How do I calculate linear factors (mx + b) using the data on my calibration record?

Please note that we no longer calibrate VW piezometers with this method, however the information is presented here for older piezometers that were calibrated utilizing the old method.

We’ve made an Excel worksheet called: vw-linear-factors-xls. Your calibration record gives frequency readings for 12 pressures. Enter these Hz readings in the frequency column, overwriting existing data. The spreadsheet converts calculates frequency squared readings and then applies Excel slope and offset functions to calculate an m factor and a b factor. These are labelled slope (m) and offset (b). You’ll need WinZip or some other archiving program to unzip the file.