Specifications

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 focused upon. To see whether a test fixture is adaptable, it is important

to think about the test fixture’s additional error (proportional error, short and open repeatability),

measurement impedance and the test frequency range.

If the measurement impedance is in the 1 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 fix-

ture’s additional error.

If the measurement impedance is not in this range, use proportional error, short and open offset

errors to calculate the test fixture’s additional error. Recent test fixtures have all three terms speci-

fied in their operational manual, so use these values for the calculation.

Some of the recent test fixtures (e.g. 16044A), due to their structure, have different performance

characteristics with different measurement instruments. For these test fixtures refer to their opera-

tional manual for more details about the specifications.

So, how are test fixtures, which are not specified with short and open repeatability, assessed whether

they are adaptable or not? This assessment is made possible by using the following method to

approximate short and open repeatability. 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 insert it back in. Measure the short condition again. By repeating this

process at least 50 times, it will show the variations in the short condition (See figure below). 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.

Measurement of short repeatability (16034G)

Specifications of

Short Repeatability

Actual Measurement

of Short Repeatability