Accuracy of the VMB1TS

I have 3 vmb1ts sensors whereof the accuracy is bad. I have to calibrate the sensors on the TC several times a week.
The measurement keeps changing between 17 and 23°C while it should be 21,5°C.

I found this topic covering the same problem, but there aren’t any solid solutions there.

Are there other people experiencing these problems and is there anyone with a solution?


The sensor can be placed too close to a heating source.
Air flow can also be a reason for the fluctuation, sometimes from inside de wallmounted box.

since few days I check my temperatures in many room ( and I think WMB1TS aren’t accurate :imp:
My first experience was (1 alcohol temp sensor + 1 electronic sensor) near VMB1TS : two first are OK but VMB1TS shows big difference.
In fact, we could change offset but not gain : f(x) = ax+b where b = offset, x is raw temp and f(x) should be real temperature

Then, always with the same temperature placed near WMB1TS (Salon) shows me it has a gain too big (06 february, ext temp : -7°C, VMB1TS on a wall contigous to exterior) : 19°C(T) = 19°C(Velbus)
24°C(T) = 25,5°C(Velbus)

My question is now :

  1. can Velbus upgrade VMB1TS with a gain parameter :question:
  2. how can we correct this (without self-programming) :question:

For information, I’ve got 11 VMB1TS (on website it miss external one and office one)
[size=85]PS: I feel like having “Hubble telescope” in my house [/size] :cry:

I’m experiencing the same problems here, fortunately temp in my home only fluctuates in about -1 to +1 °c around 21.5°C so I calibrated the offset at that 21.5°C. Gain starts to be inaccurate when temp rises above +2°c of -2°c…