45
Service Manual
4-18
Table 4-7. Calibration Using the Computer Interface (cont)
Continuity/Hysteresis Threshold Calibration
Step Apply input Wait for meter settling time Send
30
31
0.000 mV dc
20.00 mV dc
1 s
1 s
CALSTEP?
CALSTEP?
Frequency Calibration
32 10 kHz, 2.000 V p-p 2 s CALSTEP?
(xxxx... represents the known exact ohms value of the source)
* A 190 Ω source calibrates the 300 Ω range on the Fluke 45 to 0.06%+2 digits +0.02 Ω. For calibration of
this range to 0.05%+2 digits +0.02 Ω, use a 290 Ω source and the procedure detailed under Alternate
Ohms Calibration (Computer Interface). This procedure can also be used with appropriate discrete resistor
values (such as a decade box) on all ranges.
** Note that the 290 kΩ and 2.9 MΩ ranges are quite sensitive to noise. Any movement of the input leads
or movement of the hands or body in the vicinity of the leads can cause noisy readings. Use shielded
leads during this calibration. These two cal points should be verified for accuracy at the conclusion of
calibration.
4-22. The Calibration Procedure
Now select calibration mode on the Fluke 45. Using a thin, blunt-tipped object, press the
recessed Cal Enable button for three seconds. Avoid using sharp objects that might
damage this button. Refer to Table 4-8 for brief descriptions of calibration mode
commands.
The CALREF xxx.xx command tells the Fluke 45 to change the calibration prompt to the
exact value of the input from the calibrator. Use of this command is equivalent to the act
of editing the calibration prompt from the front panel when other than exact calibration
points are to be used.
The CALSTEP? command normally returns the calibrated value of the input. If the input
is not within an anticipated range of the expected value (5 to 15%, depending on the
step), a beep is sounded at the front panel, a device dependent error is returned over the
computer interface, and the measured reading is returned.
The response to CALSTEP? must be received before each new step can begin. With
some steps (such as step 31), a noticeable delay may be encountered.
Before beginning calibration, consider the functions that will be affected. AC volts, dc
amps, ac amps, and ohms are all influenced by dc volts calibration. If you calibrate dc
volts, you must re-calibrate these other functions. But, calibration of ac volts, dc amps,
ac amps, and/or ohms influences only the function being calibrated.
If you plan to include the ohms function in your calibration procedure, determine the
residual lead and source zero resistance before you place the meter in calibration mode.
Use the following procedure:
1. Send: OHMS; RANGE 1
2. Measure the residual lead and source zero resistance on the 300 Ω range by sending:
VAL?
3. Record the response. This value is used if you elect to perform the Alternate Ohms
Calibration.
4. Now continue on with the calibration procedures in the following paragraphs.
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