Vanguard Instruments Company ATO-400P User manual

OPERATING INSTRUCTIONS
for the
ATO-400P and ATO-600P
10-400/600 Amperes
Digital Micro-Ohm Meters
Vanguard Instruments Company, Inc.
1710 Grevillea Court
Ontario, California 91761
TEL: [phone] May 2005
FAX: [phone] Rev. 1

ATO-400P / ATO-600P Operating Procedures
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SAFETY SUMMARY
NOTICE
This manual applies to Models ATO-400P, and ATO-600P. The operating procedures are
virtually the same for all models; any differences are clearly described in the step-by-step
procedures. Follow Exact Operating Procedures
Any deviation from the procedures described in this operator’s manual may create one or more
safety hazards, damage the ATO, or cause errors in the test results; Vanguard Instruments Co.,
Inc. assumes no liability for unsafe or improper use of the ATO.
The following safety precautions must be observed during all phases of test set-up, test hookups,
testing, and test-lead disconnects.
SAFETY WARNINGS AND CAUTIONS
This device shall be used only by trained operators.
All circuit breakers under test shall be off line and fully isolated.
Do Not Modify Test Equipment
Because of the risk of introducing unknown hazards, do not install substitute parts or perform
any unauthorized modification to any Model ATO Test Unit. To ensure that all designed safety
features are maintained, it is recommended that repairs be performed only by Vanguard
Instruments Co. factory personnel or by an authorized repair service. Unauthorized
modifications can cause serious safety hazards and will nullify the manufacturer's warranty.

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Table of Contents
1.0 INTRODUCTION ...............................................................................................................6
1.1 Applicability .....................................................................................................................6
1.2 General Description...........................................................................................................6
1.3 Functional Description......................................................................................................6
1.4 Furnished Test Accessories ...............................................................................................6
1.5 Optional Accessories.........................................................................................................7
2.0 ATO SPECIFICATIONS.....................................................................................................9
2.1 ATO-400P Specifications..................................................................................................9
2.2 ATO-600P Specifications................................................................................................10
3.0 CONTROL AND DISPLAY..............................................................................................11
3.1 ATO-400P Front Panel....................................................................................................11
3.2 ATO-600P Front Panel....................................................................................................13
4.0 IMPORTANT FEATURES...............................................................................................15
4.1 Operating Voltages..........................................................................................................15
4.2 ATO RS-232C Serial Interface.......................................................................................15
4.3 ATO USB Interface........................................................................................................15
4.4 ATO LCD Contrast Adjustment.....................................................................................15
4.5 Paper Advance or Retract...............................................................................................15
5.0 ATO PRINTER PAPER.....................................................................................................15
6.0 CABLE CONNECTION....................................................................................................16
7.0 OPERATING PROCEDURES...........................................................................................17
7.1 Step-by-Step Procedures .................................................................................................17
7.1.1 Precautions...................................................................................................................17
7.1.2 Preparations..................................................................................................................17
7.2 Operating Overview........................................................................................................17
7.2.1 Entering Alpha/Numeric Characters.............................................................................18
7.3 Run Normal Test Procedure............................................................................................21
7.4 Run Automatic Test Procedure........................................................................................25
7.5 Enter Record ID Procedure..............................................................................................28
7.6 Review Record Procedure...............................................................................................30
7.7 Restore Record Procedure...............................................................................................32
7.8 Print Test Record Directory Procedure............................................................................34
7.9 Erase Test Record Procedure...........................................................................................35
7.10 Computer Control..........................................................................................................36
7.11 Set ATO Clock Procedure.............................................................................................37
7.12 Calibration Test Procedure............................................................................................38
7.13 Diagnostic Check Procedure..........................................................................................41

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List of Figures
Figure 1 ATO Current Cable......................................................................................................7
Figure 2 ATO Sensing cable ......................................................................................................8
Figure 3 C-Clamp Cable ............................................................................................................8
Figure 4 ATO-400P Control-Panel Controls and Display.........................................................11
Figure 5 ATO-600P Control-Panel Controls and Display.........................................................13
Figure 6 ATO-400P Connection Diagram ................................................................................16
Figure 7 ATO-600P Connection Diagram ................................................................................16
Figure 8 START Menu ............................................................................................................17
Figure 9 SETUP Menu.............................................................................................................18
Figure 10 Step-by Step Procedures for ATO Operation............................................................19
Figure 11 Typical ATO-400P/600P Test Report.......................................................................24
Figure 12 Typical Directory Printout........................................................................................34
Figure 13 Calibration Test Results............................................................................................40
Figure 14 Diagnostic Test Cable Connection............................................................................42

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List of Tables
Table 1.0 ATO-400P Specifications...........................................................................................9
Table 2.0 ATO-600P Specifications.........................................................................................10
Table 3.0 Functional Description of ATO-400P Controls and Display......................................12
Table 4.0 Functional Description of ATO-600P Controls and Display......................................14
Table 5.0 Run Test Procedure (Measure an Unknown Resistance) ...........................................21
Table 6.0 Run Automatic Test Procedure (Measure an Unknown Resistance)..........................25
Table 7.0 Enter Record ID Procedure (test-record, site, and equipment identification) .............28
Table 8.0 Review Record Procedure ........................................................................................30
Table 9.0 Restore Record Procedure ........................................................................................32
Table 10.0 Print Test Record Directory Procedure ...................................................................34
Table 11.0 Erase Test Record Procedure..................................................................................35
Table 12.0 Set ATO Real Time Clock Procedure.....................................................................37
Table 13.0 Calibration Test Procedure .....................................................................................38
Table 14.0 Diagnostic Check Procedure...................................................................................41

ATO-400P / ATO-600P Operating Procedures
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1.0 INTRODUCTION
1.1 Applicability
This manual applies to the Model ATO-400P™ and Model ATO-600P™ (hereafter, ATO),
made by Vanguard Instruments Company, Inc.
1.2 General Description
The ATO-400P/600P are third generation micro-ohmmeters made by Vanguard Instruments
Company. The ATO-400P/600P feature high accuracy microprocessor-controlled measurement
of very low resistances, ranging from 1 micro-ohm to 300 milli-ohms. The ATO is field-
portable, rugged, and is easily operated by first-time users having a minimum of training. It
features a 16-key push button pad for entering test parameters and control functions and a 4-line
by 20-character LCD alpha/numeric readout for displaying control-option menus, measured
resistance values, and related data. The ATO has a built-in thermal printer, which prints test data
on 2.5-inch-wide thermal sensitive paper. The operation requires little more than connecting test
leads to an unknown resistance and selecting the desired functions and its options. Operators
select the test current (10 to 400 amperes for ATO-400P or 10 to 600 amperes for ATO-600P)
and test time (5 to 60 seconds). Measured resistance data is displayed and can be printed on the
thermal printer. The measured resistance data can also be stored (up to 63 records of 96 readings
each) in FLASH EEPROM memory. Operators can recall the stored resistance measurements
and related data at a later time for review, printing or down loading to the PC. Down loading test
records is accomplished by using the ATO’s built-in RS-232C or USB ports.
1.3 Functional Description
The ATO’s operation is based on the electrical relationship described by Ohm’s law: R=V/I,
where I is a known current and V is the dc voltage measured across the unknown resistance
(typically, a circuit breaker’s contacts). Since the current (user selected) through the unknown
resistance is known and the voltage across the unknown resistance is measured by a precision
voltmeter, the resistance read-out can be calculated using Ohm’s law. The ATO test voltage is
supplied by an unfiltered DC power supply. A regulated constant-current source outputs the
preset current selected by the user.
The DC test current is selectable from 10 to 400 amperes for the ATO-400P and from 10 to 600
amperes for ATO-600P. Since the ATO-400P and ATO-600P use unfiltered DC current
supplies, there is the possibility of inductively tripping a circuit breaker bus differential relay.
Each ATO is supplied with a set of current cables and voltage sensing cables. Voltage sensing
test leads are separate from the current-bearing test leads to the resistive load; thus, voltages are
measured at the terminals of the resistance being tested, eliminating any I•R voltage drop error in
the current cables. These ATO features make very precise micro-ohm measurements possible
without having to compensate for current-lead-resistances errors.
1.4 Furnished Test Accessories
The ATO is supplied with two 15-foot (#1/0 AWG) test cables with heavy-duty alligator clamps
and two 15-foot voltage-sensing cables with alligator clamps. A ground cable and power cord is
included with each ATO.

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1.5 Optional Accessories
1. Heavy-duty welding-type C-clamps (Figure 3) are available as optional accessories. These C-
clamps allow test lead connections to a wide variety of bushing sizes, bus bars, and
conductors that require low-resistance test-lead contacts.
2. An optional shipping case (which holds the ATO and its cables) is also available.
Figure 1 ATO Current Cable

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Figure 2 ATO Sensing cable
Figure 3 C-Clamp Cable

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2.0 ATO SPECIFICATIONS
2.1 ATO-400P Specifications
ATO-400P specifications and leading particulars are listed in Table 1.0
Table 1.0 ATO-400P Specifications
MODEL.......................ATO-400P
TYPE............................Special-Purpose Test Equipment, Portable, Low Resistance-Ohmmeter
CONFIGURATION......Third-generation (improved design, superseding original model)
SIZE (inches)..............16.8 Wide by 12.6 High by 10.6 Deep (42.7 Cm x 32 Cm x 30.5 Cm)
WEIGHT.......................43 pounds (19.5 Kg)
TEST CURRENT
RANGE ........................10 Amperes to 400 Amperes, selectable in 1 ampere steps
RESISTANCE
RANGE ........................1 micro-ohm to 300 milli-ohms
ACCURACY................± 1 % Reading, ± 1 Count
MEMORY.....................63 records of 96 reading each
DISPLAY......................Backlit LCD, 4-lines high by 20 characters wide
CONTROL...................Keypad: 10 number keys and 6 function keys
PRINTER .....................Thermal printer, 2.5-inch wide thermal paper
INPUT POWER...........20 amps, 90-230 Vac, 50/60 Hz, with built in 25A circuit breaker
UNIT PROTECTION...Thermal-overload sensor and cutoff
INTERFACE................RS-232C and USB Ports for PC Interface
ENVIRONMENT..........Operating: -10°C to 50°C (15?F to 122?F)
......................................Storage: -30°C to 70°C (-22?F to 158?F)
FURNISHED ITEMS...One power cord, one ground cable, 15-ft.(#1/0 AWG) current test lead
......................................cables, 15-ft. sensing test lead cables
EXPENDABLES.........Paper, Thermal sensitive, 2.5-inch wide roll (VIC p/n TP3)
WARRANTY................One-Year Parts & Labor (Post-Warranty Service Contracts Available)
ATO-400P SPECIFICATIONS ARE SUBJECT TO UPGRADES AND MAY BE CHANGED WITHOUT PRIOR NOTICE.

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2.2 ATO-600P Specifications
ATO-600P specifications and leading particulars are listed in Table 2.0
Table 2.0 ATO-600P Specifications
MODEL.......................ATO-600P
TYPE............................Special-Purpose Test Equipment, Portable, Low Resistance-Ohmmeter
CONFIGURATION......Third-generation (improved design, superseding original model)
SIZE (inches)..............16.8 Wide by 12.6 High by 10.6 Deep (42.7 Cm x 32 Cm x 30.5 Cm)
WEIGHT.......................43 pounds (19.5 Kg)
TEST CURRENT
RANGE ........................10 Amperes to 600 Amperes, selectable in 1 ampere steps
RESISTANCE
RANGE ........................1 micro-ohm to 300 milli-ohms
ACCURACY................± 1 % Reading, ± 1 Count
MEMORY.....................63 records of 96 reading each
DISPLAY......................Backlit LCD, 4-lines high by 20 characters wide
CONTROL...................Keypad: 10 number keys and 6 function keys
PRINTER .....................Thermal printer, 2.5-inch wide thermal paper
INPUT POWER...........20 amps, 90-230 Vac, 50/60 Hz, with built in 25A circuit breaker
UNIT PROTECTION...Thermal-overload sensor and cutoff
INTERFACE................RS-232C and USB Ports for PC Interface
ENVIRONMENT..........Operating: -10°C to 50°C (15?F to 122?F)
......................................Storage: -30°C to 70°C (-22?F to 158?F)
FURNISHED ITEMS...One power cord, one ground cable, 15-ft. (#1/0 AWG) current test lead
......................................cables, 15-ft. sensing test lead cables
EXPENDABLES.........Paper, Thermal sensitive, 2.5-inch wide roll (VIC p/n TP3)
WARRANTY................One-Year Parts & Labor (Post-Warranty Service Contracts Available)
ATO-600P SPECIFICATIONS ARE SUBJECT TO UPGRADES AND MAY BE CHANGED WITHOUT PRIOR NOTICE.

ATO-400P / ATO-600P Operating Procedures
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3.0 CONTROL AND DISPLAY
3.1 ATO-400P Front Panel
The ATO-400P controls and displays are shown in the control-panel illustration, Figure 4.
Pointing leader lines reference each item with an index number. Each index number is cross-
referenced to a functional description in Table 3, which describes the function and purpose of
each item on the control panel. Although the purpose of these controls and the display may seem
obvious and intuitive, users should become familiar with them before attempting to use the
ATO-400P. First-time users should also review and become familiar with the Safety Summary
on the front page.
Figure 4 ATO-400P Control-Panel Controls and Display

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Table 3.0 Functional Description of ATO-400P Controls and Display
Figure 1
Index # Adjacent Panel Marking Functional Description
1 & 13 (Wing Nut) Current lead connectors.
2USB USB connector. USB port is for factory
calibration, firmware updates, and interfacing
with the software program supplied with each
ATO.
3RS-232C RS-232C interface port; 9-pin connector;
female DB type. The data are set to 115,200
baud, 1 start bit, 8 data bits, and no parity bit;
PIN ...............SIGNAL
2 Rx
3 Tx
5 Signal Gnd
This serial port is for factory calibration,
firmware updates, and interfacing with the
software program supplied with each ATO.
4HIGH CURRENT
PRESENT LED indicator, red; Lights when test current is flowing through the current test leads.
5No Marking Input power connector with third-wire safety
ground.
6GROUND
(Wing Nut) ATO-400P ground stud. Connect ground stud to substation ground using provided cable.
7No Marking Circuit breaker, 25A.
8No marking Built-in thermal printer, prints test result data
on 2.5-inch-wide thermal paper.
9No marking LCD; 4-line by 20-character; back-lighted;
displays menus of selections, operator entries,
and test-measurement results.
10 No marking Operating key-pad controls, 10 alpha-numeric
keys and 6 function keys (START, STOP,
CLEAR, ENTER, & CONTRAST/PAPER
positioning ?& ?).
11 & 12 (Resistor Symbol) Voltage-sensing connector jacks (red).

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3.2 ATO-600P Front Panel
The ATO-600P controls and displays are shown in the control-panel illustration, Figure 5.
Pointing leader lines reference each item with an index number. Each index number is cross-
referenced to a functional description in Table 4, which describes the function and purpose of
each item on the control panel. Although the purpose of these controls and the display may seem
obvious and intuitive, users should become familiar with them before attempting to use the
ATO-600P. First-time users should also review and become familiar with the Safety Summary
on the front page.
Figure 5 ATO-600P Control-Panel Controls and Display

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Table 4.0 Functional Description of ATO-600P Controls and Display
Figure 1
Index # Adjacent Panel Marking Functional Description
1 & 13 (Wing Nut) Current lead connectors.
2USB USB connector. USB port is for factory
calibration, firmware updates and interfacing
with the software program supplied with each
ATO.
3RS-232C RS-232C interface port; 9-pin connector;
female DB type. The data are set to 115,200
baud, 1 start bit, 8 data bits, and no parity bit;
PIN ...............SIGNAL
2 Rx
3 Tx
5 Signal Gnd
This serial port is for factory calibration,
firmware updates, and interfacing with the
software program supplied with each ATO.
4HIGH CURRENT
PRESENT LED indicator, red; Lights when test current is flowing through the current test leads.
5No Marking Input power connector with third-wire safety
ground.
6GROUND
(Wing Nut) ATO-600P ground stud. Connect ground stud to substation ground using provided cable.
7No Marking Circuit breaker, 25A.
8No marking Built-in thermal printer, prints test result data
on 2.5-inch-wide thermal paper.
9No marking LCD; 4-line by 20-character; back-lighted;
displays menus of selections, operator entries,
and test-measurement results.
10 No marking Operating key-pad controls, 10 alpha-numeric
keys and 6 function keys (START, STOP,
CLEAR, ENTER, & CONTRAST/PAPER
positioning ?& ?).
11 & 12 (Resistor Symbol) Voltage-sensing connector jacks (red).

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4.0 IMPORTANT FEATURES
4.1 Operating Voltages
The ATO operates with voltages between 90-240Vac, 50/60Hz.
4.2 ATO RS-232C Serial Interface
A built-in, RS-232C port permits the ATO to be interfaced with an IBM-compatible personal
computer. An IBM PC software package supplied with each ATO allows the user to retrieve test
records stored in the ATO’s memory. The software is compatible with Windows XP.
The RS-232C port is also used to calibrate the ATO at the factory.
4.3 ATO USB Interface
A built-in, USB port permits the ATO to be interfaced with an IBM-compatible personal computer.
An IBM PC software package supplied with each ATO allows the user to retrieve test records stored
in the ATO’s memory. The software is compatible with Windows XP.
The USB port is also used to calibrate the ATO at the factory.
4.4 ATO LCD Contrast Adjustment
The purpose of this procedure is to adjust the contrast level of the alpha-numeric characters
shown on the LCD, in order to produce the best readability for the ambient light in the testing
area. To darken the LCD contrast, press and hold the Contrast/Paper ?key for more than 1
second. To lighten the LCD contrast, press and hold the Contrast/Paper ?key for more than 1
second. Release key when desired contrast level is obtained. The ATO saves this LCD contrast
setting level in memory.
4.5 Paper Advance or Retract
To advance the thermal paper, press and release the Contrast/Paper ?key. The thermal paper
will be advanced by 1/2 inch. To retract the thermal paper, press and release the Contrast/Paper ?
key. The thermal paper will be retracted by 1/2 inch.
5.0 ATO PRINTER PAPER
The ATO printer uses 2.5-inch wide thermal paper for printing test results. In order to maintain
the highest quality printing and to avoid paper jams, we recommend using the paper supplied by
our factory. Paper can be ordered from the following two sources:
Vanguard Instruments Co, Inc.
1710 Grevillea Court
Ontario, CA 91761
Tel: [phone]
Fax: [phone]
Part Number: TP-3 Paper
BG Instrument Co.
Route 1, Box 258
Mead, WA 99201
Tel: [phone]
Fax: [phone]
Part Number: TP-3 paper

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6.0 CABLE CONNECTION
The ATO is supplied with 15-foot (#1/0 AWG) current-carrying cables and 15-foot voltage-
sensing cables. Both cables are terminated with heavy-duty alligator clamps to connect to the
device being tested. A typical cable connection for the ATO to a device under test is shown in
figure 6 and figure 7. To protect the ATO against static discharge in the substation, always
connect the unit’s ground stud to the substation ground. It is also highly recommended to ground
one side of the circuit breaker bushing during testing to eliminate any static discharge through
the ATO.
NOTE
The sense input is not polarity sensitive. The sense cables may be
connected to either input without affecting circuit operation.
Figure 6 ATO-400P Connection Diagram
Figure 7 ATO-600P Connection Diagram

ATO-400P / ATO-600P Operating Procedures
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7.0 OPERATING PROCEDURES
Review Figure 10 before proceeding with the step-by-step procedures that follow.
7.1 Step-by-Step Procedures
7.1.1 Precautions
Do not measure the resistance of inductive devices. This can generate unsafe high-voltage spikes
(created by a collapsing magnetic field) if the test current is interrupted by detaching a test lead
during a test. Do not touch or disconnect any test lead that is connected to a device under test
while current is being conducted. Failure to heed this warning can cause injury to the user
and or damage to the ATO. The ATO measures low, non-inductive resistances (e.g., breaker
contacts and bus-bar junctions). If the resistance of an inductive device needs to be measured,
then the use of an instrument designed for that purpose is recommended (such as the WRM made
by Vanguard Instruments Company).
7.1.2 Preparations
a. Ground the ATO to Substation ground.
b. Plug the ATO power cable into a power outlet.
c. Connect the current-cable lugs and the voltage-sensing cable plugs to control-panel (Figures 4
& 5).
d. Attach the current test-cable clamps to opposite terminals of the resistive load being tested
(Figures 6 & 7).
e. Attach the voltage-sensing clamps to the terminals of the resistive load. The sensing voltage
clamps should be inside the current clamps.
f. Turn on ATO power, by pressing the rocker switch to ON.
7.2 Operating Overview
Procedures for operating the ATO are presented in tabular format, with a different table for each
of the operations available. All operations are described in step-by-step sequences. Each step is
indexed by number and indicates an operator action, followed by a description of what should be
observed on the ATO display to confirm the action. All operations begin with the START menu
(shown below):
Figure 8 START Menu
Item 1 (RUN TEST) is a menu of functions and options available for measuring an unknown
resistance. Item 2 (SETUP) is for record manipulation in the ATO. Item 2 (SETUP) expands
into a menu of support functions. Item 3 (DIAGNOSTIC) is a performance-verification
operation for checking key circuit functions.
1. RUN
TEST 05/30/05
2. SETUP 12:25:00
3. DIAGNOSTIC

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Figure 9 SETUP Menu
The SETUP MENU lists four user options:
Item 1 (ENTER ID) is used to input identification information for each stored data record (see
7.1.7).
Item 2 (REVIEW RECORD) is used to review stored records (see 7.1.8).
Item 3 (RESTORE RECORD) is used to erase or restore test records or to print a directory of test
records in stored memory (see 7.1.9).
Item 4 (NEXT PAGE) is used to set the ATO’s real time clock and perform a calibration test.
7.2.1 Entering Alpha/Numeric Characters
Entering alpha/numeric characters is done via the keypad (similar to a telephone keypad – see
item 9 of Figures 4 & 5). To input characters, press the key once to select the number marked on
the key. Press the key a second time to select the first letter marked on the key. Press the key a
third time to select the second letter marked on the key. Press the key a fourth time to select the
third letter marked on the key.
Additional key presses will repeat the selection cycle (e.g., 2, A, B, C, 2 . . .).
When the character of choice is selected, press the ?key to advance to next character space;
Press the ?key to go back one character space. Press CLEAR to delete a selected character (the
cursor must be under the character to be deleted).
Again, press the “ENTER” key to load all character selections and move the next input screen.
If no information is needed in a particular input screen, press the “ENTER” key and the display
will advance to the next screen without entering any data.
1. ENTER RECORD ID
2. REVIEW RECORD
3. RESTORE RECORD
4. NEXT PAGE

ATO-400P / ATO-600P Operating Procedures
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Figure 10 Step-by Step Procedures for ATO Operation

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