Appx.
4
Measurement of In-circuit Components
Appx. 3 Measurement of In-circuit Components
Measure an in-circuit component after providing
guarding.
4
3
2
4
3
2
R
R
R
R
R
R
R
+
+
+
•
=
Referring to the following figure, when measuring a resistance
value for the resistor
R
2
, even if the tips of the two probes are
contacted against the ends of the resistor
R
2
, considering the
sum of the current flowing through the resistor
R
2
and the cur-
rent flowing through the resistors
R
3
and
R
4
what is obtained is
the resistance value for the parallel combination:
R
1
R
2
R
3
R
4
H
L
If as shown in the next figure a guard terminal is used, the cur
-
rent flowing through the resistors
R
3
(not flowing through
R
4
) is
absorbed by this guard terminal, so that the resistance value
for the resistor
R
2
is accurately measured.
R
1
R
2
R
3
R
4
H
L
Guard terminal
•
The accuracy of measurement will not be improved in cases where for example
R
2
>>
R
3
and
R
3
is close to
zero.
•
As shown in the figure below, it is not possible to use this type of separation process for testing of the im
-
pedance values of two resistors or other elements of identical types which are connected in parallel, or for
testing of the impedance values of a coil and a capacitor which are connected in parallel.
Two resistors in parallel
Coil and capacitor in parallel
Summary of Contents for IM3536
Page 20: ...16 Operating Precautions ...
Page 34: ...30 Screen Layout and Operation ...
Page 140: ...136 Testing the System Self diagnosis ...
Page 224: ...220 About Measurement Times and Measurement Speed ...
Page 240: ...236 Discarding the Instrument ...