Extech Instruments EX840A Quick Start Manual page 6

Low Pass Filter (LPF)
To introduce a low pass filter when measuring AC voltage, long
press the LPF button. Long press again to exit. Use this feature
when measuring variable frequency drive (VFD) equipment.
Low Impedance Mode (LoZ)
If ghost voltages are a concern, select the LoZ switch position
when measuring voltage, to lower the input impedance to approxi-
mately 3 kΩ.
DC Current Zero (Offset)
In DC current mode (with no conductor in the jaw), long press the
ZERO button until the beeper sounds. The display will zero. The off-
set value is now stored and removed from subsequent measure-
ments. Long press ZERO to exit.
Inrush AC Current
Capture inrush when measuring AC current. Long press the IN-
RUSH button with the circuit under test unpowered, INRUSH will
appear on the display. Switch power on to the circuit under test and
view the inrush current on the display. Long press INRUSH to exit.
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