error or offset, if not compensated for. The front panel “ZERO” knob allows the AMPTEC 620UK Safety
Ohmmeter user to
zero out
most typical test lead resistance.
That is -
T
or measurements above 2.0 K Ohms and higher, the “zero knob” adjustment isn’t needed and has no effect (as
the level of test lead resistance offset is so very small compared to the higher resistance level of the “resistance
under test”) .
The steps to adjust the “ZERO” knob (up to 10 turns) are as follows: ( disregard for V4 Version)
he zero knob is for “zeroing or nulling
out” the typical 100-150 milliohms worth of test lead wiring resistance and contact resistance offset - which is
determined when the leads are shorted (
see below
).
F
Repeat
: The front panel “zero knob” doesn’t have an effect on the unit’s 2.0K Ohm or higher
ranges
.
1.
Select the 2.0 Ohm range (
by rotating the unit’s range selection switch to the 2.0 Ohm position
).
2.
With the NATO pattern 104 compatible test leads connected to the AMPTEC 620UK Ohmmeter,
connect or
short the leads at the end together .
For example - if they are alligator clip (option 620UK-290) or banana jack
ends (option 620UK-401), connect or short the ends to each other.
3.
Adjust the ten turn ( precision potentiometer) zero knob until the AMPTEC 620UK Ohmmeter LCD display
indicates a reading of all zeros (
0000
). Turning the front panel “
zero knob
” a counter clock-wise direction
compensates by decreasing the resistance offset of the test leads. Turning the zero knob a clock-wise direction
compensates in by increasing (more or higher) resistance offset.
If you over-adjust the zero, beyond all zeros
on the display, the negative polarity sign comes on the display
indicating a condition of “
over-adjustment
”.
Simply turn the knob in the clock-wise direction (pos +) until the negative sign in the display disappears . Once
the “ZERO” adjustment of the test leads is accomplished, the AMPTEC 620UK Ohmmeter test leads are ready
to connect to the resistance under test. Once the user has zero’ed the unit’s 2.0 Ohm range, re-zeroing the
AMPTEC 620UK’s other ranges isn’t normally necessary.
AMPTEC 620UK
Explosive Safety /
Ohmmeter
Test Lead Length Resistance
Contact Resistance
Shorted Test Leads
V
HI
I
HI
V
LOW
I
LOW
12
