battery as the TFt display eats a lot of battery, the OpenCo2 sensor now operates for 8h and hasn't lost 1% battery.
The epaper display is sharp and more convenient than TFT, despite being black and white.
The USB cable that came with it for charging has a magnetic connector to a USB adapter plugged in, which is smart. Way harder to rip out the USB-C jack when the magnetic adapter gives away first.
The Co2 readings are reasonable. When you exhale on it (breath has 5% Co2), the value explodes as it should be. The fake unit does that too, as it measures organic components in the air, and it assumes if the organic components go up, the CO2 is high too. Breath contains a lot of organic components. So the Co2 explodes too on the fake unit. BUT. The fake unit always shows 450.-500ppm CO2 when not being blown at. It's not going up in my small, unvenitilated chamber which isn't plausible. The OpenCO2 sensor actually started at 1100 in my small room, going down to 600 after ventilation. But it's astonishing how fast it went up again to 1300. it took just 4h with windows closed. Which is plausible.
When I put the openCO2 sensor outside, it went down to just 520ppm. I expected 420ppm, the global normal today after humanity burned all that fossile fuels, but I guess living in a city with a lot of cars near a road comes with higher CO2 ppm's.
Will take it on a trip into the Eifel to see what it will report in the woods. Should for shure show 420ppm there.
But again, very reasonable results.
The final test to check if it doesn't just esimate CO2 by using a organic components sensor is putting a perfume bottle next to it.
Perfume, unlike breath, does nothing to the CO2 concentration. While breath has organic components and very high CO2, perfume just releases a lot of organic components. So when I open up perfume next to the fake unit, it shows exploding HCHO TVOC and CO2 values, as they are all determined by 1 analog sensor ouput for organic.
When I open the perfume next to the OpenCo2 sensor, nothing happens, the CO2 stays constant. So it passed the fake Co2 by THOC-Sensor test masterfully.
The temperature value is very accurate, fits the precision thermometer value. +0,2°C, better than the +-0,8°C stated in the datasheet.
Humidity seems to be off the mark though. While no humidity sensor shows the same to another humidity sensor, as inaccuracy is about 3-5% on most units, the open CO2 is about 6-9% off on 2 of my other humiditysensors which are pretty close to each other
The sensor datasheet gives following performance figures:
15 °C – 35 °C, 20 %RH – 65 %RH ± 6 % RH
-10 °C – 60 °C, 0 %RH – 100 %RH ± 9 % RH
Currently showing 62%, the others 54% and 55%, at 24,8°C. So should be in the operating range of +-6% accuracy. But on the wider temperature range, could be as bad as +-9%:
The bresser Temp/hygrounits have +-5% on the whole range, so significantly better.
The reaction to breath is also unexpected. breath is very humid, but the humitity reading doesn't really change. 1% up is not what I would expect from breathing onto it.
So the humidity sensor is not the strength of this unit and could be way off.
But still happy. Really interesting how fast the air gets bad in my small room. Will shurely teach me to ventilate more often.
Cudos to the developer!
Update:
The Firmware is regularily updated and I got a lot of new functions:
5.2 ist really good, different fonts, inverse, History as graph and best of all: A webinterface with an excellent graph of the last 24h.
Really, really good. Very pleased with it.
