emonTHv1 Humidity

Hardware
1

Apologies if this has been mentioned before or if i am posting in the wrong section.

I’ve just received a couple of emonTHv1 as they were on sale i figured i’d pick some up. they’re sending the data to my emonbase and i’m able to log this on a local emoncms install.

However, I’ve placed one next to my next thermostat. The temperature reading is pretty much identical on both so i’m happy with that however the humidity seems to be quite far out. the emonTH registering around 31.5 and the nest at 48%, i believe the nest to be about right.

am i missing something?

2

I think it is on the old forum that there is a big discussion about the accuracy of the humidity sensor. I cannot remember all the details now. Try searching there.

3

Hi Robert,

Thanks for the advice. I’ll take a look there.

Just seems odd there is such a difference. I thought i may need to do something when logging.

4

Seems the accuracy is ±5% Max, however i’ve got nearly a 20% difference.

I do have 2 x emonth v1s that I’ve just received both have similar readings which indicated to me it could be something with the emonhub

5

Unless the “scales = …” numbers are different, then as far as I know, there is no mechanism elsewhere in emonHub to affect the calibration.

It is possible to obtain a point calibration using a saturated salt solution - details I think are again in the old forum. From what I remember, 2 or 3 salts are readily obtainable that will give the same number of fixed calibration points.

https://openenergymonitor.org/emon/node/2484#comment-13111
(It turns out, there are many more than 2 or 3, but some may not be easy to get hold of.)