Hioki DSM-8542, Instruction Manual, Page: 69 / 140

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The equivalent circuit shows that Current i
1
flowing through the sample and current i
2
that
flows through Insulating Materials a and b both flow to the input circuit through the
Terminal B.
Next, using a meal plate for example as the holder plate of the holder and connecting it
to the “GUARD” terminal of the meter, the current flowing to the “INPUT” terminal will be
only the current that flows through the sample after the current that flows through
Insulating Materials a and b is eliminated. The equivalent circuit in this case is the
circuit in Fig. 6.2(b) with a guard.
This equivalent circuit shows that Current i
2
that has passed through Insulating Materials
a flows directly to the common side of the current measuring unit without entering the
input circuit, to which only Current i
1
that has passed through the sample is input.
Generally speaking, a guard is provided to a jig or a holder by connecting this guard
circuit to the “GUARD” terminal of the meter by making all currents that are not measured
to flow a guard circuit.
6.2.2 Auto measurement
Auto measurement, in which a jig or a terminal to be measured is automatically changed,
facilitates measurement when there are many parts to be measured or there are many
points of measurement.
When measuring samples by changing samples, jigs or terminals to be measured, a
change must be must be made tuned to timing of meter operation by the following two
methods.
(a) Change the sample or the jig tuned to the “/INDEX” signal output from the
“HANDLER” connector on the rear panel of the meter.
In this event, the meter should be set to the Internal Trigger mode or Manual Trigger
mode and measurement is started by the Internal Trigger mode or Manual Trigger.
In the Internal Trigger mode, averaging setting to average measured results can be
set.
(b) Output a trigger pulse on timing to change a sample and input the pulse to the “EXT
TRIGGER” connector or the “HANDLER” connector on the rear panel of the meter.
In this event, the meter should be set to the External Trigger mode and
measurement is started tuned to a trigger pulse that is input to the “EXT TRIGGER”
connector or the “HANDLER” connector on the rear panel of the meter.
Note:
See 9. “External Interfaces” for more information on output of a synchronous pulse and
input of an external trigger pulse.
See 5.2.7 “Setting averaging function” and 5.2.8 “Setting trigger mode” for setting of the
averaging function and trigger mode respectively.
[Notice]
The [START] key outputs measuring voltage to ready a trigger. Pressing the
[START] key while the trigger mode is “INT” starts measurement. Note that
measurement is started by the [MAN. T] key or trigger input to “EXT TRIGGER”
input when the trigger mode is “MAN” or “EXT.”