After installing some VW instruments, we had to cut the cables to connect to the data logger. Do we need to adjust the RTD offset, and if so, how can we do this in the field with all the instruments installed?
For many, this question is not relevant. Our VW piezometers are almost always shipped with thermistors rather than RTDs.
For those with older VW piezometers: T he VW sensor calibration record lists an RTD offset based on the original length of the cable that was attached to your sensor. If you change the length of the cable, you must adjust the offset. Use this table to find the change in offset for a given change in cable length. If you have shortened the cable, subtract the change in offset from the original offset. If you have lengthened the cable, add the change in offset to the original offset. Note that the vibrating wire part of the signal (the pressure measurement) is not affected by cable length.
Also, take a look at the most recent version of the VW piezometer manual for a discussion about whether you really need to go through these steps.