640 Series Igniter Tester Front Panel Diagram
shown earlier).
The Single Access Multipurpose Notched Main
Connector is for either test lead hookup or
connection to the battery charger but not both at
the same time. With only one connector to the
outside world, it is physically impossible to do
both at the same time (charge and measure). The
power switch (item #21) must also be in the
“Off/Charging” mode while the battery charger
is connected in order to recharge the batteries.
The charging requirements supplied to the
internal battery pack are internally stepped
down from the 9VDC @1.1A supplied by the
charger. The correct charging voltage is supplied
by the adapter included with the instrument.
Additional AC/DC Battery Chargers are
available as Option "640DC". Typically an
overnight charge (16 hours) will provide about
an 6 to 8 hour continuous powered up life for
the 640N. The 640N has an internal ovenized
voltage reference the draws a considerable
amount of battery power when first turned on. If
you know you will be using the 640N again in
10 to 15 minutes, you actually
power
.
The four-terminal configuration of the 640N
eliminates errors normally caused by in series
test lead resistance and contact resistances. In
many applications the contact resistance and can
exceed the value of the test resistance by several
orders of magnitude. The 640N overcomes this
potential error source by providing two
terminals of constant current and an additional
two terminals for high impedance voltage
measurement. The result is a fast, accurate
conserve battery
by not turning it off
D-5. 4-Wire Resistance Measurement
resistance measurement of the test resistance,
independent of the resistance of the current
carrying leads.
Figure D-1 illustrates how the 4-wire principle
is used to eliminate lead, wire and contact
resistances as potential error sources. The
internal constant current source inherently
overcomes all series resistance (within
compliance voltage limits) and delivers a
precise constant current. Separate DC to DC
isolation circuitry provides independent circuit
voltage supplies for both the constant current
source circuit and the voltmeter circuit. The
internal high-impedance Digital Voltmeter
(DVM) senses the voltage drop across the test
resistance (i.e. squib or detonator). There is
negligible contact and lead resistance error
created by the voltage measurement because the
high input impedance of the DVM limits
current flow in the voltage (V and V
) leads.
Connections are made to the front panel
terminals using a 4-wire configuration as
described in section D-5. Only use AMPTEC
test leads supplied with the 640N Failsafe
Ohmmeter. When using AMPTEC test leads,
the notched connector end plugs directly into
the single access notched main connector (see
J1 manual section E-6) of the 640N. Next turn
the connector clockwise until you feel the notch
or click of the mating connector of the 640N.
All AMPTEC 640N leads have the 4 wire
current high, current low as well as the voltage
sense high and voltage sense low routed to the
end of the leads. The 4 wire Kelvin wires then
terminate in a pair of single banana plugs. One
banana plug (red) for current and voltage high,
and another banana plug (black) for current and
voltage low.
The 640N’s keyed single access connector also
make it extremely difficult if not virtually
impossible during normal operation to mis-
connect measurement leads to the 640N .
For 640N leads other than those terminated with
banana plugs, RG-58 Shielded Coax Cabling is
used. Maintaining the four wire Kelvin measur-
ment, the current is in the largest conductor and
the voltage input is shielded.
I
hi
low
D-6.
Connections
IGNITER TESTER
Figure D1 - Igniter Tester Kelvin Block Diagram
*
* contact resistance
*
COMPLIANCE
VOLTAGE
LIMITED
CONSTANT
CURRENT
SOURCE
LEAD RESISTANCE
LEAD RESISTANCE
Summary of Contents for 640N
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