Sutron 8310 - Page 169

Sutron Corporation 8310 & 7310 Users Manual 8800-1125Rev. 2.7 (BETA) 4/16/2014 pg. 169
SwitchedPwr
None
Processing
Invert
Cal Slope
1
Cal Offset
0
M#.O1: MeasName
Right arrow into the output
setup
Field
Value
Processing
Add Slope-Offset
Slope
1000
Offset
-250000
Add Processing
Steinhart-Hart
A
8.271111e-004
B
2.088020e-004
C
8.059200e-008
This Campbell Scientific temperature probe has an additional resistor in series with the
thermistor an therefore requires additional processing steps to extract the thermistor resistance
Rt.
Rt = 1000 * (Vx/Vo) – (249000 + 1000)
The result of a bridge measurement is Vo/Vx, that is, the voltage output (analog input to the
8310) divided by the excitation voltage (Vref). Therefore the first processing step utilized is
“Invert” in order to obtain Vx/Vo. Additional processing is then added to the output. Adding
“Slope-Offset” processing with a slope of 1000 and an offset of -250000 finishes the calculation
of Rt.
An additional processing step, Steinhart-Hart, is then applied to convert the resistance to
temperature in degrees C. The Steinhart-Hart coefficients to be utilized are:
A = 0.0008271111
B = 0.000208802
C = 8.0592e-008
If the desired units of temperature was degrees F, then it would be possible to add another
Slope-Offset processing step with a slope of 1.8 and an offset of 32 in order to convert the
degrees C to degrees F.
Barometric Pressure Sensor
The following setup is for the Sutron ACCUBAR 5600-120 barometric pressure sensor.
Wiring
Sensor Wires
Function
Connection
Barometer Terminal
block terminal 4
Power
SDI-12 PWR
Barometer Terminal
block terminal 5
Ground
SDI-12 GND
Barometer Terminal
block terminal 6
Data
SDI-12 DATA
Measurement Setup