Sect. D - Operation, Functional Self-Test and Use
By using a 4-wire Kelvin type lead set or by
shorting the
V
and
I
terminals together and
HI
HI
V
and
I
terminals together the instrument
low
low
is in the 2 wire resistance mode.
Resistance Offset in 2 Wire mode
All wiring including harness wires from the two
wire test connection out, that
are "
in series
"
with the test squib resistance
become part of the
actual two wire measurement (
another potential
source of measurement error if not
compensated for
) . Many Ordinance test
procedures have the 620 series Igniter Tester
user short their wiring harnesses at the very end
(by the squib) and record the resistance value or
offset. Then when the 620 series Igniter Tester
leads, including the in-series harness wiring
resistance, is connected to the test squib, the
squib test resistance can be calculated (via
subtraction of the 2 wire harness - test lead
resistance offset).
That is the 2 wire lead length shorted offset
resistance (without the squib resistance) can be
subtracted for the total resistance (including the
squib resistance) to determine the actual squib
(test) resistance.
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