D-7.
Failsafe Operation
D-8.
Battery Monitoring Circuitry
The AMPTEC 640 Series of Igniter Testers or
failsafe ohmmeters incorporate a constant
current source design that renders them
incapable of delivering excessive voltage or
current to the device under test. The typical
fail-safe current for each range is indicated
under the corresponding range switch on the
640 series meter front panel. Please refer to
section E-6 for a technical description of the
failsafe circuitry specifics.
As a further precaution the 640 Series Igniter
Tester is isolated from the AC line whenever the
POWER switch is in the ON position.
The 640 series igniter tester receives its power
from an internal rechargeable battery pack (4
“D” Cell Ni-Cad batteries). The 640 series
igniter tester main power switch (see item 21
of the 640series igniter tester Front Panel
Diagram) must be in the OFF/CHARGING
position in order to charge the batteries. Of
course, the battery charger must also be plugged
into the unit’s keyed single access connector. As
mentioned earlier, the 640 tester’s notched
single access front panel connector allows
the slim-line battery charger to be connected or
the test leads to be connected to the 640 tester
but
. This “notched single access front
panel connector” safety feature helps eliminate
virtually any possibility of the operator
measuring with the 640 series igniter tester test
leads while also connected to an AC line
powered battery charger.
The 640 series igniter tester display has a ±
polarity display indicator preceding the unit’s
regular 4 ½ digit numeric display. The negative
polarity display LED (see item 6 of the 640
series igniter tester Front Panel Diagram) is
used as a Low Battery indicator.
If the low battery LED is illuminated, 640
Series Igniter Tester readings should not be
trusted. An overnight recharge should be
performed before using the 640 series igniter
tester for critical testing.
either
not both
Notice for Cal Lab:
remove the fuse
MAIN
The variable potentiometer
- RV3 is factory adjusted to have the low battery
indicator come on at 4.60 VDC. To make this
adjustment, and
from the
fuseholder. With an adjustable DC power
supply, set the power supply output to be 4.60
VDC. Be sure to observe power supply polarity.
Connect the power supply to the test points
labeled “
” + pos. and - neg. located in
the rear section of the 620A MAIN PCB. (i.e
po power supply output to the anode
side). Adjust trimpot RV3 to have the low
battery indicator just come on (negative sign on
display). An increase in power supply voltage to
4.62 VDC should have the low battery indicator
go out. Finally, disconnect the power supply,
and return the fuse to the fuse holder in the rear
panel.
Summary of Contents for 640N
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