Amptec Research 620ES Manual

OPERATION/MAINTENANCE MANUAL
09JUNE2011 REV. E
PHONE [phone]
website http://www.amptec.com
FAX [phone]; TOLL FREE IN USA
2.0 (I.9999) Ohms Fullscale with
0.1 milliohm (100 µ ) Resolution
620ES Safety Igniter Tester
Option "110" Test Lead Pouch

TABLE OF CONTENTS
_______________________________________________________________
CHAPTER A: RECEIVING AND INITIAL INSPECTION
A-1 Introduction to the AMPTEC 620ES series
A-2 Unpacking and Inspection
A-3 AC Adaptor/ Battery Charger- Power Requirements
A-4 Setup and Use
CHAPTER B: 620ES FAILSAFE OHMMETER SPECIFICATIONS
Table B-2. Specifications
CHAPTER C: REPLACEMENT, OPTIONAL AND ACCESSORY ITEMS
C-1 Available Accessories and Options
C-2 Test Lead Sets
CHAPTER D: OPERATION, FUNCTION AND USE
D-1 General
D-2 Front Panel
D-3 4-Wire Resistance Measurement
D-4 Connections
D-5 Failsafe Operation
D-6 Battery Monitoring Circuitry
Figure D-1 Error sources in Resistance Measurements

CHAPTER E: GENERAL OPERATION AND DESIGN
E-1 General
E-2 Troubleshooting
E-3 Circuit Descriptions
E-4 Analog-to-Digital Converter
E-5 Ohms-to-DC Converter
E-6 Failsafe Design
E-7 Ultra-Safe Power Supply Scheme
Figure E-1. Model 620ES Block Diagram
Figure E-1B Analog-to-Digital Converter Timing Diagram
Figure E-2 Analog Section of IC1 and IC2
Figure E-3. Constant Current Source Diagram (Simplified)
Figure E-4. LED Display Pin Functions
CHAPTER F: ROUTINE MAINTENANCE
F-1 General
F-2 Required Test Equipment
F-3 Calibration Procedure
F-4 Battery Replacement Instructions

A-1. Introduction to the AMPTEC 620ES
The AMPTEC 630, 640 and now the 620 Series
Igniter Testers/Failsafe Ohmmeters are
becoming the standard in the Safety Igniter
Circuit Test industry, and are designed to
provide extremely safe and reliable resistance
testing of explosive or volatile devices. Safety
Approvals from various Safety Boards include,
the U.S. Air Force ( 620A-4) for generic use on
Non-Nuclear munitions and the US NAVAL
ORDNANCE CENTER (620AN and other
versions pending). Some of the devices the
620ES Igniter Tester may be used on include:
fuses, squibs, igniters, explosive bolts, rocket
motor squibs, automobile air-bag initiators and
many others.
The AMPTEC 620ES is a 4-wire failsafe digital
ohmmeter which has been designed to reliably
use very low test currents for its resistance
measurement. Failsafe Output Circuitry
proprietary to AMPTEC RESEARCH ensures
that test current levels do not exceed the
specified "failsafe current" even in a worst-case
component failure situation. The failsafe feature
is tested in every instrument before shipment.
The newer 620 series represent the latest in
ultra-safe Igniter Tester measurements. The
620ES uses the same main printed circuit board
(PCB) as all of the AMPTEC 620A Igniter
Testers. The 620ES has many features which
make it useful in a variety of applications.
Please check the last chapter of this manual for
addendums that may apply to the 620ES.
Should the rechargeable batteries reach a low
charge level a negative sign will apear on the
display. The 620ES has a battery monitoring
circuit that indicates it is time to plug in the
battery charger.
A-2. Receiving, Unpacking, and Initial
Inspection
Should the AMPTEC shipping box appear
damaged upon arrival, request that the carrier's
agent (i.e. UPS) be present when the unit is
unpacked. If the 620ES appears damaged, the
carrier's agent should authorize repairs before
the unit is returned to the factory. Even if the
instrument appears undamaged, it may have
suffered internal damage in transit that may not
be evident until the unit is operated or tested to
verify conformance with its specifications.
If the unit fails to operate or fails to meet the
performance specifications of Section B, notify
the carrier's agent and the nearest AMPTEC
Sales Office. Retain the shipping carton for the
carrier's inspection. DO NOT return
equipment to AMPTEC RESEARCH or any
of its sales offices without first obtaining an
(RMA) Return Material Authorization number.
We need to know who to contact and how to
contact (i.e. phone number and FAX number) in
order to properly coordinate the return of the
repaired AMPTEC product.
By calling AMPTEC RESEARCH first, prior
to just returning the 620ES, we can often
troubleshoot (based on the symptoms you
describe) and identify the problem over the
phone (i.e battery loose in the battery holder).
We may possibly be able to fix the problem over
the phone and prevent you from having to return
the unit to AMPTEC for repair.
R M A
SECTION A - RECEIVING AND INITIAL INSPECTION

A-3. AC/DC Battery Charger - Power
Requirements
The AMPTEC 620ES is powered by an internal
rechargeable heavy-duty nickel-cadmium battery
pack (4 ea D cell - 5.0 AHr). Replacement batteries
may be purchased, contact the sale department at
AMPTEC RESEARCH.
The battery charger is an external AC/DC converter
that plugs into a standard 115VAC receptacle. The
AC powered battery charger provides 6VDC @
250mA for charging the AMPTEC 620. The
AMPTEC 620ES is designed so it is impossible to
be powered (in operating - measurement mode)
directly from the AC line battery charger. As an
additional note, the 620ES main power switch must
also be in the “Off/Charging” mode in order for the
connected battery charger to recharge the 620ES’s
batteries.
For customers using 220VAC 50 HZ AC line power
for running the battery charger, please inform
AMPTEC’s sales department at the time of your
order and the appropriate adaptor will be included
with the 620ES Failsafe Ohmmeter shipment for an
additional fee.
A fully charged battery pack typically powers
the 620ES for approximately 6 ~ 8 hours before
requiring a recharge. AMPTEC installs a quality
set of 4 each Heavy Duty (5000 mAHr) Ni-Cad
batteries. The 620ES will also operate on a 4000
mAhr D cell Ni-Cads with a shortened operating
time between charges. Recharge time is
typically twice the “Power On” time. An
“Overnight” charge
usually restores the 620ES to a “Fully Charged”
ready to use state.
The main “Power” switch has two separate
modes. The “ON” position supplies internal
battery isolated power to operate the 620ES
when they are charged. If you turn on the
620ES, and the display does not come on, it
may indicate the batteries need charging. The
“OFF/ CHARGING” power switch position is
for use when the batteries need charging or the
620ES is not in use. As mentioned earlier of
course the AC/DC Battery Charger must be
plugged into the 620ES’s rear panel charging
jack/ connector to facilitate charging the
batteries.
Although the batteries are fully charged prior to
shipment, it may be desirable to refresh the
charge for 24 hours before use. As a rule of
thumb, the 620ES requires twice as much time
to fully recharge as the amount of discharge
time. For example, if the instrument was used
continuously for 2 hours, the AC adapter must
be connected for 4 hours in order to fully restore
the charge. If you need a replacement AC/DC
Battery Charger for the 620, contact the
AMPTEC customer service department and
request an option “620DC” Battery Charger.
Located on left hand portion on the 620ES
display is the “Low Battery” indicator box.
Check for no “Low Battery” indication. If the
LED display shows a negative (-) or minus sign
in the indicator box the unit’s batteries are low
and need charging. The absence of the negative
sign in the battery indicator box indicates the
batteries are acceptably charged.
Fuse
(2 Amp-fast blo)
620ES

When the 620ES is first turned on, the unit
draws more internal power to heat up the unit’s
ovenized zener voltage reference. If the “Low
Battery” Indicator only comes on for a few (i.e
10 to 15 seconds) seconds when the 620ES is
first turned on then goes out, the battery levels
are starting to indicate the charge level is getting
low.
A-4. Setup and Use
The AMPTEC 620ES Igniter Tester may be
setup to operate within minute(s) of power "turn
on" (unless your in an extremely cold
temperature - allow more time for warm-up - 15
minutes). A quick check for no sign of the "low
battery indicator" and test lead integrity check
and it should be ready to use.
Once the AMPTEC 620ES has had it’s batteries
charged for 12 to 24 hours it is ready for use.
The 620ES consumes little power and generates
virtually no heat. Consequently, it may be used
in any area where the environment does not
exceed the specifications of Table B-2.
Avoid exposing the 620ES to extremes of
temperature which will affect accuracy and
shorten battery life-span.

CHAPTER B - 620ES EXPLOSIVE SAFETY
IGNITER TESTER - SPECIFICATIONS
______________________________________________________________
Actual fail-safe currents vary with each instrument and may be ±20% from the typical value.
Table B-2. Specifications
Accuracy: (for 1 year @25°C ± 10°C)
2.0 ohm range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±0.02% of reading ±0.05% of range
20 ohm through 200 ohm ranges . . . . . . . . . . . . . . . . ±0.02% of reading ±0.02% of range
200 Kohm range . . . . . . . . . . . . . . . . . . . . . . . . . . . ±0.05% of reading ±0.05% of range
Temperature Range
Operating 0°C to 50°C
Storage -10°C to 70°C
Temperature Coefficient
20 ohm through 20K ohm ranges ±0.002% per °C (from 0°C-15EC and 35°C-50°C)
Instrument Display . . (20,000 count) 4½ digit Super Bright Light Emitting Diodes (LED)
Over-Range Indication . . . . . . . . . . . . . . . . ( select next higher range) Display flashes
Measurement Update Rate . . . . . Approximately 300ms
Voltage Protection - Maximum Input . . . . 250VDC or AC without damage
peak
Open Circuit Current Source Compliance Voltage . . . . . clamped at ~1.6 volts
Power . . . . (4 "D" 5.0 AHr Heavy Duty) 1.2V rechargeable nickel-cadmium batteries
or OP 247 Continuous Isolated Operating Power
AC/DC Battery Charger (Option DC) provides 6VDC at 250 mA nominal
Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.5" (24cm) W x 11" (27cm) D x 3"(8cm) H
Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 lbs net; 15 lbs shipping
620ES Resistance Range/Resolution 620ES Nominal Test Current/Failsafe Current Levels

C-1. Available Accessories and Options
Listed below are the options available for use with
the AMPTEC 620A Series FailSafe Ohmmeters.
Option 620DC: Battery Charger
Option "DC" is an AC/DC converter that converts
115VAC line voltage to 6VDC at 300mA. One
charger is provided as a standard accessory with
every 620A. A 220 VAC 50 Hz powered Battery
Charger adapter is also available.
Replacement Batteries
The rechargeable Nicad batteries installed in the
620A should provide years of trouble-free operation.
Replacement, however, will eventually be necessary.
The 620A uses four 1.2V cells (5.7 AHr
recommended) installed in a reusable battery box.
When ordering replacement batteries, please specify
AMPTEC Stock #0E-10117, quantity four (4).
Option 100: Carrying Case
Option "100" is a hardshell (impact resistant plastic)
shock absorbing foam lined meter and accessory
carrying case for the 620A Ohmmeter with extra
room for test leads, battery charger, Kelvin Clip Test
Leads, Connector Adapters, single pointed probes
and operator manual etc.
Option RACK: Rack Mount Adapter
Option "620RACK" includes an adapter tray that
allows any AMPTEC 620 series tester to be flush
panel mount installed in a standard 19"
equipment rack.
C-2. Test Lead Sets and Probes
Option “290" Alligator Clip Lead Set
Option "290" is the recommended general
purpose Alligator Clip test lead set (red and
black) for models not having a 2.0 Ohm range
(due to a small resistance “offset” at the tips -
OK for 20 Ohm and higher range units ) . Option
“290" is supplied as a standard item with all
620A-4 (USAF version) ohmmeters as part of
the accessory package. Option “290" is a 48"
long cable set with dual banana plugs at one end.
The other end is terminated with an alligator clip
( red and black) . Some “Squib Resistance” test
panel jacks have a plastic exterior with a
conductive socket center. These alligator clips
will measure (2 wire method) properly with
either upper or lower jaw connected to the
conductive socket center of plastic test panel
jacks. Kelvin Clips see Option “300” (using the 4
wire method) may have difficulty only if both
jaws (both upper and lower) do not make
electrical contact with the conductive “resistance
under test” center.
See next page for Kelvin Clips and other
accessories.
SECTION C OPTIONAL ITEMS AND
ACCESSORIES

Option 401: Handheld Single Probe Leads
Option "401" is a 620 series compatible handheld
probe (one black probe & one red probe ) lead set
terminated in single points. The OP401 handheld
probes allow for easy access to connector socket
wiring (i.e. drone parachute squib sockets), recessed
surfaces, and parts (i.e. flares) that alligator clip
leads simply would not work well with.
Option “500” Optically Isolated Analog Output
Option “600” Optically Isolated Binary Coded
Decimal (BCD) Data Output
New Options and Custom Leads Available
Contact the sales department at AMPTEC
RESEARCH (phone [phone]) if you have
need for GPIB, a special probe, adapter, lead set, or
custom option not listed in this manual. AMPTEC’S
experienced application engineers have helped sup-
ply many customers with special igniter tester acces-
sory requirements.
This rear panel mounted isolated analog DC Voltage
output signal is directly proportional to the 620
tester's ohm display measurement. (i.e. 1.2345 VDC
for 12.345 ohms). It is used to track 620 tester mea-
surements for datalogging purposes with an external
device (i.e chart recorder, system DMM with GPIB).
Isolation protection is rated @2000 volts peak to
insure any instrument connected to "Option 500" has
virtually no impact on the 620 series tester's safety.
For applications requiring data output the 620 series
is available with “BCD”output. The measured resis-
tance readings are output via a rear panel “BCD” talk
only interface. A High- Go- Low BCD Dual Limit
Comparator is presently under development and will
be available Summer of 2001..
Option 300: 4-Wire Gold Plated Kelvin Lead Set
Option "300" is a general purpose Gold Plated
Kelvin four wire Leads for all AMPTEC 620 series
Testers. Gold plated kelvin clips provide a low
thermal EMF connection (minimizes the thermo-
couple effect) with most connections. The Option
“300” is the recommended test lead set for any
AMPTEC Igniter Testers with a 2.0 Ohm range
(i.e models 630ES and 620ES). The 4 wire Kelvin
connection is important when measuring less than
1.0 ohm, and also automatically eliminates test
lead length offset and test lead contact resistance
errors. Option “300” is a shielded 48" lead set
terminated in ½" opening gold plated Kelvin clips.
The option "300" can clip easily to wires, pins, and
medium size (up to ½" diameter conductors). The
dual banana plug ends connect directly to the 620
tester's front panel input terminals. (see Option
"320" for replacement Kelvin clip ends only)
Option 305: Banana-to-Banana Cable
Option "305" is a 48" shielded cable terminated in
dual banana plugs at both ends.
Option 320: Kelvin Clips
Option "320" are the gold plated kelvin clips used
on the Option "300" cable set . These clips may be
used when making custom cables or when repairing
Option "300".
Option 360: Heavy-Duty Clips
Option "360" are Gold-plated jumper cable (large
jaws) type clips used on the Option "350" cable.
They are still Kelvin Clips because the insulated
upper and lower jaw (jumper cable appearance)
integrity is maintained. These may be used when
making custom heavy duty cables that open to 1
1/2 " wide (i.e bolt heads)..

Functional Test Section - The optional 620ES Functional Test Box provides added measurement integrity
using a milliammeter and test resistors to cross check the overall 620ES operation whenever desired. The
test resistors are for cross checking 620ES basic operation and should not be used for calibration purposes.
Simpsontm DC Milliammeter Range - 0-10 mA fullscale, Accuracy ±3%
FTSR1 01-23572 0.1W 1.0 % Resistor, Tc- 25ppm/°C, ¼ W
FTSR2 01-23575 10.0W < 0.1% Resistor, Tc- 10ppm/°C , ¼ W
FTSR3 01-23577 10.0 KW <0.1% Resistor, Tc- 10ppm/°C, ¼ W
FTSR4 01-23583 100 KW <0.1% Resistor,Tc- 10ppm/°C, ¼ W
FTSR5 01-23587 10.0 MW <1.0% Resistor, Tc- 20ppm/°C, ¼ W
FTSR6 01-23589 19.0 MW <1.0% Resistor, Tc- 50ppm/°C ,¼ W
MILLAMPERES
2
4
6
8
10
100.0 KOHM
10.0 KOHM
10.0 OHM 10.0 MOHM
620ES
Functional
Test
Box
19.0 MOHM

If the resistance being measured (including
"Open Circuit/ Disconnected states") is a higher
value than the selected range, the instrument's
display will flash (blink) , which indicates
"overrange" .
Gold Plated Five way
Input Jacks
The AMPTEC 620 front panel input jacks are a
gold plated variety that readily accept a number
of user connection modalities. The unit's
banana post input jacks may be unscrewed
several turns to exposed a horizontal hole thru
the gold plated post. The AMPTEC 620 user
can directly connect a bare wire thru the banana
post (horizontal hole). Once the wire is thru the
banana post hole you can hand tighten the
banana post to make a secure electrical
connection. The AMPTEC 620 front panel
input posts also accept wires with spade lugs,
and or banana jacks. The 48” long dual banana
Alligator Test Leads plug directly into the
Voltage High and Voltage low , and Current
high and Current low panel jacks. The spacing
of the AMPTEC 620 panel jacks only allows
horizontal connection of the dual banana jack
test leads to prevent mis-connection.
Calibration Access Screws
Recessed in the four feet on the bottom of the
AMPTEC 620ES you will note there are 4
screws (phillips head type) that are used for
calibration access. These screws are meant to
remain intact and should only be removed by
authorized personnel (i.e. Calibration Lab staff).
Optional Functional Test Box with built-in
milliammeter
An optional Functional Test Box (option FTB-
620ES) for the AMPTEC 620ES contains an
analog 10 mA full-scale milliammeter and a
variety of test resistors is available from
AMPTEC RESEARCH.
D-1. General Operation
This section contains operating instructions for the
AMPTEC 620ES Explosive Safety Igniter Tester.
D-2. Front Panel Features and Operation
Main Power Switch
When the front panel power switch is in the OFF
/CHARGE position, all power is removed from
the ohmmeter measurement circuitry, and the
battery pack is connected to the rear panel
charging circuit. When the main power switch is
placed in the ON position, the unit's battery pack
is disconnected from the charging circuit. The
possibility of a common mode voltage between
the device under test and AC Power ground is
therefore completely eliminated. The operator
need not be concerned if the battery charging
adapter is plugged into the AMPTEC 620ES as it
is disconnected during any resistance
measurements.
Range Switches
model 620A-4 shown
The AMPTEC 620 series ohms ranges are selected
by pressing the desired range switch on the front
panel. The range select pushbutton for the lowest
resistance range ( leftmost resistance range button)
indicated above the range select buttons. When a
given range is selected (pushed in) the other range
switches "pop-out" and inform the user. It is
obvious to the 620 user which resistance range has
been selected, as it is the only range button pushed
in. Also note that a resistance range should be
selected after powering up the 620ES in order to
place it in an operational mode. After turn "ON", a
range should be selected. For new instrument
users with a 200 Ohm range AMPTEC Igniter
Tester, the unit will measure resistances up to 200
Ohms.
x
x
CHAPTER D - OPERATION, FUNCTIONAL
AND USE

AMPTEC 620ES Rear Panel with RS232C I/O
The AMPTEC 620ES rear panel (shown above) contains
many jacks, terminals, labels, and stickers.
The AC to DC Adapter (item #1) must be left in the
rear panel jack in order to continuously operate the unit,
if fitted with option "247". If configured with NICAD
batteries then this is the battery charger jack and the
620ES will only charge when the power switch is in the
"OFF" position. ( battery powered units only).
Item 2 is the fuse holder - replace with a 2 ampere 3 AG
type fast blow fuse (rarely needs replacing).
RS232C Serial Interface - Item # 3 is the safety isolated
RS232C serial I/O (9 pin D type Sub-min connector ).
This RS232C Interface provides the meter’s resistance
measurements to a PLC fitted with a serial port. The
RS232C protocal settings should be 9600 Baud, 8 Bits
, No parity , 1 Stop Bit , 9 pin D Sub-min connection.
RS232C Command Set
(NOTE: All front panel range buttons must be de-
selected (press in half way) with all range pushbuttons
out in order to disable with local lockout and enable
RS232C control. Note commands are case sensitive.
C Continuous Read Mode - RS232C I/O outputs
a data string every A to D conversion cycle, approx. 2.5
times per second.
S Single Read Mode - RS232C I/O outputs a
single data string upon reception of a “R” command.
R Read - Commands RS232C I/O to output a
single data string ( 1 resistance reading).
r0De-Selects all Ranges
r1 Selects the 2.0 Ohm Range
r2 Selects the 20 Ohm Range
r3 Selects the 200 Ohm Range
r4 Selects the 200K Ohm Range
VVersion commands board to output the firmware
version string.
*
Data Format - The RS232C I/O outputs a data
string with the following format:
1.2345E+3 The measurement is always in Ohms
+3
(where E+3 = 10 scientific notation style) . The
Exponent is defined below. 1.2345E+3 = 1.2345
+3
+3
KOhms (where E =10 ). 1.3700E+1 = 13.700
+1
+1
Ohms (where E =10 )
Range Exponent
2.0 Ohm E+0
20.0 Ohm E+1
200.0 Ohm E+2
2.0 K Ohm E+3
20 K Ohm E+4
200 K Ohm E+5
An overrange condition is indicated by
9.9999Enn..Where nn is the selected resistance
range exponent. A Range Error is indicated by
x.xxxxERR.
Item # 4 is the unit’s serial number sticker.
Item # 5 is the gold plated 4 terminal rear terminal
strip (they are wired in parallel with the front termi-
nals). If a “2 wire ohms” connection is made then
the V high and I high terminals should be shorted
together, and the V low and I low terminals should
be shorted. The 620ES Voltage High, Voltage low,
Current high and Current low wires are perma-
nently connected to the gold plated rear terminal
strip ( seel labeled gold plated terminal strip on rear
panel).
Item #6 Calibration Sticker - If the calibration
due date has expired ( 1 year) AMPTEC or a Cal.
Lab can contacted to re-certify the AMPTEC
620ES Explosive Safety Ohmmeter/Igniter Tester.
contact AMPTEC customer service see website
www.amptec.com

The optional FTB-620ES's on-board milliam-
meter provides an independent verification of
the AMPTEC 620ES's output current levels are
less than 10 mA. The 620ES failsafe current
circuitry limits the 620ES such that one should
never see a current level of 15.0 mA or higher.
With one test lead (i.e. red ring tipped banana )
plugged into the meter panel jack and the other
test lead (i.e. black ring tipped banana jack)
plugged into the common panel jack, the
milliammeter will display the actual test current
coming from the 620ES Igniter Tester, when the
test leads are connected and the 620ES is in
operation mode. The span of the DC
milliammeter is 0 to 10 milliamperes full-scale.
If the test leads are connected backwards to the
620ES DC milliammeter being DC based will
not measure.
The test resistors of the FTB-620ES may also
be used to verify general 620ES operation and
functionality. Keep in mind the proper resis-
tance range should be selected in order to mea-
sure a selected test resistor. You can’t measure a
1000 ohm resistor on the 200 ohm range of the
620ES. With one test lead (i.e. red banana lead )
plugged into the selected test resistor panel jack
and the other test lead (i.e. black banana lead)
plugged into the common panel jack, the 620ES
Igniter Tester should display a resistance value
close to the labeled value of the resistor. The
0.1 ohm resistor is commonly used to test the
bottom or low end
(i.e. linearity) of a given 620ES resistance
range. The 0.1 ohm resistor can be used to
check the 620ES’s zero offset.
Refer the AMPTEC 620ES to qualified service
personnel (i.e Calibration Lab) if you suspect
(i.e large error) the 620ES measurement display
readings don’t agree with the resistor values
labeled on 620ES Function Test Section. Do not
attempt to repair the 620ES unless you are
qualified.
D-3. 4-Wire Resistance Measurement
The four-terminal configuration of the 620ES
eliminates measurement errors normally caused
by "in series" test lead resistance and "contact"
resistance.
In many resistance measurement applications the
contact resistance and can exceed the value of
the test resistance by several orders of magni-
tude. The AMPTEC 620ES overcomes this
potential error source by providing two terminals
of constant current (I high and I low) and an
additional two terminals for high impedance
voltage measurement. The constant current
source uses a variable compliance voltage circuit
to overcome lead and contact resistance until the
current loop is a constant level. The result is a
fast, accurate resistance measurement of the test
resistance, independent of the resistance of the
current carrying leads.
Figure D-1 above illustrates the 4-wire principle
eliminates 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 polarities of
the constant current source 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 (Vhi and Vlow) leads.
D-4. Connections
Connections are made to the front panel termi-
nals using a 4-wire configuration as described in
section D-3.
IGNITER TESTER
Figure D1 - Igniter Tester Kelvin Block Diagram
* contact resistance
*
*
IGNITER
LEAD RESISTANCE
LEAD RESISTANCE
P
O
O
L
T
N
E
R
R
U
C
DC to DC ISOLATOR
HIGH IMPEDANCE VOLTMETER
4.8 VDC BATTERY
DC to DC ISOLATOR
COMPLIANC
VOLTAGE
LIMITED
CONSTANT
CURRENT
SOURCE
E

Next connect the 4 wire Kelvin (Option "300")
Clip Test Leads into the AMPTEC 620 Igniter
Tester . The AMPTEC 620 front panel input jacks
are spaced to only allow horizontal access (i.e. V
high and I high) if using dual banana jacks. All
AMPTEC 620ES Kelvin 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 gold plated clip jaws (upper
and lower jaws). One Kelvin Clip for current and
voltage high, and another Kelvin Clip for current
and voltage low.
For 620 series test leads other than those termi-
nated with banana plugs, RG-58 Shielded Coax
Cabling is recommended. Customer built test
wiring should maintaining the four wire Kelvin
measurement if possible. Make the current con-
ductor the largest conductor and keep the voltage
sense input shielded or inside the current shield.
The AMPTEC 620 series Igniter Tester's five way
input jacks allow for customized wire connec-
tions, extended kelvin wiring (beyond 100 feet
depending upon conductor gauge), cables termi-
nated with spade lugs, and special banana jacks
can all be used with the AMPTEC 620 Tester.
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 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 wan-
dering. The display may indicate a randomly
wandering number or it may indicate an
overrange (flashing) condition. This unpredict-
able display (No input to the DVM) condition is
not a malfunction, in fact, just a characteristic of
the high impedance voltmeter circuit and should
not be mistaken for a fault in the instrument - As
this condition is simply a state of an “open cir-
cuit” or “nothing connected” to the DVM cir-
cuitry. A flashing display (on and off usually all
zeros) indicates an over-range condition when-
ever the test lead terminals are open, or the resis-
tance under test is a higher value than the range
selected on the AMPTEC 620 tester. Connecting
VHI to IHI and Vlo to Ilo eliminates the wander-
ing (open circuit) display condition.
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
low low
instrument 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, 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 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.
Identifying a Test Connection problem
A precision 1.0 Ohm test resistor is also located
in the optional Functional Test Box (FTB-
620ES) available from AMPTEC. The 1.0 Ohm
test resistor can be used for testing mid-scale
performance of the 2.0 Ohm range. Performing
a similar Functional Test with the 620ES meter
across the 1.0 Ohm test resistor should get a
reading close to 1.00 Ohm (i.e. 0.9995 Ohms is
OK). If the 620 Series Igniter Tester appears
OK after checking the test resistors in the
Functional Test Section then the connection
problem must be outside of the 620 series meter
(i.e your wiring harness or the actual device
under test connection.) If the 620 series meter
doesn’t agree with the test resistors in the
Functional Test Box, 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)
447-7456 (International Overseas) or FAX
[phone], email [email protected]

The AMPTEC 620 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 problem isolation and diagnosis envolves
general trouble-shooting principles. If a
measurement problem appears on the 2.0 Ohm
range of the meter, test for a zero offset problem
first. Plug the 620 with Kelvin test leads into a
0.10 test resistor (i.e. AMPTEC # FTB-620ES).
If the meter doesn’t display a value close to 0.1
Ohms adjust the zero (see calibration procedure
chapter). The zero adjustment trimpot only has
enough span to zero out the 620 series test leads.
The meter’s zero adjustment pot wasn’t
designed to zero out a 100 feet of 2 wire
harness.
D-5. Failsafe Operation
The AMPTEC 620 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 with
most AMPTEC models under the corresponding
range switch on the 620 series meter front panel.
Please refer to section E-6 for a technical
description of the failsafe circuitry specifics.
As a further precaution the 620 Series Igniter
Tester is isolated from the AC line whenever the
POWER switch is in the ON position.
The 620 series igniter tester receives its power
from an internal rechargeable battery pack (4
“D” Cell Ni-Cad batteries). The 620 series
igniter tester “main power” switch (see item 12
of the 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 rear panel jack. .
The “main power switch” must be switched
“OFF” to charge the batteries. In the "OFF"
position, the main power switch disables all
ohmmeter measurement circuitry and connects
the internal battery pack to the charging jack
(Safety Feature).
Constant Current Circuit Operation
Assume that terminals I and I of Figure E-3 are
hi lo
shorted, and 0.5 volt is applied to E so that I is
in hi
positive. To equalize the 0.5 volt applied to Ein ,
the inputs of IC202, IC201 must be driven to
zero. This condition occurs only when the
voltage drops across R212 and R222 are equal to
the drops across R213 and R221. For these
voltage drops to be equal, the output of IC202
must be at +1.0 volt. Since the output of IC201
must be zero, the drop across R213 is 0.5 volts,
making the inverting input 0.5 volts. The drops
across R212, R221 and R222 will also be 0.5
volts. Since the inputs to IC201 are essentially
equal, its output is zero (offset by the few
microvolts required to drive IC202 to +1.0 volt).
Under these conditions the sum of the voltages
across R212, R213 , R221 and R222 equals the
sum of E plus the output of IC202.
in
Consider now that the short is removed from the
I and I terminals and a 100-ohm resistor (R ) is
hi lo L
connected in its place. The current through R
L
increases the voltage at the input to IC201. A
balanced condition will be reached when the
output of IC201 is equal to the non-inverting
input of IC202. Again, this condition occurs
when the voltage drops across R212 and R222
are equal to the voltage drops across R213 and
R221. At this time the output of IC202 is 1.0 V.
The 620ES Explosive Safety Igniter Tester
measurement circuitry is failsafe current limited,
even under worst case component failure.
For the 620ES Explosive Safety Tester the normal
or typical operating current level is less than 10
mA, and <15 mA on 20 Ohm range as a Failsafe
Level .
The voltage drop across the range resistor is 1.0
V, just as it was when the output terminals were
shorted. The current through R is 10 mA, just as
L
it was through the jumper when the output
terminals were shorted.

R212
100K
R213
100K
R222
100K R221
100K R215
100K
RANGE
ATTENUATION
RESISTOR
RL
I hi
I Lo
E in
Figure D-5 Constant Current Circuit
IC201 IC202
limits, because the -5 volt and +5V supplies
includes inherent current limiting. Because of the
design of both supply isolation transformers T101
and T102, the ±5 volt supplies can only deliver 20
to 25 milliamperes before the DC/DC converter
disengages, dropping the -5 volt output to zero.
620ES Failsafe Current Calculation - Worst
Case Component Failure
Please refer to Section E for a more detailed
explanation of the failsafe current source.
D-6. Battery Monitoring Circuitry
The 620 series igniter tester display has a ±
polarity display indicator preceding the unit’s
regular 4 ½ digit numeric display. The negative
polarity display LED is used as a Low Battery
indicator. If the low battery LED is illuminated,
620 Series Igniter Tester readings should not be
trusted. An overnight recharge should be
performed before using the 620 series igniter tester
for critical testing. The batteries are fully charged
prior to shipment, it may be desirable to refresh the
charge for 24 hours before use. As a rule of
thumb, the 620ES requires twice as much time to
fully recharge as the amount of discharge time.
Notice for Cal Lab: The variable trimpot RV3 is
factory adjusted to have the low battery indicator
come on at 4.50 VDC. To make this adjustment
refer to the Maintenance Section F of this
manual.
Voltage limiting diode, D203, provides a 1.6 volts
maximum across R227 (100W) and R223 (100W),
which are 200 Ohms across the Igniter Testers
output terminals.
(Imax) Current Maximum Calculation
1.6V/110 ohms = 0.014 Amperes (15mA) max
A simple startup test procedure which also has the
620ES Explosive Safety Tester user perform a
functional check using (optional FTB-620ES) with
AMPTEC milliammeter would also detect any
current level even getting close to the Failsafe level.
igniter could not exceed safe
Reference to the AMPTEC 620ES Igniter Tester
schematic will show that the output of IC202-6 is
actually applied to the base of transistor Q202,
which acts as a current limiter. The worst-case
component failure that could occur in this circuit
would be a Q202 short, which would effectively
connect the -5 volt supply directly across R218,
D202, the range resistor and R .
L
D203, however, acts as a 1.6 volt zener diode,
limiting the voltage that can appear across the
current output terminals. Even if every
component in the amplifier circuit shorted, the
current through the
MILLAMPERES
2
4
6
8
10
100.0 KOHM
10.0 KOHM
10.0 OHM 10.0 MOHM
620ES
Functional
Test
Box
19.0 MOHM
Functional Test Section - The optional 620ES
Functional Test Box provides added measurement
integrity using a milliammeter and test resistors to
cross check the overall 620ES operation whenever
desired. The test resistors are for cross checking
620ES basic operation and should not be used for
calibration purposes.
Simpsontm DC Milliammeter Range - 0-10 mA
fullscale, Accuracy ±3%
FTSR1 01-23572 0.1W 1.0 % Wirewound
Resistor, Tc- 25ppm/°C
FTSR2 01-23575 10.0W < 0.1%
WirewoundResistor, Tc- 10ppm/°C
FTSR3 01-23577 10.0 KW <0.1% Wirewound
Resistor, Tc- 10ppm/°C
FTSR4 01-23583 100 KW <0.1% Wirewound
Resistor,Tc- 10ppm/°C
FTSR5 01-23587 10.0 MW <1.0% Wirewound
Resistor, Tc- 20ppm/°C
FTSR6 01-23589 19.0 MW <1.0% Wirewound
Resistor, Tc- 50ppm/°C

CHAPTER E GENERAL OPERATION AND DESIGN
E-1. General
The AMPTEC RESEARCH 620ES Explosive
Safety Igniter Tester is shown in the block dia-
gram (Figure E-1). All diagrams and informa-
tion disclosed in this chapter is proprietary and
is included in order to make troubleshooting to
component level possible.
The AMPTEC 620 Series Igniter Tester uses
modern solid-state semiconductors exclusively
and digital CMOS circuits extensively to mini-
mize power requirements and make battery
operation useful and practical. AMPTEC also
maintains a spare parts inventory of all compo-
nents found in the 620ES Tester and it’s cus-
tomer service department can also provide
additional assistance in the trouble shooting
process.
E-2. Troubleshooting
Since the 620ES Tester is used to test potential
deadly explosive force detonators and warheads
of missiles etc., personnel that are not qualified
to make such electrical repairs on the 620ES
Tester should not even attempt to remove the
calibration access screws or open the main
panel or effect any repair whatsoever.
Apparent 620ES Tester malfunctions can some-
times be the result of bad test lead/connection
wiring, wrong connections, misinterpretation of
specifications, low battery levels, and in rare
cases due to an incomplete understanding of the
instrument and how to use it. A thorough review
of the operating instructions for this instrument
is recommended prior to any component
replacement. Check to be sure that cables and
other test equipment are in good working order
before attempting to troubleshoot the 620ES
series igniter tester .
If you turn on the AMPTEC 620ES Explosive
Safety Igniter Tester and the display does not
come on, it usually means the batteries are
dead and need charging, or fuse needs replac-
ing.
If the 620ES exhibits problems that cannot be
eliminated by reviewing Chapters B and D, the
following guidelines have been established to
help solve the problem.
E-2-1. Localizing the Problem
Chapter D-2 discusses how to use the
Functional Test Box (FTB-620ES) with the
620ES Tester to help localize the problem. The
key to successful troubleshooting is to localize
the problem to a general electronic parameter as
much as possible before trying to pin the
problem down to a specific component. Certain
questions should be asked such as "Does the
problem occur on all ranges or on a specific
range only?". If the 620ES Tester does not
come on when powered up, did you check the
rear panel fuse. The power supplies for both the
current source and the digital voltmeter
electronics are also one of the first things that
should be tested. As it is not possible to
anticipate all failure modes of the 620ES
Explosive Safety Igniter Tester, servicing
personnel should become familiar with this
section to gain a complete understanding of the
internal workings of the ohmmeter.
E-2-2. Component Replacement
If the malfunction is a faulty component, the
accuracy of the 620 Series Igniter Tester can be
maintained only if it is re-calibrated after a
component replacement and the following
precautions are taken:
Use only the specified component or its exact
equivalent. Spare parts can be ordered from
your nearest AMPTEC RESEARCH Service
Center or directly from the factory by referring
to the AMPTEC Stock Number listed in the
Parts Lists section at the back of this manual.
The highest quality 63/37 grade rosin core
electronic grade solder with a 50W or lower
maximum power soldering iron should be used.
Never use an acid core solder as corrosion of
components leads and PCB etch loss can occur.

When soldering, heat the PCB pad and the lead
of the component, not the solder. After several
seconds of the component lead in contact with
the hot soldering iron apply solder smoothly and
evenly onto the PCB pad and component lead
not the soldering iron. Do not touch or move
the replacement part until the solder has cooled.
Cold solder and bad solder joints can cause
more problems.
Use the chassis ground (connect to the common
terminal of the functional test section)
connection - i.e. connect to an earth ground to
avoid a static discharge to a static sensitive
component. Handle all 620ES internal
components as if they are static sensitive if you
are not sure.
See Next Page for Start of 620 Circuit Descriptions and Functional Diagrams

E-3. Circuit Descriptions
The circuit descriptions which follow are
referenced to Figures E-1, E-2, E-3 and the
schematic diagrams at the back of this manual.
In the following descriptions, references to
integrated circuits are given in the form "IC201-
1", which refers to Integrated Circuit 201, pin 1.
E-4. Analog to Digital Conversion
The A to D conversion is done with a ICL8068
/ICL71C03 chip set. The ICL8068 takes care of
the analog part and the ICL71C03 takes care of
the digital part of the 4 ½ digit 20,000 count
dual slope conversion.
COUNTERS
DISPLAY
COMPARATOR
BUFFER
MULTIPLEXER
ZERO
CROSSING
DETECTOR
INTEG
UUT
CONTROL
LOGIC
INPUT
SWITCH
DC CONSTANT
CURRENT SOURCE
RANGE
SWITCH
Figure E1 - AMPTEC 620ES FUNCTIONAL BLOCK DIAGRAM
COUNTS
PHASE I
I0.00I I0.000 20.00I
4 ½ DIGIT
PHASE II PHASE III
NUMBER OF COUNTS TO ZERO CROSSING
PROPORTIONAL TO VIN
AFTER ZERO CROSSING,
ANALOG SECTION WILL BE
IN AUTOZERO CONFIGURATION
BUSY
OUTPUT
INTEGRATOR
OUTPUT
CLOCK
AZ PHASE l INT PHASE ll DEINT PHASE ll AZ
INTERNAL
LATCH
POLARITY
DETECTED
ZERO CROSSING
OCCURS
ZERO CROSSING
DETECTED
Figure E1B - 620 Conversion Timing Diagram

ZERO CROSSING
DETECTOR
BUFFERBUFFER
1 µF
INTEGRATOR
COMPARATOR
CAZ
CSTRAY
RINT
FIGURE E-2A. PHASE l AUTO-ZERO
CINT
VIN
CREF
3
1
2
6
5
4A2
A1
A3
_
+
_
+
_
+
ZERO CROSSING
DETECTOR
ZERO CROSSING
DETECTOR
POLARITY
FF
POLARITY
FF
BUFFER
BUFFER
BUFFER
BUFFER
1 µF
1 µF
INTEGRATOR
INTEGRATOR
COMPARATOR
COMPARATOR
CAZ
CAZ
CSTRAY
CSTRAY
RINT
RINT
FIGURE E-2B. PHASE ll INTEGRATE INPUT
FIGURE E-2C. PHASE lll AND DE-INTEGRATE
CINT
CINT
VIN
VIN
CREF
CREF
3
3
1
1
2
2
6
6
5
5
4
4
A2
A2
A1
A1
A3
A3
_
+
_
+
_
+
_
+
_
+
_
+
ZERO CROSSING
DETECTOR
POLARITY
FF
BUFFERBUFFER
1 µF
INTEGRATOR
COMPARATOR
CAZ
CSTRAY
RINT
FIGURE E-2D. PHASE lll AND DE-INTEGRATE
CINT
VIN
CREF
3
1
2
6
5
4A2
A1
A3
_
+
_
+
_
+
Figures E2. Main Analog Section of DVM Circuit - IC1 and IC2