Procedure:
1. Do the procedure in
2. If there are values other than zero in the DVW Toolbox Steinhart-Hart Coefficients A, B,
and C columns for the sensor, write these down because you may need them later.
3. Set Steinhart-Hart Coefficients A, B, and C to 0.
4. Connect one wire from the temperature sensing element (it does not matter which one) to
either of the T terminals of the same input channel to which you connected the vibrating
wire sensor. Connect the other wire to the other T terminal. You should immediately see a
resistance value in the Static Thermistor column of DVW Toolbox. This is the resistance
value of the temperature sensing element. It is expressed in ohms (Ω). Check this resistance
against the documentation that came with your sensor to confirm that the correct
resistance is displayed for the current temperature.
5. Convert the measured resistance to temperature:
l
If the temperature sensing element is a thermistor, do the following:
o
Enter the Steinhart-Hart coefficients provided by the manufacturer into the
Steinhart-Hart Coefficients A, B, and C columns. The value in the Static
Thermistor column should now be the current temperature expressed in
degrees Celsius. For DGSI sensors, our C coefficient equals their D coefficient.
o
Set up the VWIRE 305 to convert the resistance to temperature by entering the
Steinhart-Hart coefficients into VWIRE 305 settings using DVW Toolbox,
Device Configuration Utility, or a program created with CRBasic Editor.
l
If the element is an RTD, do the following:
o
Some sensors use PRTs instead of thermistors. If your sensor is a PRT, find the
Calendar-Van Dusen coefficients on the manufacturers calibration sheet.
o
Add code to the program created with CRBasic Editor to convert resistance to
temperature. The PT100 PRT discussion in Campbell Scientific data logger
manuals may help you do this.
l
The other option for both thermistors and PRTs is to simply store the resistance data
then convert resistance to temperature on a computer after collecting data from the
field.
TIP:
It is good practice to preserve the original vibrating wire measurements when converting
them to temperature compensated values.
VWIRE 305
44
