In addition, the 640 series Igniter Tester notched
test lead connector plug (640-plug) is optionally
available for customized wiring connections ,
kelvin clips, cables terminated with spade lugs,
and special banana jacks.
All AMPTEC ohmmeters use a high impedance
voltmeter as part of the resistance measurement
process. This voltmeter is a highly accurate and
stable 4½ digit analog-to-digital converter (A to
D). The High Impedance DVM must receive a
voltage input signal or drop in order to display
the proper value. When the DVM is not
receiving a definite input signal, the output
reading from the Analog to Digital Convertor
can appear random and wandering. The display
may indicate a randomly wandering number or
it may indicate an overrange (flashing)
condition. This unpredictable display (No input
to the DVM) condition may make it seem to
appear that the instrument is experiencing some
sort of malfunction. It is not a malfunction, in
fact, just a characteristic of the high impedance
voltmeter circuit and
- As this condition is
simply a state of an “open circuit” or “nothing
connected” to the DVM circuitry.
A flashing display (on and off usually all zeros)
indicates an over-range condition whenever the
terminals are open, or the resistance under test is
a higher value than the selected 640 Igniter
Tester resistance range. By using a 4-wire
Kelvin type lead set or by shorting the V and
I terminals together and Vlow and Ilow
terminals together the instrument is in the 2 wire
resistance mode.
All wiring including harness wires from the two
wire test connection out - are in series with the
test squib resistance and become part of the
actual two wire measurement (another potential
source of measurement error if not compensated
for) . Many Ordnance test procedures have the
640 series igniter tester user short their wiring
harnesses at the very end (by the squib) and
record the resistance value or offset. When the
640 Igniter Tester leads, including the in-series
harness wiring resistance, are connected to the
test squib, the squib test resistance can be
calculated (via subtraction of the 2 wire harness
offset).
should not be mistaken for
a fault in the instrument
HI
HI
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.
The display should indicate a stable reading
when the test leads are securely attached to the
device under test. If the display appears to be
erroneous when connected to the resistance
under test, recheck the test leads for integrity
and cleanliness. If all external items appear to
be functioning properly, the next step in
troubleshooting is to use the Function Test
Section of the AMPTEC 640 series igniter
tester. The Functional Test section contains test
resistors of known value. If a measurement
problem appears on the 20 Ohm range of the
meter, test for a zero offset problem first. Plug
the test leads into the 0.10 test resistor banana
panel jack built into the Functional Test Section
of the meter. If the meter displays a value close
to 0.1 Ohms then a resistance offset problem is
external to the 640N. The Cal Lab can adjust
the zero offset if the problem is with the 640N.
Two wire
offsets can be measured,
recorded (by measuring the shorted resistance)
and compensated for as part of a test procedure .
The 10.0 Ohm test resistor is also located
Functional Test Section of the meter. The 10.0
Ohm test resistor can be used for testing mid-
scale functionality of the 20 Ohm range.
Performing a similar Functional Test with the
meter across the 10.0 Ohm test resistor should
get a reading close to 10.0 Ohms (i.e 9.995
Ohms is OK). If the 640 Series Igniter Tester
appears OK after checking the test resistors in
the Functional Test Section then the connect-
ion problem must be outside of the 640 series
meter (i.e your wiring harness or the actual
device under test connection.) If the 640 series
meter doesn’t agree with the test resistors in the
Functional Test Section, then the meter or it’s
test leads are most likely broken. If this case,
please contact your local AMPTEC
RESEARCH Service Office, or call 1-800-350-
5105 or (512) 301-9333 (International
Overseas) or FAX (512) 301-9303, email
harness
Содержание 640N
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