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probe, and DUT are charged to a high voltage. The tester is equipped with a discharge circuit, but some
time is nonetheless required to discharge them after the output is cut off. There is a danger of electric shock
during discharge. To avoid electric shock, take the utmost care to ensure that the DUT, test lead wire,
probe, and highly charged parts around the output terminal are not touched. If it is necessary to touch them,
be sure to confirm the DANGER lamp has gone out.
As soon as the output is cut off, the tester’s discharge circuit starts forced discharging. Do not disconnect
the DUT during a test or prior to completion of discharging.
Under normal circumstances, it can be guaranteed that the test loop voltage is within the safe voltage range
when finishing discharging. When the capacitance of the DUT is too large or the structure of the DUT is
special, it may leads to incomplete discharge. In order to ensure complete discharge, test method must be
changed by technical personnel.
Discharge time:
Computational formula of discharge time: t = -ln（30 / U）×R×C
t: discharge time
30: discharge residue safty voltage 30V
U: test set voltage
R: discharge impedance of the DUT, the discharge impedance of the instrument is approx. 10k
C: capacitance of the DUT
In general, only DC high voltage test needs discharge and the length of the discharge time varies according
to the properties of the DUT.
If the test terminated normally, the voltage will drop to zero according to the voltage fall time. If the test
failed, discharge of the DUT is conducted by the transformer secondary winding (resistance of
approximately 10k). Approximately 0.05s are required for 1uF capacitor with high voltage of 6000V to
discharge to 30V. The fixed discharge time of the instrument is 0.2s, which ensures complete discharge of
the device.
2.5 Dangerous States of Failed Tester
Typical possible dangerous states of the tester are as shown below and in which cases the most dangerous
situation that “the high test voltage remains delivered and the instrument get out of control” may
occur. When this situation has occurred,
1. Immediately turn OFF the power switch and disconnect the AC power cable from the AC line
receptacle.
2. Immediately keep far away from the instrument and confirm no risk of the test circuit by the technical
personnel; or keep the instrument still for more than one hour and confirm no output voltage in the test
terminal.
3. Remove the relevant connecting lines and send the instrument back to us for maintenance.
WARNING: Keep away from the instrument after turning off the power and prevent other people from
approaching. Do not immediately disassemble the test circuit. Immediately call our distributor or agent.
High voltage may remain in the interior of the instrument. It is hazardous for an unqualified person to
attempt to troubleshoot any tester problem.
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