ST2683A Operation Manual Ver.1.3
19
Figure 3-4 Test connection program
NOTE:
There is voltage output in HV (-) terminal. Please connect the DUT in discharged condition.
Beware of electric shock. The device is not potential-free, so any voltage output from the
HV (-) terminal is relative to ground.
Only current flowing into the INPUT terminal is considered for calculating the impedance of
the DUT. This is to prevent stray capacitive charging current to ground from influencing the
measurement as these currents will be diverted to the GUARD terminal or another ground
connection. However, this will lead to wrong results when the DUT itself is not potential-free
and has a connection to ground somewhere, because the current will rather flow directly to
ground than through the internal resistor of the selected current range and then to ground,
resulting in a measured current that is too low and respectively a calculated resistance that is
too high. Thus, the measuring setup has to be designed in such a way that the impedance to
be tested has no connection to ground, so e.g. in an insulation resistance test, all parts that
are normally connected to ground have to be connected to INPUT instead.
Accordingly, if the monitored voltage breaks down even though there is no or only a small
current displayed, there is a low-impedance parasitic connection to ground somewhere.
DO NOT attempt to remove the device’s ground connection to try to make the device
potential-free and circumvent the above mentioned restrictions, as this can lead to the
device’s case and exposed metal parts being charged to dangerous voltage.
Be sure to connect DUTs with polarity (electrolytic capacitor, etc.) according to the positive
and negative terminals shown in the diagram, otherwise it may result in the explosion of
components. Take it down after discharging for a few seconds to prevent electric shock.
Short circuit of the instrument for a long time is not allowed; otherwise it will damage the
instrument.
In order to obtain ideal accuracy and stability, the test environment must first be guaranteed
to be according to the conditions described in the Chapter One---“Environment”.
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