Differences between 780, 785, & 790
Model 780, 785, and 790 holiday detectors incorporate new
circuitry allowing the detectors to maintain a selected voltage,
regardless of different pipe diameters, coating thickness variations
and battery wear (unless the battery is totally discharged). Keep in
mind that the voltage the coating actually “sees” will decrease
slightly depending on ground losses and/or conditions.
The model 780 holiday detector is a low voltage (1-5kv) detector
designed specifically for thin film epoxy coating.sThe output voltage of
this detector is normally D.C. (direct current). However, if moisture is
encountered on the pipe, the detector output automatically switches
to a fast pulse. Fast pulse enables continued operation whereas
with older type thin film detectors the operator either had to wait until
the moisture evaporated or the pipe had to be dried.
The model 785 holiday detector is a high voltage (1-15kv)
detector designed to cover a wide range of coatings from thin films to
tapes to extruded or coal tar types of coatings. Since the operating
characteris- tics of this detector are very broad it is recommended
that thin film epoxy coatings be inspected with the model 780
detector.
The model 790 holiday detector is a high voltage (5-35kv)
detector designed specifically for tapes, extruded or coal tar types of
coatings, and thicker somatic type coatings.
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