True-rms Thermal Multimeter
Performance Tests
9
Current Tests
For the current tests, make the connections shown in Figure 2.
1. Apply the input level for each step shown in Table 3.
2. Compare the indication on the Multimeter display with the display reading limits in Table 3.
3. If the display indication falls outside of the range shown in Table 3, calibration adjustment or repair is necessary.
See Calibration Adjustment on page 15.
Figure 2. Performance Test Connections for Simulated Current
Ice Buildup and Purge Procedure (4180, below Dew Point)
WCaution
For IR calibration with the Fluke 4180 IR Precision Calibrator, it is critical to assure that
the target is free of any ice or moisture. Ice or moisture on the target changes the target
emissivity and apparent temperature. If any ice or moisture (even though it is a slight
amount) is on the target, the display temperature accuracy is invalid. In addition, ice
buildup can damage the surface coating and cause the radiometric calibration to drift.
To avoid ice buildup, the 4180 has a cover with a purge inlet. Fluke recommends that the target cover be used at any
set-point below the dew point. Depending on the ambient humidity of the environment where the target is used, the
dew point can be as high as the ambient temperature of that environment.
Purge Procedure
The cover allows the target to be used at temperatures below the dew point. The target is less likely to form ice while
the target is covered. The target cover has a purge inlet to further prevent ice buildup.
To use the purge:
1. Connect a 6 mm (0.25 in) outside diameter tube to the purge inlet on the target cover.
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