Amptec Research 620A-4 Manual

T.O 33D5-14-52-1
OPERATION / MAINTENANCE MANUAL
AMPTEC RESEARCH MODEL 620A-4
FAILSAFE DIGITAL OHMMETER/
IGNITER CIRCUIT TESTER
NSN 6625-01-460-1499AQ
DISCLOSURE NOTICE: This Information Is furnished upon the condition that It will not be released to
another nation without the specific authority of the Department of the Air Force of the United States, that it
will be used for military purposes only, that individual or corporate rights originating In the information,
whether patented or not, will be respected, that the recipient will report promptly to the United States, any
known or suspected compromise, and that the Information will be provided substantially the same degree
of security afforded it by the Department of Defense of the United States. Also, regardless of any other
markings on the document, It will not be downgraded or declassified without written approval of the
originating United States agency.
DISTRIBUTION STATEMENT: Distribution authorized to U.S. Government agencies only, administrative or
operational use, 18 August 1992.. Other requests for this document shall be referred to O0-AI.C/TIED, Hill
AFB, Utah 84056-5820.
WARNING: This document contains technical data whose export Is registered by the Arms Export Control
Act (Title 22, U.S.C., Sec 2751 et seq) of the Export Administration Act of 1979, as amended (Title SO, U.S.C.,
App 24O1 et seq). Violations of these export laws are subject to severe criminal penalties. Disseminate In
accordance with provisions of AFI 61-204.
HANDLING AND DESTRUCTION NOTICE: Comply with the distribution statement and destroy by any
method that will prevent disclosure of contents or reconstruction of the document.
Published under authority of the Secretary of the Air Force
18 JULY 2000
ORIGINAL
AMPTEC RESEARCH IS AN ISO 9001:2015 CERTIFIED QUALITY MANAGEMENT COMPANY

OPERATION/MAINTENANCE MANUAL
REV. G
AMPTEC 620A-4 Fail Safe
Digital Ohmmeter /Igniter Tester
LOW
BATTERY
Mil Std 810- Method 511 rev F certified compliant for
use in " Volatile Fuel Air Atmospheres "
PHONE [phone]; FAX [phone]; TOLL FREE IN USA 800-350-5105
website http://www.amptec.com e-mail [email protected]

TABLE OF CONTENTS
_______________________________________________________________
SECTION A: RECEIVING AND INITIAL INSPECTION
A-1 Introduction to the AMPTEC 620A 4
A-2 Receiving, Unpacking, and Initial Inspection
A-3 AC Battery Charger- Power Requirements
A-4 Setup and Use
A-5 Serial Number, Revision and Safety Board Approvals
SECTION B: 620A 4 IGNITER TESTER /
FAILSAFE OHMMETER SPECIFICATIONS
Table B-2. Specifications
SECTION C: OPTIONAL ITEMS AND ACCESSORIES
C-1 Available Accessories and Options
C-2 Test Lead and Probe Sets
SECTION D: OPERATION AND USE
D-1 General
D-2 Front Panel
D-3 Rear Panel
D-4 4-Wire Resistance Measurement
D-5 Connections
D-6 Failsafe Operation
D-7 Battery Monitoring Circuitry
Figure D-1. Error Sources in Resistance Measurements

SECTION E: THEORY OF OPERATION
E-1 General
E-2 Troubleshooting
E-2-1 Localizing the problem
E-2-2 Component Replacement
E-3 Circuit Description
E-4 Analog-to-Digital Converter
E-4-1 Reference Voltage
E-4-2 LED Display
E-5 Ohms-to-DC Converter
E-5-1 Constant Current Source
E-5-2 Constant Current Circuit Operation
E-6 Failsafe Design
E-7 Ultra-Safe Power Supply Scheme
SECTION F: ROUTINE MAINTENANCE
F-1 General
F-2 Required Test Equipment
F-3 Calibration Procedure
F-4 Battery Replacement Instructions
E-8 Relay Board General Operation

A-1. Introduction to the AMPTEC 620A-4
The AMPTEC 620A and the 630 Series Igniter
Testers/Failsafe Ohmmeters have become the
standard in the Safety Igniter Circuit Test
industry, and are designed to provide extremely
safe and reliable resistance testing of electrically
explosive devices (EEDs) or “current sensitive”
blasting devices. Approvals from various Safety
Boards include, the U.S. Air Force ( 620A-4) for
use on Non-Nuclear munitions provided the
appropriate T.O. is available. In addition the US
NAVAL ORDNANCE CENTER has approved
the AMPTEC 630AN, 630BN and 640N Igniter
Testers and other versions are pending. Some of
the devices the 620A Failsafe Ohmmeter may be
used on include: fuses, squibs, igniters,
warheads, explosive bolts, rocket motor squibs,
drone parachute squibs, automobile air-bag
initiators and many others.
The AMPTEC 620A-4 is a 4-wire Kelvin (i.e.
eliminates contact resistance errors) failsafe
digital ohmmeter which has been designed to
use safe levels of DC current for its DC
resistance measurement. Failsafe Output
Circuitry proprietary to AMPTEC RESEARCH
ensures that test current levels do not exceed the
specified "failsafe current" in a worst-case
component failure situation. The failsafe feature
is tested in every instrument before shipment.
The AMPTEC 620A-4 represents the latest in
ultra-safe Igniter Tester measurements. The
620A-4 (serial numbers 620A4-800 and higher)
Igniter Testers all use the same main printed
circuit board (PCB) referred to as Revision D.
Please check the Appendix of this manual for
any addendums that may apply to any
differences between the newer (rev D.) version
620A-4s and older (rev C.) 620A-4 Igniter
Testers with serial numbers less than 620A4-800
(i.e. 620A4- 525).
Should the rechargeable batteries reach a low
charge level, a minus sign will appear on the
display. The 620A-4 has a battery monitoring
circuit that indicates when to charge the
batteries.
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 620A 4 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.
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 number
(Return Material Authorization). 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. After getting an RMA #
from AMPTEC, as an added precaution against
loss, be sure to also affix an ID label (contact
info) on the lid of the 620A Igniter Tester with
your phone number, name, address and FAX
number, and email address. By calling
AMPTEC RESEARCH, prior to returning
the 620A, we can often troubleshoot and
identify the problem (i.e. battery loose in the
battery holder), over the phone.

A-3. AC/DC Battery Charger - Power
Requirements
The AMPTEC 620A 4 uses an internal
rechargeable heavy-duty nickel-cadmium
battery pack (4 D cells - 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 battery charger outputs 6.0
VDC @ 100 mA. The battery charger circuitry
is configured such that the 620A-4 main power
switch must also be in the “OFF” position.
The 620A-4 main power “On/Off” switch
design makes it impossible to be powered (in
operating - measurement mode) directly from
the AC/DC Battery Charger. When the 620A-4
main power switch is in the “On” position the
rear panel charging jack is electrically
disconnected from all 620A 4 circuitry.
A fully charged battery pack typically powers
the 620A 4 for approximately 8 hours before
requiring a recharge. AMPTEC installs a quality
set of 4 each Heavy Duty (5000 mAHr) Ni-Cad
batteries ( option 620-BAT) set of 4 ea.. The
620A 4 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 620A 4 to a “Fully
Charged” ready to use state.
If you turn on the 620A-4, and the display does
not come on, it may indicate the batteries need
charging.
The diagram on the right shows a rear panel
view of the 620A Igniter Tester. To check the
fuse, remove the cap from the fuseholder. The
620A uses a 2 ampere fast blow (3AG size).
Only replace with an identical rated fuse.
A spare or replacement battery charger (option
“620-DC”) or replacement set of 4 each heavy
duty NICAD batteries (option "620-BAT") may
be purchased if needed, contact the sales
department at AMPTEC RESEARCH.
The “OFF/ CHARGING” power switch position
is for use when the batteries need charging or
the 620A-4 is not in use. As mentioned earlier
the Battery Charger (115 VAC 60 Hz powered )
must be plugged into the 620A-4’s rear panel
charging jack 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 620A 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.
use Ho de w th F seF lriu
ha i ck
Crg ng Ja
620A Battery Charger
Option "620-DC"

Additional note - Main switch Power “On”. When
the 620A Igniter Tester is first turned on, the unit
briefly draws more internal power then cuts back
to less than 100 mA, after a few seconds. The
initial Power “On” battery drain is to heat up the
unit’s ovenized zener voltage reference. If the
“Low Battery” Indicator only comes on (i.e. 10 to
15 seconds) for a few seconds (i.e. when the 620A
is first turned on), then goes out, the battery levels
are starting to indicate the charge level is starting
to get low.
A-4. Setup and Use
Once the AMPTEC 620A has had it’s batteries
charged for 12 to 24 hours it is ready for use. The
620A 4 only draws a little electrical power
(internal battery based) 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.
You may also have a test procedure or technical
order (T.O.) that has you inspect the calibration
sticker on the AMPTEC 620A Igniter Tester to
determine that it is still valid, or within its
calibration interval. Avoid exposing the 620A to
extreme temperatures, hot or cold which will affect
accuracy and shorten battery life-span.
A-5 Serial Number , Revision and Safety Board
Approvals
The AMPTEC 620A Igniter Tester represents the
latest in ultra-safe Igniter Tester resistance
measurements. The AMPTEC 620A-4 (serial
numbers 620A4-800 and higher) Igniter Testers
use the same main printed circuit board (PCB)
referred to as “Revision D”. This manual is
specific for the “Rev D” versions of the 620A.
Please check the Appendix of this manual for any
addendums that may apply to any differences
between the newer (Rev D.) version 620A-4s and
older (Rev C.) 620A-4 Igniter Testers with serial
numbers less than 620A4-800 (i.e. 620A4- 525).
The AMPTEC 620A-4 Igniter Tester is Mil Std
810 Method 511 Compliant for use in Explosive
Atmospheres Use to +50 degrees C . A copy of this
Approval and others is available in the password
protected section of AMPTEC RESEARCH'S
Certified for Use in Explosive Fuel Air Mixtures per
Mil Standard 810 Method 511.
A copy of this Approval and others is available in the
password protected section of AMPTEC
RESEARCH'S website www.amptec.com/tech.htm
. At present you must enter the following for access
User ID=2004 and the password=safety.
A variety of USAF Tech Orders related to the
AMPTEC 620A-4 are available there for review.
Contact AMPTEC RESEARCH if the password has
changed.

SECTION B - 620A 4 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)
20 ohm through 20Kohm ranges . . . . . . . . . . . . . . . . ±0.02% of reading ±0.02% of range
(i.e if you a using a 10.000 ohm Resistance Std. - the high limit for the 620A-4 is a ohm reading
and the low limit is ohm reading )
Temperature Range
Operating 0°C to 50°C
Storage -10°C to 70°C
Temperature Coefficient
20ohm through 20Kohm ranges ±0.002% per °C (from 0°C-15°C and 35°C-50°C)
Test Current Level
(Model 620A-4 version) 20ohm range is <5mA when operating normal, <8mA worst case when faulty
Instrument Display . . (20,000 count) 4½ digit Super Bright Light Emitting Diodes (LED)
Over-Range Indication . . . . . . . . . . . . . . . . ( select next higher range) 620A 4 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" 5.7AHr Heavy Duty) 1.2V rechargeable nickel-cadmium batteries
AC/DC Battery Charger (Option DC) provides 6VDC at 100mA nominal
Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.5" (24cm) W x 11" (27cm) D x 3"(8cm) H
Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 lbs net; 6.5 lbs shipping (not counting transit case and
accessories)
AMPTEC RESEARCH continually strives to make improvements with it's instrumentation and as such reserves the right for
general operation of its products and specifications to be subject to change on rare occasion.

C-1. Available Accessories and Options
Listed below are the options available for use with the
AMPTEC 620A Series FailSafe Ohmmeters.
Option 620-DC: 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 (Option 620-BAT)
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 (Heavy Duty) installed
in the units battery box. The batteries are held in place
by reusable tie-wraps. When ordering replacement
batteries, please specify AMPTEC option "620-BAT"
(a new set of 4 each NiCAD D cells will be supplied).
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.
Test Leads and Probes - All AMPTEC Igniter Tester
Leads and Probe sets are a minimum 48" length, (call the
Sales Department for any custom requirement).
Option “620RACK”: Rack Mount Adapter
Option "620RACK" includes an adapter tray that
allows any single 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 gold plated 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 can't reach.
Option 430 4000-ITS Mating Connector
AMPTEC offers an adapter connector that provides
equivalent circular socket connections (J9 Connector)
found on SIMPSON 4000 ITStm, and Alinco 101 series
Circuit Igniter Testers. In some applications (i.e. AIM-7
Missile harnesses) regular alligator clip leads cannot
properly connect to ( screw on ring collar type
connectors) the small recessed electrical sockets inside a
connector harness that normally mates with the J9 style
connector. This item is included in the AMPTEC 620A-
4 NSN 6625-01-460-1499NM package. The “OP430” has
the AMPTEC 620A Ohmmeter act as a 2-wire ohmmeter
from the OP430 connector out to the resistance under test.
Option "247" - Isolated Continuous Operating Power -
Allows the AMPTEC 620A series tester safely operate
continuously 24 hours a day 7 days a week. It includes an
isolated AC/DC wall adapter. This option uses a 3.0 KV
AC and DC isolated circuitry (i.e. medical grade DC to
DC convertor) to safely supply the 5.0 VDC need to
operated the units main measurement electronics
normally supply by batteries. This 3 KV medical grade
electrical isolation is the same safety isolation that cardiac
monitors use. That is they are AC line powered (i.e. 120
VAC) while electrodes are connected to a human patients'
chest. The unit’s Safety Board Approved failsafe ohmmeter
current source is still running independent of the meter’s 3.0
KV DC supply isolation circuitry. UL 61010 AC Line Isolation
Test Report confirms Isolation to 3 KV AC input protection.
Option “500” Optically Isolated Analog Output
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 measurements 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 con-
nected to "Option 500" has virtually no impact on the
620 series tester's safety.
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. Kelvin clips provide a 4 wire Kelvin Gold
plated low thermal EMF connection (minimizes the
thermocouple effect) with most connections. The
Option “300” is the recommended test lead set for
any AMPTEC 620 Series Igniter Tester for
calibration or precision measurements (i.e
AMPTEC 620ES and 620RK). 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)..