5520A
Service Manual
3-10
3-8. Thermocouple Function Calibration
The equipment listed in Table 3-6 is required for calibration of the thermocouple measure
and source functions. (The equipment is also listed in the consolidated table, Table 3-1.)
Table 3-6. Test Equipment Required for Calibrating the Thermocouple Function
Quan. Manufacturer Model Equipment
1 Fluke 5520A/LEADS Test lead set (includes Type-J thermocouple,
wire, and mini plug)
4 feet various various 24-gauge solid copper telephone wire
1 ASTM 56C Mercury thermometer
1 various various Dewar flask and cap, mineral oil lag bath
1 Hewlett Packard 3458A with -002 option DMM
Proceed as follows to calibrate the thermocouple function:
1. Verify that the UUT is in standby.
2. With nothing connected to the UUT terminals, press the GO ON softkey as prompted
to start TC calibration. Wait for the internal calibration steps to complete.
3. Connect the HP3458A DMM to the TC terminals using solid copper telephone wire
and a copper (uncompensated) TC miniplug as shown in Figure 3-4. Attach the wires
directly to the DMM binding posts. Set the DMM to read dc millivolts.
4. Enter the measured value into the UUT for step 1 in Table 3-7 as prompted.
5. Disconnect the test equipment.
6. Connect a Type-J thermocouple to the TC terminals on the UUT, and immerse the
thermocouple and a precision mercury thermometer in a mineral oil lag bath that is
within ±2 °C of ambient temperature. The test setup is shown in Figure 3-5.
7. Wait at least 3 minutes for the temperature readings to stabilize, then read the
temperature on the mercury thermometer and enter it into the UUT.
Table 3-7. Calibration Steps for Thermocouple Measurement
Step 5520A Output (AUX HI, LO)
1 300 mV dc (NORMAL)
2 Enter temperature read from mercury thermometer as prompted
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