I have a pokeys57e which has support for up to 55 1-wire sensors. I would like to use this to measure temperature and humidity in multiple places around the house. I have purchased three different DHT22 (temp/humidity sensors) from different . One of which was DOA, the remaining two have wildly different humidity readings.
dumb question but… where is the other sensor located? Could be that much difference in humidity? Sort of stands to reason it would be drier in unfinished basement. Only 8% difference. I have a monoprice motion sensor in the bathroom which has a humidity sensor and persistence shows rise in humidity when shower runs 10 - 15%
Why not get a cheap analog gauge (like patio/garden thermometer type sometime has) to check against.
I’m afraid you have a mistake here. Logically, two DHT22 should deliver the same readings. Unfortunately they don’t. Their technology prevents that. The 8% difference can be explained quite loosely by the, even small, spacing, resistance of the circuits and the underlying functionality of the DHT22. The BME280 is a bit more accurate, but more expensive. And if you want really good, reliable values, you have to look in completely different price ranges.
When it comes to air humidity, it should not be forgotten that there is not one value per room. Put a sensor in each corner of one room (top and bottom) and you will get 8 completely different values. I had to learn that the hard way. My highest durable difference in one room was 45%…
It’s also worth pointing out that they only have an accuracy of 2-5% so it is within the error range to have up to a 10% difference between two sensors.
You can monitor them against a standard sensor to see if they are consistently off and apply an adjustment. But you also need to think about your use case. does it really matter if they are 2-5% off? If so, you probably need to purchase better sensors.
Do better 1-wire temp/humidity sensors exist? I have seen some i2c sensors that are claimed to be more accurate - however my understanding is that i2c is only for short distance which would make home running difficult.
I am currently using the BME280 sensor connected to an esp8266 for remote sensing and it matches up closer to my second BME280 then the DHT22 ever will. I have used the DHT11 and DHT22. Cheap and easy sensors but not very accurate.
