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Attaching the CJC Circuit of an STA-1800HC
4-5
Attaching the CJC Circuit of an STA-1800HC
The STA-1800HC contains a CJC circuit that develops a voltage directly
proportional to the temperature of the STA-1800HC screw-terminal
blocks. At 0˚C, the CJC circuit output is 0V; the output changes at the rate
of 10mV per ˚C. The CJC circuit is represented by the schematic in
Figure 4-4.
Figure 4-4. CJC Circuit Schematic
As Figure 4-4 shows, the CJC circuit output appears across the TB11
screw terminals. TB11 is located as shown in Figure 4-5.
Figure 4-5. Location of CJC Circuit Screw Terminals (TB11)
You can determine the CJC temperature by wiring TB11 to the screw
terminals of an unused analog input channel and reading the CJC circuit
voltage. Convert this reading to a temperature value you can use to offset
thermal error introduced to thermocouple readings at the STA-1800HC
screw terminals.
LM35DZ
TB11
CJC
Out
CJC
GND
0.1µF
27
Ω
+15V
1
2
3
0mV = 0˚C
10mV/˚C
STA-1800HC Accessory
Terminal block TB11 for
CJC circuit
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