One of my VMBGPO modules (build 1720) has a tempeature offset of 2°C. Is this normal?
I checked this by comparing the temperature with those from 2 other sensors at the same location.
It’s a minor calibration issue.
All you have to do is decide which device is telling the truth about the room temperature and calibrate the others to match.
(Calibration is done within VelbusLink for each device, just look for the offset, which is in the same place as minimum switching time, hysteresis)
I once got sent a photo of three digital thermometers showing three (subtly) different temperatures along with the question… “Quick one is correct?”
To this day , I’m still not sure what the correct answer is.
Hi MDAR,
That’s exactly what I did: calculate the offset comparing with two other sensors of which I know the specs. In this case those two did display more or less the same values.
I usually work with sensors with a max deviation of 0,5°, so 2° looks extreme to me.
Hi
I’ve lost count of how many Velbus thermostats I’ve commissioned, but you’re right.
0.5° deviation is not uncommon, 2° is unusual.
Once calibrated, I’ve never had a problem with the accuracy.
FYI
It is possible to get 0.1° resolution from the temperature sensors.
Is it the “Hysteresis” parameter under “Temperature Senor => Advanced => Adjustments => Hysteresis” to adjust the resolution parameter to 0.1° ? Is there a datasheet somewhere what the specs are that are embedded within these modules?
Hysteresis is not the same as resolution, so I assume the answer is no.
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As @PrzemoF say, no thats for the decision making of the thermostat channel switching.
The 0.1°c resolution reporting is provided with a bus packet as standard.
You just need a way to decode it.
A raw Velbus node in NodeRed will be enough.
Or a function node monitoring a TCP connection.
All the information about the protocol and module commands / packets can be found on the official GitHub page
Feel free to ask any questions
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