Data Translation DT9800 Series, User Manual

Page: 119 / 162

Calibration
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Calibrating the Thermocouple Circuitry
Note: Ensure that the DT9805 or DT9806 module has been running
for about 1/2 hour (allowing the module to warm up) and that you
have calibrated the analog input circuitry using the procedure
described on
page 104 before calibrating the thermocouple circuitry.
To calibrate the thermocouple circuitry on the DT9805 or DT9806
modules, perform the following steps:
1. Disconnect all signals to Analog Input 0 (TB1), leaving it open (no
connections).
2. Connect Analog In 1 (TB3) to Analog In 1 Return (TB4) and to
Analog Ground (TB17).
3. In the PGL Zero box, click the text A/D Gain=500, CH 1 to refresh
the value of analog input channel 1.
The gain is set to 500 automatically.
4. Click the increment or decrement arrows in the PGL Zero box
until the A/D value reads 0 V (within 5 mV).
5. Measure the room temperature at the temperature sensor of the
board (see
Figure 15 ) by taping a thermometer to the underside
of the module between screw terminals 9 and 10, then multiply
this value by 10 mV.
This is the temperature that you want to adjust the CJC to.