Hioki IM3536, Instruction Manual

Page: 251 / 270

Appx.
11
Open Correction and Short Correction
Appx. 8 Open Correction and Short Correction
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 component, 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.
H
CUR
H
POT
Rs
L
POT
L
CUR
Ls
Zs
G
Co
Yo
Zm Zx
Fixture Measurement sample
Zx
: true value
Ls
: residual inductance
Co
: floating capacitance value
Yo
: open circuit residual component
Rs
: residual resistance
Go
: residual conductance
Zs
: short circuit residual component
Zm
: measured value
In this case, for the measured value
Zm
:
Zx
1
Yo
1
Zs Zm
+
+ =
The residual components can be determined in the following manner:
Open correction:
The terminals of the test fixture are left separated (open circuited). Because the short circuit residual compo -
nent
Zs
is now zero, therefore the open circuit residual component
Yo
can be determined.
Short correction:
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 compen -
sation process may then be performed by substituting them into the above equation.
The determination of test range is performed according to the measured value
Zm
for impedance. There -
fore it may happen that testing cannot be performed, when HOLD is on, if the test range is determined
merely according to the value of impedance of the sample under test. In this case, you should set the test
range in consideration both of the impedance of the test sample and also of the residual impedance compo -
nents of the test fixture.
Deviations in the measured values can become comparatively large in the following cases:
If only open correction has been performed.:
With open correcton only having been performed, since no correction 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.
If only short correction has been performed.:
With short correction only having been performed, since no correction 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.
Be sure to perform both types of correction to avoid this situation.
10
9
8
7
6
5
4
3
2
1
Appx.