Omega CL24, CL25, CL27, CL23A, CL26 manual Resistance Calibration, Test Equipment Required

B. RESISTANCE CALIBRATION

NOTE: Thermocouple and resistance calibrations are indepen- dent. However, potentiometer P1 is used in both thermocouple and resistance calibrations to set EEPROM constants. Follow cal- ibration procedures carefully to ensure that thermocouple and resistance calibrations do not disturb one another.

Test Equipment Required:

1.Resistance Decades (General Resistance RTD-100, RTD-500/1000, and RDS-54, or equivalent).

2.Current Source (Fluke 5101B, or equivalent).

3.Digital Multimeter (OMEGA OM7551, or equivalent).

4.Calibration cables per Figure 14.

Ambient Conditions:

Unit should be calibrated at an ambient temperature of 23°C±1°C, with rela- tive humidity less than 80%.

Preparation For Calibration:

1.Turn off unit, and remove bottom-cover. Refer to Disassembly Instructions.

2.Secure battery with a piece of adhesive tape.

NOTE: Momentary loss of battery power during the following cal- ibration will invalidate previous adjustments, both resistance and thermocouple.

3.Hook up test-equipment and unit per Figure 14.

4.Set current-source to 1mA, STANDBY mode.

5.Set DMM to 2V DC range.

6.Turn on unit.

7.Set unit to METER mode, RTD-100, °F.

8.Turn off unit. Remove jumper J1. Turn on unit. 'RTD' annunciator should be flashing.

NOTES: Flashing 'RTD' indicates that calibration adjustments will be written to memory. Avoid selecting thermocouple functions while in this mode.

NOTES: Should it be necessary to scroll through thermocouple functions, first hit the OPR key (disables flashing 'RTD'), and start again at Step 7 above.

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