Vanguard Instruments Auto-Ohm 200 S3 User manual

Auto-Ohm 200 S3 / DMOM-200 S3 / DMOM-600
True DC Digital Micro-Ohmmeters
USER’S MANUAL
Vanguard Instruments Company, Inc.
1520 S. Hellman Ave.
Ontario, California 91761, USA
TEL: [phone]
FAX: [phone]
August 2019
Revision 2.4

Auto-Ohm 200 S3 / DMOM-200 S3 / DMOM-600 USER’S MANUAL REV 2
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SAFETY SUMMARY
This manual applies to the Auto-Ohm 200 S3, the DMOM-200 S3, and the DMOM-600 digital micro-ohmmeters.
The operating procedures are virtually the same for all three models, and any differences are clearly described
where applicable.
FOLLOW EXACT OPERATING PROCEDURES
Any deviation from the procedures described in this user’s manual may create one or more safety hazards,
damage the Auto-Ohm 200 S3/DMOM-200 S3/DMOM-600, or cause errors in the test results. Vanguard
Instruments Co., Inc. assumes no liability for unsafe or improper use of the Auto-Ohm 200 S3/DMOM-200
S3/DMOM-600. The following safety precautions must be observed during all phases of test setup, test hookups,
testing, and test lead disconnection.
SAFETY WARNINGS AND CAUTIONS
The Auto-Ohm 200 S3/DMOM-200 S3/DMOM-600 shall be used only by trained operators. All circuit breakers
under test shall be off-line and fully isolated.
SERVICE AND REPAIR
•Do not install substitute parts or perform any unauthorized modification to any Auto-Ohm 200 S3/DMOM-200
S3/DMOM-600 test unit.
•Repairs must be performed only by Vanguard Instruments Company factory personnel or by an authorized
repair service provider. Unauthorized modifications can cause safety hazards and will void the manufacturer’s
warranty.
EQUIPMENT RATINGS
IP Rating: The enclosures for Auto-Ohm 200 S3, DMOM-200 S3, and DMOM-600 have an IP rating of 32.
Pollution Degree: The Auto-Ohm 200 S3, DMOM-200 S3, and DMOM-600 have a pollution rating of 2.
Operating Voltage: The Auto-Ohm 200 S3, DMOM-200 S3, and DMOM-600 are rated for use with an operating
voltage of 120V or 240V, auto-ranging ±10% of selected voltage.
Power Cord: The Auto-Ohm 200 S3, DMOM-200 S3, and DMOM-600 are supplied with a 16 AWG, 16A power cord
with a NEMA 5-15P plug. Replacement cable shall have the same or better rating and is available through the
manufacturer.
VENTILATION REQUIREMENTS
The Auto-Ohm 200 S3, DMOM-200 S3, and DMOM-600 must be operated with the enclosure lid open.
SAFETY SYMBOLS
Indicates that caution should be exercised
Indicates location of chassis ground terminal
CLEANING
To clean the Auto-Ohm 200 S3, DMOM-200 S3, and DMOM-600:
•Disconnect all cables and turn the unit off.
•Use a soft, lint-free cloth to wipe all surfaces clean.
•Avoid getting moisture in openings and connectors.
•Don't use any cleaning products or compressed air.

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TABLE OF CONTENTS
CONVENTIONS USED IN THIS DOCUMENT ....................................................................... 4
1.0 INTRODUCTION.................................................................................................................... 5
1.1 Auto-Ohm 200 S3 General Description and Features ..................................................... 5
1.2 DMOM-200 S3 General Description and Features .......................................................... 7
1.3 DMOM-600 General Description and Features............................................................... 9
1.4 Cables and Accessories .................................................................................................... 9
1.5Auto-Ohm 200 S3 Technical Specifications ................................................................... 12
1.6 DMOM-200 S3 Technical Specifications ........................................................................ 13
1.7 DMOM-600 Technical Specifications............................................................................. 14
1.8 Auto-Ohm 200 S3 Controls and Indicators .................................................................... 15
1.9 DMOM-200 S3 Controls and Indicators......................................................................... 16
1.10 DMOM-600 Controls and Indicators.............................................................................. 17
2.0 PRE-TEST SETUP ................................................................................................................. 18
2.1 Operating Voltages ........................................................................................................ 18
2.2 LCD Screen Contrast Control.......................................................................................... 18
3.0 OPERATING PROCEDURES ................................................................................................. 19
3.1 Connection Diagrams..................................................................................................... 19
3.3 Setting the Interface Language...................................................................................... 21
3.4 Testing Procedures ........................................................................................................ 22
3.4.1. Entering Test Record Header Information ............................................................. 22
3.4.2. Performing a Test ................................................................................................... 25
3.4.3. Performing a Quick Test ......................................................................................... 36
3.5 Working With Test Records ........................................................................................... 40
3.5.1. Viewing the Contents of the Working Memory..................................................... 40
3.5.2. Saving Test Results to a Test Record...................................................................... 42
3.5.3. Restoring a Test Record From Flash EEPROM........................................................ 44
3.5.4. Restoring a Test Record From a USB Flash Drive ................................................... 48
3.5.5. Copying Test Records to a USB Flash Drive............................................................ 51
3.5.6. Viewing the Test Record Directory......................................................................... 54
3.5.7. Erasing Test Records from the Flash EEPROM ....................................................... 56
3.5.8. Erasing Test Records from a USB Flash Drive......................................................... 61
4.0 Getting the Latest Firmware, Software, and Manuals....................................................... 64

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LIST OF TABLES
Table 1. Auto-Ohm 200 S3 Technical Specifications..................................................................... 12
Table 2. DMOM-200 S3 Technical Specifications ......................................................................... 13
Table 3. DMOM-600 Technical Specifications .............................................................................. 14
LIST OF FIGURES
Figure 1. Furnished Current and Sense Combination Cables ....................................................... 10
Figure 2. Furnished Current Cable and Sense Cables for DMOM-600 ......................................... 10
Figure 3. Optional Cable with C-Clamp......................................................................................... 11
Figure 4. Optional Hand Spike ...................................................................................................... 11
Figure 5. Auto-Ohm 200 S3 Controls and Indicators .................................................................... 15
Figure 6. DMOM-200 S3 Controls and Indicators......................................................................... 16
Figure 7. DMOM-600 Controls and Indicators.............................................................................. 17
Figure 8. Typical Auto-Ohm S3 Connection Diagram ................................................................... 19
Figure 9. Typical Auto-Ohm S3 Connection Diagram with Dual Ground Option.......................... 19
Figure 10. Sample DMOM-200 S3/DMOM-600 Printout.............................................................. 35
Figure 11. Sample DMOM-200 S3/DMOM-600 Printout (with Dual Ground Option) ................. 35

Auto-Ohm 200 S3 / DMOM-200 S3 / DMOM-600 USER’S MANUAL REV 2
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CONVENTIONS USED IN THIS DOCUMENT
This document uses the following conventions:
•The general term “Auto-Ohm S3” is used in this manual to refer to the Auto-Ohm 200 S3,
the DMOM-200 S3, and the DMOM-600.
•A key, switch, or knob on the Auto-Ohm S3 is indicated as [KEY], [SWITCH], [KNOB].
•Menu names are referenced as “MENU NAME”
•Auto-Ohm S3 screen output is shown as:
•When instructions are provided, the menu item that should be selected is outlined with a
rectangle as shown below (option 3 should be selected):
•Warning messages are indicated as:
WARNING
Warning message
•Important notes are indicated as:
NOTE
Note details
 
 
 
 
 


 
 
 
 
 



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1.0 INTRODUCTION
1.1 Auto-Ohm 200 S3 General Description and Features
The Auto-Ohm-200 S3 is Vanguard’s fourth generation, microprocessor-based, true DC
micro-ohmmeter. It is designed for testing EHV circuit-breaker contact resistances, bushing
contact joints, welding joints, or for any low-resistance measuring application. This high current
and very lightweight (16.8 lbs/ 7.6 Kg) micro-ohmmeter is designed to meet the IEEE
C57.09-1999 (5.15) requirement for testing circuit breaker contact resistance.
The Auto-Ohm-200 S3 can accurately measure resistance values from 1 micro-ohm to 5 ohms. A
0.1 micro-ohm resolution is possible with current greater than 5A. The Auto-Ohm-200 S3
applies a selectable true DC test current from 1A to 200A to the resistance load to be tested.
The Auto-Ohm-200 S3 controls the test current’s rise and fall rates. The test current rise and fall
rate can be selected from 5 seconds to 10 seconds. An “Auto Test” mode is also available and
can be initiated simply by applying the sense cables’ leads across the two points of interest in
the current path. This feature is very convenient when measuring a sequence of several
resistance values in a circuit breaker contact. The Auto-Ohm 200 S3 can also compare test
results against preset limits and determine if a test passed or failed, and a “Pass” or “Fail” flag is
displayed accordingly.
Since a true DC current (with controlled rise/fall time) is passed through the circuit breaker
contact, no magnetic transient is induced into the breaker’s current transformers. This feature
greatly reduces the risk of inductively trip-ping a breaker control (bus differential relay).
With the Dual Ground option, the Auto-Ohm-200 S3 can also measure the circuit breaker
contact resistance with both sides of the breaker bushing being grounded. When a test current
is applied to a circuit breaker with both sides grounded, some of the test current flows through
the safety ground cables. Using an external current sensor, the Auto-Ohm-200 S3 measures and
eliminates this current from the total test current. The Auto-Ohm then calculates the actual
resistance value of the circuit breaker.
The Auto-Ohm-200 S3 features a back-lit 128 x 64 pixel LCD screen that is viewable in both
direct sunlight and low-light levels. The resistance readings are displayed on the LCD screen in
micro-ohms or milliohms. The unit is operated via a convenient 44-key “QWERTY” keypad on
the front panel. The Auto-Ohm 200 S3 can store 128 records of 64 readings internally, and up to
999 test records on an external USB Flash drive. Test header information (Company, Substation,
circuit breaker ID’s) can also be entered using the 44-key keypad and is stored with each test
record.
Windows® based (XP/Vista/7) analysis software is provided with each unit and can be used to
remotely control the Auto-Ohm 200 S3 via the RS-232C port. Using this software, the user can
retrieve test records (from the unit’s memory or a USB Flash drive), analyze test results, and
print test results on a desktop printer. Test records can also be exported to PDF, Excel, and XML
formats.

Auto-Ohm 200 S3 / DMOM-200 S3 / DMOM-600 USER’S MANUAL REV 2
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The Auto-Ohm-200 S3 is furnished with a 30-ft test (#1 AWG) cable set. A 15-ft test cable set is
also available as an option. Test cables are terminated with heavy duty welding type clamps.
The test current and voltage sense cables are isolated and fastened to the clamp jaws. This
feature allows for a simple connection to the circuit breaker bushing. An optional voltage sense
cable and probe can be used to measure resist-ance in small access locations. Optional
heavy-duty, welding type C-clamps are also available allowing the user to connect the test leads
to a wide variety of bushing sizes, bus-bars, or large conductors.

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1.2 DMOM-200 S3 General Description and Features
The DMOM-200 S3 is Vanguard’s fourth generation, microprocessor-based, true DC micro-
ohmmeter. It is designed for testing EHV circuit-breaker contact resistances, bushing contact
joints, welding joints, or for any low-resistance measuring application. This high current and
very lightweight (19.8 lbs/ 8.9 Kg) micro-ohmmeter is designed to meet the IEEE C57.09-1999
(5.15) requirement for testing circuit breaker contact resistance.
The DMOM-200 S3 can accurately measure resistance values from 1 micro-ohm to 5 ohms. A
0.1 micro-ohm resolution is possible with current greater than 5A. The DMOM-200 S3 applies a
selectable true DC test current from 1A to 200A to the resistance load to be tested. The
DMOM-200 S3 controls the test current’s rise and fall rates. The test current rise and fall rate
can be selected from 5 seconds to 10 seconds. An “Auto Test” mode is also available and can be
initiated simply by applying the sense cables’ leads across the two points of interest in the
current path. This feature is very convenient when measuring a sequence of several resistance
values in a circuit breaker contact. The DMOM-200 S3 can also compare test results against
preset limits and determine if a test passed or failed, and a “Pass” or “Fail” flag is displayed
accordingly.
Since a true DC current (with controlled rise/fall time) is passed through the circuit breaker
contact, no magnetic transient is induced into the breaker’s current transformers. This feature
greatly reduces the risk of inductively tripping a breaker control (bus differential relay).
With the Dual Ground option, the DMOM-200 S3 can also measure the circuit breaker contact
resistance with both sides of the breaker bushing being grounded. When a test current is
applied to a circuit breaker with both sides grounded, some of the test current flows through
the safety ground cables. Using an external current sensor, the DMOM-200 S3 measures and
eliminates this current from the total test current. The DMOM-200 S3 then calculates the actual
resistance value of the circuit breaker.
The DMOM-200 S3 features a back-lit 128 x 64 pixel LCD screen that is viewable in both direct
sunlight and low light levels. The resistance readings are displayed on the LCD screen in micro-
ohms or milliohms. The unit is operated via a convenient 44-key “QWERTY” keypad on the front
panel. The DMOM-200 S3 can store 128 records of 64 readings internally, and up 999 test
records on an external USB Flash drive. Test header information (Company, Substation, circuit
breaker ID’s) can also be entered using the 44-key keypad and is stored with each test record.
The DMOM-200 S3 also features a built-in 2.5” wide thermal printer that can be used to print
test reports in the field.
Windows® based (XP/Vista/7) analysis software is provided with each unit and can be used to
remotely control the DMOM-200 S3 via the RS-232C port. Using this software, the user can
retrieve test records (from the unit’s memory or a USB Flash drive), analyze test results, and
print test results on a desktop printer. Test results can also be exported to PDF, Excel, and XML
formats.

Auto-Ohm 200 S3 / DMOM-200 S3 / DMOM-600 USER’S MANUAL REV 2
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The DMOM-200 S3 is furnished with a 30-ft test cable set. A 15-ft test cable set is also available
as an option. Test cables are terminated with heavy duty welding type clamps. The test current
and voltage sense cables are isolated and fastened to the clamp jaws. This feature allows for a
simple connection to the circuit breaker bushing. An optional voltage sense cable and probe
can be used to measure resistance in small access locations. Optional heavy-duty, welding type
C-clamps are also available allowing the user to connect the test leads to a wide variety of
bushing sizes, bus-bars, or large conductors.

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1.3 DMOM-600 General Description and Features
The DMOM-600 is specifically designed for testing EHV circuit-breaker contact resistances,
bushing contact joints, welding joints, or for any low-resistance measuring application. This high
current and very lightweight (33 lbs/ 15 Kg) micro-ohmmeter is designed to meet the IEEE
C57.09-1999 (5.15) requirement for testing circuit breaker contact resistance.
The DMOM-600 can accurately measure resistance values from 1 micro-ohm to 450 milliohms.
A 0.1 micro-ohm resolution is possible with current greater than 10A. The DMOM-600 applies a
selectable true DC test current from 10A to 600A to the resistance load to be tested. The
DMOM-600 controls the test current’s rise and fall rates. The test current rise and fall rate can
be selected from 5 seconds to 10 seconds. An “Auto Test” mode is also available and can be
initiated simply by applying the sense cables’ leads across the two points of interest in the
current path. This feature is very convenient when measuring a sequence of several resistance
values in a circuit breaker contact. The DMOM-600 can also compare test results against preset
limits and determine if a test passed or failed, and a “Pass” or “Fail” flag is displayed
accordingly.
Since a true DC current (with controlled rise/fall time) is passed through the circuit breaker
contact, no magnetic transient is induced into the breaker’s current transformers. This feature
greatly reduces the risk of inductively tripping a breaker control (bus differential relay).
With the Dual Ground option, the DMOM-600 can also measure the circuit breaker contact
resistance with both sides of the breaker bushing being grounded. When a test current is
applied to a circuit breaker with both sides grounded, some of the test current flows through
the safety ground cables. Using an external current sensor, the DMOM-600 measures and
eliminates this current from the total test current. It then calculates the actual resistance value
of the circuit breaker.
The DMOM-600 features a back-lit 128 x 64 pixel LCD screen that is viewable in both direct
sunlight and low light levels. The resistance readings are displayed in a large font on the LCD
screen in micro-ohms or milliohms. The unit is operated via a convenient 44-key “QWERTY”
keypad on the front panel. The DMOM-600 can store 128 records of 64 readings internally, and
up 999 test records on an external USB Flash drive. Test header information (Company,
Substation, circuit breaker ID’s) can also be entered using the 44-key keypad and is stored with
each test record. The DMOM-600 also features a built-in 2.5” wide thermal printer that can be
used to print test reports in the field.
Windows® based (XP/Vista/7) analysis software is provided with each unit. Using this software,
the user can retrieve test records (from the unit’s memory or a USB Flash drive), analyze test
results, and print test results on a desktop printer. Test results can also be exported to PDF,
Excel, and XML formats.
The DMOM-600 is furnished with a 15-ft (#1/0 AWG) test cable set. Custom test cable lengths
are optionally available. Optional heavy-duty, welding type C-clamps are also available allowing
the user to connect the test leads to a wide variety of bushing sizes, bus-bars, or large
conductors.
1.4 Cables and Accessories