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quite serious and may cause coma or death of the operator. Where permitted by the product, it is
recommended to turn on the ground wire current detection.
4.4.8 Current over limit and arc detection (ARC) function
Current over limit is divided as: current low limit, current high limit, current over limit and arc
detection.
Current low limit judge(LOW): generally for judging low terminal break. When instrument
tests device, there must be a certain leakage current, when the leakage current is smaller than
the set current value, it means fail, if the leakage current of DUT is quite small, then it is not
necessary to turn off the function. It displays (LOW FAIL) in over limit. This judgement is
valid only in the test mode and the timing sampling rate is 100mS/time.
Current high limit judge (HIGH): When instrument tests device, there must be a certain
leakage current, when the leakage current is larger than the set current value, it means fail. It
displays (HI FAIL) in over limit. The timing sampling rate is 100mS/time.
Current over limit: current sampling judge is slow and sometimes the current changes
quickly so that sampling circuit can’t reflect, otherwise, if current has passed the range of
current test, it would trigger the over limit judge. It displays (SHORT FAIL) in over limit.
Because the data can not be collected after the current is in over limit, the output result
is the test result before the current is in over limit. The current limit value is twice the
output current value allowed by the instrument (the relative AC is 1.5 times of the peak
value). When the fall time is invalid, this judgement is nonmaskable.
Arc detection (ARC): It is a practical function in coil component test, which tests the instant
fire in partial circuit of high voltage. Because the speed of partial fire is quite fast, and the
filter coefficient of common current detection circuit is so large that it can’t make a suitable
judge. Arc detection circuit filters out the normal current value and only deals with the
change of fast current pulse. This function can only roughly estimate the degree of partial
fire due to the randomness of lowpass filtering and arc. Because the data can not be
collected after the current is in over limit, the output result is the last test result when
the current is in PASS. It displays (ARC FAIL) in over limit.
Current over limit judge and frequency response contrast of arc detection: (in the figure above)
Zone A: Current sampling display circuit frequency response. Filtering out the power
ripple → AD sampling → computation of the test result→ analyzing whether the current
exceeds the limit setting. In the test current range, the pulse width is greater than 100mS.
Zone B: Current fast response circuit. This circuit only filters out high-frequency
interference signal → voltage peak contrast → over-flow peak signal lock, only deals
with limit judge. When the current is larger than the output current allowed by the
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