[werk_ag]

..... find this line of code on the Pro2 PLUS RX or Pro2 Compact [Receiver] software: .....

This is a matter that I have considered raising for some time.  If the "error" is in the Transmitter hardware, then it would be more logical to "calibrate" the formula in the Transmitter software.  This is particularly relevant if you are using two (or more) transmitters (or receivers).

Hello Alan,

I understand your thought, however let me try to explain why this, as some other things too, aren't done at the TX level. As much as possible, I tried to minimize the number of  calculations done on the TX units. In almost cases where data is obtained using the Arduino ADC, what is sent to the RX is the ADC RAW reading, and the required calculations are done on the RX. This approach may have some disadvantages, but also have advantages, as it may be easier to do small changes on the RX software, compile it and reprogram the receiver, than do it on the TX unit which most of the times is installed on the roof.

Regarding the case we are talking about, in the TX parts list its clearly mentioned that for R4 (3K) and R5 (1K) should be used Metal Film resistors with 1% tolerance. Using this type of resistors the error on the measurement of Vbat voltage should be no great than 0.1V or 0.2V, which seems perfectly acceptable considering that the purpose of this reading is give the user a quick idea of the state of the battery.