The vibrating wire devices transmit in raw units: frequency and thermistor resistance. To automatically convert these values to temperature and pressure, the calibration coefficients of the piezometer and thermistor need to be configured.

Temperature configuration

There are two methods available for converting the thermistor resistance to temperature:

Steinhart-Hart equation - A, B, C are the required Steinhart-Hart coefficients

Beta equation - β: the beta calibration coefficient; R_0: nominal resistance of thermistor at 25°C

By default, the temperature is automatically calculated with pre-set Steinhart-Hart coefficients. The default coefficients are derived by applying nonlinear regression to the following HMA Vibrating Wire Piezometer (Model 1200) resistance temperature table.

Pressure configuration

For the pressure calculation, the required fields are:

F_0: initial frequency in linear units (Hz^2 10^(-3) )

T_0: initial temperature (°C)

C_P: pressure coefficient (kPA/(Hz^2 10^(-3) ))

C_T: temperature coefficient (kPA/(°C))

Unit of output pressure

When the temperature is unavailable due to a sensor error, the pressure is calculated without temperature compensation, i.e. C_T=0. After inputting the coefficients, select the date of when to begin the calculation of the temperature and pressure. Click Update and Recalculate to save and apply the changes.