Fixture Compensation; Fixture Compensation - Voltech ATi User Manual

2.8 F
IXTURE
The AT's fixture compensation eliminates errors due to stray parasitic
components on the fixture board itself. These are usually a combination of
parallel capacitance between adjacent wires, sockets or pins, and series
resistance and inductance along the lengths of wires.
It is best to try fixture compensation when performing trial runs on the program,
as it is being developed, using the Editor. As a guide, if fixture compensation
changes the test results, then it should be applied whenever the program is
run in a production situation.
For optimum accuracy in production test, fixture compensation measurements
should be made:
1. Whenever the test fixture is changed.
2. At the beginning of each day or work period.
3. Whenever a new test program is loaded into the AT for execution
Performing compensation on a fixture consists of making TWO measurements.
Short-circuit (S/C) compensation will compensate for the effects of stray
connection lead resistance and inductance. Open circuit (O/C) compensation,
will compensate for the effects of stray lead capacitance. See also the
description of 4-terminal 'Kelvin' connections in the fixture section of this
manual for how to eradicate the effects of CONTACT impedance between the
test part and the fixture.
To Perform Fixture Compensation
Once a program is ready to run, you will have the option of pressing the
COMPENSATE softkey on the panel.
Press COMPENSATE and you will be given the option to perform S/C or O/C
compensation. BOTH types of compensation should be performed, one after
the other. The order in which S/C and O/C compensation is performed is
unimportant.
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