Extech Instruments MA440 User Manual page 16

Non‐Contact Voltage‐Detector (EF/NCV)
The area at the top of the clamp jaws is used for sensing AC voltage or an electromagnetic field.
For the MA400, when the electrical field is > 100V and the distance is < 10mm, the beeper will
sound and the red LED lamp will light.
For the MA443 and MA445 when the electrical field is >100 V and the distance is < 10mm, the
LCD will display dashes, the meter will beep, and the red LED lamp will light.
The NCV lamp flashes at the same rate as the beeper. The
higher the field strength, the greater the number of dashes
displayed (up to 5) and the faster the beep rate and lamp
flashing.
When the sensed field is at highest levels, the meter's NCV
lamp and beeper rate will become as one continuous light and
tone.
If the meter does not react as described above to an AC
voltage or electromagnetic field, there is still the possibility
that a voltage or field is present. Please use caution.
1. Move the function switch to the NCV position.
2. In this mode, the MA443 and MA445 meter will display
'EF' (electromotive force) and the MA440 will displays
'OL'. These indicate that the meter is in the NCV mode
but is not sensing an AC Voltage or an electromagnetic
field.
3. Place the meter near a source of electrical energy. The tip
of the clamp offers the highest sensitivity.
4. Note the beeping, NCV lamp activation, and the dashes
(MA443/MA445) when an AC Voltage or electromagnetic
field is sensed.
Fig. 12 – Non‐Contact Voltage Detection
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