Testing Cjc (Cold Junction Compensation); Cjc (Cold Junction Compensation) Calibration - Fluke 525A Service Manual

Testing CJC (Cold Junction Compensation)

Connect a Type-J thermocouple to the TC terminal on the 525A. Immerse the
thermocouple and a precision thermometer into a mineral oil lag bath. The test set-up is
shown in Figure 9.
Verify that the readings of the 525A and the precision thermometer are within the Type-J
specifications:
• The 90 day spec is 0.14 °C
• The 1 year spec is 0.16 °C
Typical Type-J thermocouples Do not have specifications accurate enough
to be used as a standard. To maintain a good Test Uncertainty Ratio (TUR)
a characterized Type-J thermocouple may need to be used.

CJC (Cold Junction Compensation) Calibration

Connect a Type-J thermocouple to the TC terminals on the Calibrator, and immerse the
thermocouple and a precision thermometer in a mineral oil lag bath. The test setup is
shown in Figure 9. Verify that the readings of the thermometer and the Calibrator are
within the thermocouple specifications listed in the Specifications section.
525A TEMPERATURE / PRESSURE CALIBRATOR
VOLTS mA RTD
100mA MAX
HI HI
OUTPUT
100V MAX
TC
LO LO
INPUT/OUTPUT
20V PK
MAX
4W RTD
HI
20V PK
MAX
INPUT SENSE
LO
20V PK
MAX
J type
Thermocouple
Note
525A
STBY VOLTS TC TYPE
OPR mA RTD UNITS
OUTPUT INPUT ZERO
8 9
7 SHIFT
SETUP CJC C / F
4 5 6
SET RECALL AUTOSET
1 2 3
RNG LOCK LOCAL EXP
/ 0 •
ENTER CE
Figure 9. Connections for CJC Calibration
Mineral Oil
Lag Bath
Performance Tests
Mercury
Thermometer
Dewar Flask
and Cap
ajr22f.eps
525A
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