Fluke NetDAQ 2640A, Service Manual

Page: 163 / 260

Performance Testing and Calibration
Calibration
4
4-41
Manual Frequency Calibration Procedure 4-46.
The Frequency calibration procedure calculates a calibration constant that corrects for
errors in the frequency counter crystal frequency. It is sufficiently accurate to measure a
single frequency point and calculate the scale factor assuming that the other endpoint is
0 Hz.
Complete the following procedure to manually calibrate the frequency function.
1. If you have not already done so, complete the procedure “Preparing for Calibration”
earlier in this chapter.
2. Connect the instrument and 5700A Calibrator as shown in Figure 4-7.
3. Complete the sequence of manual steps shown in Table 4-8. Channels 1 is
configured to frequency, and a single measurement is made.
Table 4-8. Manual Frequency Calibration
Command Response Action
CAL 4 => Puts NetDAQ in frequency calibration.
CAL_REF? +10.0000E+3 5700A - Source 3V ac @ 10 kHz
CAL_STEP? +10.0000E+3 NetDAQ computes the calibration constant
and returns the calibrated reading. Allow
several seconds.
4. Resolve any calibration problems based on the following:
•
An execution error !> is returned by the CAL_STEP? command if the frequency
measurement is off by more than 5% from the target. When an error is detected,
the cal constant is not updated, and the procedure remains at the same step.
•
When CAL_STEP? reports an execution error !> due to an out-of-range
measurement, it returns the raw measured reading to give you an indication of
what was measured. When CAL_STEP? completes successfully, it returns the
reference value.
•
A device-dependent error is returned by the CAL_STEP? command if an internal
error such as a measurement timeout is detected. When an error is detected, the
cal constant is not updated, and the procedure remains at the same step.
•
An execution error !> is returned by the CAL_REF command if the specified
reference is less than 10 kHz or greater than 100 kHz.