Fluke 2680A Service Manual page 144

268XA
Service Manual
4. Resolve any calibration problems based on the following:
5-14
channel 1 provides the full scale reading and measuring the four-wire short on
channels 2 and 12 determines the zero offset error. The four-wire ohms gain and
offset calibration constants are determined from these two measurements.
The 5700A provides a limited set of reference resistors where the best resistor for
each range is at 63.3% of full scale. This will give very good results, but making the
measurement closer to the full scale value using fixed resistors may give better
results. When you are using fixed resistors, you must use the CAL_REF command to
tell device the value of the new reference resistor. When you are using fixed resistors,
you connect the leads as they are for any four-wire ohms measurement.
An execution error !> is returned by the CAL_STEP? command if the full scale
measurement is off by more than 5% from the target or if the zero measurement
is off by more than 1% of full scale. 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.
If CAL_STEP? returns an execution error !> while measuring the four-wire short
on channels 2 and 12, the procedure freezes at the internal step that measures the
short. This way, you can send a CAL_REF? command and it will return 0 W,
indicating that the problem was probably caused by a misapplied short on
channels 2 and 12.
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 33% of full scale or greater than 100% of full scale for any
range.