Vanguard Herculito User Manual

OPERATING INSTRUCTIONS

for the

HERCULITO

100 Amperes True DC

Digital Micro Ohm Meter

Vanguard Instruments Company

1520 S. Hellman Avenue
Ontario, California 91761

TEL: [phone] Nov 2006
FAX: [phone] Rev. 1

Herculito Operating Procedures

SAFETY SUMMARY

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.

Follow Exact Operating Procedures

Any deviation from the procedures described in this operator’s manual may create one or more
safety hazards, damage the HERCULITO, or cause errors in the test results. Vanguard
Instruments Co., Inc. assumes no liability for unsafe or improper use of the HERCULITO.
The following safety precautions must be observed during all phases of test set-up, test hookups,
testing, and test-lead disconnects.

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 HERCULITO 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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Herculito Operating Procedures

Table of Contents

1.0 INTRODUCTION ...............................................................................................................4

1.1 Applicability .....................................................................................................................4

1.2 General Description...........................................................................................................4

1.3 Functional Description......................................................................................................4

1.4 Furnished Test Accessories ...............................................................................................5

2.0 HERCULITO SPECIFICATIONS.......................................................................................6

3.0 CONTROL AND DISPLAY................................................................................................7

3.1 Herculito Front Panel ........................................................................................................7

4.0 OPERATING VOLTAGES .................................................................................................9

5.0 CABLE CONNECTION......................................................................................................9

6.0 OPERATING THE HERCULITO .....................................................................................10

6.1 Step-by-Step Procedures .................................................................................................10

6.1.1 Precautions...............................................................................................................10

6.1.2 Preparations..............................................................................................................10

6.1.3 Run Test Procedure..................................................................................................11

6.1.6 Contrast Adjustment.................................................................................................12

6.1.7 Herculito Cal Check .................................................................................................13

6.1.8 Display Previous Results..........................................................................................15

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Herculito Operating Procedures

Table of Figures

Figure 1 Herculito Current Cable...............................................................................................5

Figure 2 Herculito Front Panel...................................................................................................7

Figure 3 Herculito Connection Diagram 1..................................................................................9

Figure 4 Herculito Connection Diagram 2..................................................................................9

Figure 5 Main Menu ................................................................................................................10

Figure 6 Run Test Menu Prompts.............................................................................................11

Figure 7..Main menu .................................................................................................................11

Figure 8 Over-Range Message.................................................................................................12

Figure 9 Select Adjust Contrast Menu......................................................................................12

Figure 10 Contrast Menu .........................................................................................................12

Figure 11 Cal Check Menu ......................................................................................................13

Figure 12 Attach Short Bar Prompt..........................................................................................13

Figure 13 Calibration Connection ............................................................................................13

Figure 13 Cal Check Menus.....................................................................................................14

Figure 14 Previous Results Menu.............................................................................................15

Figure 15 Select Reading Menus..............................................................................................15

Figure 16 Test Record Readout................................................................................................15

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Herculito Operating Procedures

1.0 INTRODUCTION

1.1 Applicability

This manual applies to the Model Herculito, made by Vanguard Instruments Company.

1.2 General Description

The Herculito features microprocessor-controlled low resistance meter. The Herculito was
designed to measure very low resistances ranging from 1 micro-ohm to 300 milli-ohms with high
accuracy. The Herculito is light weight, rugged, and is easily operated by first-time users having
a minimum of training. It features one-knob control and an LCD alpha/numeric display. The
one-knob control operation is logical and simple: Turning the knob scrolls through a menu of
possible options (which display in sequence) and pressing the knob activates the selected
function. The Heculito operation is automatic, only requiring the user to connect it to an
unknown resistance and selecting the desired functions and its options. The Herculito stores the
last 3 resistance measurements, which can be displayed after a test.

1.3 Functional Description

The Herculito’s operation is based on the electrical relationships 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 flowing through the
unknown resistance is known and the voltage across the unknown resistance is read by a
precision voltmeter, the resistance read-out can be calculated using Ohm’s law.
The Herculito’s 5 Vdc test voltage is supplied by a true DC power supply. The test current is
regulated by the test load and the test cables. Test current varies slightly from 80 to 100 Ampere
depending on the resistance of the load.

Voltmeter test leads run separately 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. This feature makes possible very precise micro-ohm
measurements without having to calculate compensations for current lead resistance errors.

Note

Since the test current rise and fall time is not controlled by a current regulator circuit, precaution
should be taken to eliminate any CT sensing that might inadvertently trip Substation Bus
Differential Relays.

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Herculito Operating Procedures

1.4 Furnished Test Accessories

The Herculito is supplied with two 45-foot #8 AWG test cables with heavy-duty alligator
clamps. A Ground cable, power cord and a cable bag are also included with each Herculito.

1.5 Optional Accessories

An optional shipping case (which holds the Herculito and its cables) is also available.

Figure 1 Herculito Current Cable

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