Hioki IM3570 - Appendix 9 Open Circuit Compensation and Short Circuit Compensation

Appendix
Appendix 9 Open Circuit Compensation and Short Circuit Compensation
A13
The residual impedance component of the test fixture can be considered in terms of an equivalent circuit as
shown in the figure. Further, because the measured value
Zm for impedance includes this residual compo-
nent, therefore, in order to obtain the genuine impedance value, it is necessary to compensate the measured
value in terms of the open circuit impedance residual component and the short circuit residual component,
which accordingly must be obtained.
Zx: true value Rs: residual resistance
Ls: residual inductance Go: residual conductance
Co: floating capacitance value Zs: short circuit residual component
Yo: open circuit residual component Zm: measured value
In this case, for the measured value Zm:
The residual components can be determined in the following manner:
• Open circuit compensation
The terminals of the test fixture are left separated (open circuited). Because the short circuit residual com-
ponent
Zs is now zero, therefore the open circuit residual component Yo can be determined.
• Short circuit compensation
The terminals of the test fixture are connected together (short circuited).
Because the open circuit residual component
Yo is now zero, therefore the short circuit residual component
Zs can be determined.
These residual components thus obtained are recorded as compensation values, and the compensation pro-
cess may then be performed by substituting them into the above equation.
Deviations in the measured values can become comparatively large in the following cases:
• If only short circuit compensation has been performed.
With short circuit compensation only having been performed, since no compensation can be performed in
terms of the open circuit residual component
Yo (which is not available), thereby deviation in the resultant
values will become large if the value of that open circuit residual component
Yo is relatively large.
• If only open circuit compensation has been performed.
With open circuit compensation only having been performed, since no compensation can be performed in
terms of the short circuit residual component
Zs (which is not available), thereby deviation in the resultant
values will become large if the value of that short circuit residual component
Zs is relatively large.
In order to avoid this sort of thing, be sure always to perform both short circuit compensation and also open
circuit compensation.
Appendix 9 Open Circuit Compensation and
Short Circuit Compensation
Zs
Rs Ls
Go Co
Yo
Zx
Test sample
Test fixture
Zm
H
CUR
H
POT
L
POT
L
CUR
Zm Zs
1
Yo
1
Zx
------+
--------------------
+=
The determination of test range is performed according to the measured value Zm for impedance. Therefore it
may happen that testing cannot be performed, when HOLD is on, if the test range is determined merely accord-
ing to the value of impedance of the sample under test. In this case, you should set the test range in consider-
ation both of the impedance of the test sample and also of the residual impedance components of the test
fixture.