17. O-ring Water Tight Seal -
18. Padlock Holes
19. AMPTEC 601ES DMM Test Leads
Underneath the
AMPTEC 601ES DMM main panel is a sponge
rubber o-ring. A second O-ring is located inside
the rim of the AMPTEC 601ES DMM lid. When
the lid is latched shut, the o-ring in the lid is
compressed and provides a dust tight and water
resistant seal.
- The AMPTEC 601ES
Explosive Safety DMM can be locked (i.e.
during transit) to help prevent tampering and
provide added security.
- All
AMPTEC series test lead and probe sets are a
minimum 48" length, dual banana termination at
the ohmmeter end (call the Sales Department at
AMPTEC RESEARCH for any custom require-
ment).
IGNITER TESTER
*
* contact resistance
*
COMPLIANCE
VOLTAGE
LIMITED
CONSTANT
CURRENT
SOURCE
LEAD RESISTANCE
LEAD RESISTANCE
D-4. 4-Wire Kelvin Resistance Measuremen
test lead wiring
resistance and
contact
resistance
t
The AMPTEC 601ES DMM can be a 2 wire
method resistance meter. With all 2 wire
resistance meters, all
test lead connection
is in series with the "resistance under
test" and as a result a resistance error or offset
may be generated. Fig. D-4 illustrates how the
4-wire principle is used to eliminate lead, wire
and contact resistances as potential error
sources. The internal failsafe constant current
source inherently overcomes all series resistance
(within compliance voltage limits) and delivers
a precise constant current. The compliance
voltage of the AMPTEC 601ES DMM constant
failsafe current source will drop as the
resistance under test increases to maintain
IGNITER TESTER KELVIN BLOCK DIAGRAM
FIG. D-4
constant current (i.e. 5 mA on the 2.0 ohm and
20 ohm ranges). The constant current may be
thought of as in a loop from
out to the
“UUT” and back to the AMPTEC 601ES DMM
through the
jack. Depending upon the
magnitude of the resistance offset, some of the
offset may be corrected (zero ed out) for in the
AMPTEC 601ES DMM by adjusting the zero
knob on the front panel. The four-terminal
configuration of the AMPTEC 601ES DMM
eliminates errors normally caused by in series
test lead resistance and contact resistance(s). In
many applications the contact resistance and can
exceed the value of the test resistance by several
orders of magnitude. The AMPTEC 601ES
DMM overcomes this potential error source by
providing two terminals of constant current and
an additional two terminals for high impedance
voltage measurement. 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 DC Digital Voltmeter
(DVM) senses the voltage drop across the test
resistance (i.e. igniter/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 (
and
) leads.
When in 4 Wire Kelvin (Ohms) mode, the four
terminals used are current high(
), current
low (
) as well as the voltage sense high
(
) and voltage sense low (
). The
unit’s top two
binding posts labeled
are
and
. The unit’s lower
two
binding posts labeled
are
and
Fig. D-5 illustrates 4 Wire Kelvin connections
from the unit’s binding posts to the resistance
under test. Gold plated 4 wire Kelvin Clip test
leads (Option 300) are normally supplied with
the AMPTEC 601ES DMM. The Kelvin Clips
I
I
V
V
D-5. Connections
I
I
V
V
+
High
V
I
Low
V
I
.
HIGH
LOW
’
hi
low
HIGH
LOW
HIGH
LOW
HIGH
HIGH
LOW
LOW
horizontal
horizontal
-
2 Wire
4 Wire
Resistance
under
test
+ HIGH
LOW
V
LO
LO
HI
HI
I
I
I
4 WIRE KELVIN OHM USES ALL 4 TERMINALS
FIG. D-5
Sect. D - Operation, Functional Self-Test and Use
14
