[DHT22]

what do you mean by "important differences" ?

Bye Jack

Thanks for your answer. On a old (needle ) hydrometer we read 80% while the DHT indicate 70%

I have build 2 devices The first indicate 70% while it should be closer to 80% The other indicate 51% which seems very low to me.

I have checked the 5 volts - ok on both grounding OK

The checksum is always correct. At the beginin I had a bad contact giving every now and then a checksum error, so I am sure the function is ok!

Seems to me that If the checksum is ok, the DHT has actualy send the wrong data, and the mesurement is wrong!

ON one device the DHT is read every 2 second, that's maybe to short?? One the other device it's read every 7 second (about)

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I forgott to indicate: at the begining, this device indicate humidity that's loocked correct. It's only later, after a few weeks, that it began to slowly give lower results seeming wrong.

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The problem with trying to answer question like this, is we have no idea how you wired up this simple device or how you wrote your code.

There are many tutorials on the web and may give you some insight in what you may need to do.

First time:

- Smoke came out and circulated counter-clockwise Second time:

- Smoke turned clockwise! WTF?

There are several possible reasons for your problems: If the results are OK at first and go wrong over time it could be contamination (most likely), crap sensors (you are using the cheapest part you can get !!) or incorrect power supplies/operation.

Because it has built in electronics it's hard to see how your software would mess it up (but not impossible) - this type of sensor doesn't like a DC bias so it is just possible that running it in an odd way could cause that.

Michael Kellett

Many thanks for your answer. What do you think about the SHT10 and alike. As I said I am retired and do all this just for 'fun' and can't spend to much mony on this. But if I can replace the captor (DH22) by a SHT10? and do some rewiring and simply(?) change the program??

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