2 EmonTH > UR and Temp differente reading

Submitted by truzzman on Mon, 25/04/2016 - 13:05

Hello

I have 2 EmonTH 1.4.

I test the reading closing in a tin box both EmonTH.

After some hours I can read different misures expecially for UR.

EmonTH A UR 38.2

EmonTH B UR 35.0

It's normal?

I also try a EmonTx 3.4 with a firmware for DHT22 reading. In the same condition of the two EmonTH i read only 29.5 UR.

Maybe bacause the +5 pin is always ON and there is the self-heating problem?

Thanks

Stefano

Submitted by truzzman on Tue, 26/04/2016 - 08:49.

Yesterday I made an experiment.

I closed in an ermetic box the two EmonTH with a little cup of salt and water. In these condition the the humidity in the box must follow this table:

T (C°) U (%) NaCl

10 75,6
15 75,6
20 75,4
25 75,2
30 75,0
35 74,8
40 74,6
45 74,5
50 74,4

The results are here:

The readings of both Emonth are a little under the value of the table, but with acceptable precision.

With other types of salt can be checked low humidity values, but NaCl is easy to find and the temperature of the test is not so important.

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