Campbell 3WHB10K, Product Manual

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Table 3-1: 3WHB10K connections to Campbell Scientific data loggers
Function Label/Wire
GRANITE
analog input
module
GRANITE 6,
CR6
CR3000,
CR1000X,
CR800, CR850,
CR1000
CR9000X
Excitation Black wire X1 U5 VX1 Excitation 1
V1 high
reference
H 1H U1 1H 1H
V1 low sense L 1L U2 1L 1L
Ground G ⏚ ⏚ ⏚ ⏚
1
The GRANITE 9 and GRANITE 10 do not directly make analog measurements. Instead, they use analog input
modules such as the VOLT 108 or VOLT 116. When making a half-bridge measurement, the terminal input module is
connected to the analog input module, which is then connected to the GRANITE 9 or GRANITE 10.
4. Programming examples
The following examples show the two instructions necessary to 1) make the measurement and 2)
calculate the temperature. The result of the half bridge measurement as shown is R
s
/R
0
, the input
required for the PRT algorithm to calculate temperature.
If using a calibrated sensor, the exact measurement of R
0
will be known. Use this value to
increase the accuracy of the PRTCalc() instruction by inserting the following equation
between the
BrHalf4W()
and
PRTCalc()
instructions in the example programs.
Rs_R0 = Rs_R0*100/R0
where R0 is the sensor resistance at 0 °C
The following examples are based on a maximum sensor resistance of 100 Ω at 0 °C. The
excitation voltages used were chosen with the assumption that the temperature would not
exceed 50 °C. Calculation of optimum excitation voltage is discussed in
Excitation voltage (p. 8).
3WHB10K 3-Wire Half Bridge Terminal Input Module 4