Specifications

A-5
A.3.3 Test fixture’s adaptability for a particular measurement
In order to make use of what has been discussed previously, the test fixture’s adaptability for a par-
ticular measurement will be discussed. To see whether a test fixture is adaptable, it is important to
think about the test fixture’s additional error (proportional error, short repeatability, and open
repeatability), measurement impedance, and the test frequency range.
If the measurement impedance is in the 1 Ω to 10 kΩ range, use only proportional error to calculate
the additional error of the test fixture. It is fine to assume that this is a close approximation to the
fixture’s additional error.
If the measurement impedance is not in this range, use proportional error, short repeatability, and
open repeatability to calculate the test fixture’s additional error. Recent test fixtures have all three
terms specified in their operation manual, so use these values for the calculation.
Some of the recent test fixtures (16044A), due to their structure, have different performance charac-
teristics with different measurement instruments. For these test fixtures, refer to their operation
manual for more details about the specifications.
If the test fixture is not specified with short and open repeatability, how can the fixture’s adaptability
be determined? To measure a test fixture’s short repeatability, measure the impedance of the short
condition after performing short compensation. Take the shorting plate out of the fixture and then
replace it. Measure the short condition again. By repeating this process at least 50 times, it will show
the variations in the measured impedance of short condition (see Figure A-6.) The final step to
determine an approximation of short repeatability is to add a margin to the values obtained. For
open repeatability, measure the admittance of the test fixture’s open condition. In the same way,
determine open repeatability by measuring at least 50 times.
Figure A-6. Measurement of short repeatability (16034G)
Specifications of
short repeatability
Actual measurement
of short repeatability