Manual

96 • Calibration
11. Send “Span Calibration $(Addr)0” to analog input module five
times. (Actually, the address now is “00”, so the command is
“$001”).
*The apply source must be a precision source. The error
range in ±50uV is best.
CJC Calibration Procedure
1. Power off the module.
2. Connect the default pin to GND.(Because the calibration
procedures must be run under default mode).
3. Power on the module and find the module.
4. Ensure that the NuDAM units has been powered up for at least 30
minutes and is located away from sources of heat, in still air at
constant temperature.
5. Place a calibrated temperature meter, with a resolution of 0.1°C, in
close proximity to the CJC sensor of the NuDAM module.
6. Send command “Read CJC Status $(Addr)3” to read temperature
of CJC, then compare the temperature returned from the CJC
sensor with the calibrated temperature. (Actually, the address now
is “00”, so the command is “$003”).
7. If the difference is less than ±0.1°C, the CJC offset is correctly
calibrated, if it is greater or less, proceed to step 8.
8. Send “CJC Offset Calibration $(Addr)9(+0000)” to set initial CJC
offset value to zero.
9. Repeat step 6, then proceed to step 10.
10. Send “CJC Offset Calibration $(Addr)9(Counts)” to correct the
CJC offset error.(counts is a 4-characters with a sign + or -,range is
0000 to FFFF, each count equals approximately 0.0153 °C). (For
more detail, please refer the CJC Offset Calibration Command).
11. Repeat procedure 7 to procedure 10 if the CJC value still does not
conform to the ambient temperature.