Electrical Engineering Centre

Introduction

This equipment is used to measure the resistance ( ohm) of the earth.It is important to ensure that the electrical installation grounding system in accordance with the specifications and meet the earthing requirement.

First we must know about Earth Resistance Tester specification.

Measurement Ranges  :

• Earth Resistance : 0 – 20W /0 – 200W /0 – 2000W

• Earth Voltage : (50Hz, 60Hz) 0 – 200V AC

Overload Protection :

• Earth Resistance : 200V AC 10 seconds (across two of the three terminals)

• Earth Voltage : 300V AC for 1 minute

Accuracy :

• Earth Resistance
  ±2%rdg ±0.1W (20W range)
  ±2%rdg ±3dgt (200W /2000W range)

• Earth Voltage : ±1%rdg ±4dgt

Safety Standard :

• IEC1010-1 CAT.III

Withstand Voltage

• 3700V AC for 1 minute

Power Source :

• R6P (AA) x 6

Accessories :

• Model/Part No.7095 (Test Leads) x 1set.

• Model/Part No.8032 (Auxiliary earth spikes) x 1set.
• Model/Part No.7094 (Simplified measurement probe) x 1set.
• R6P (AA) x 6 batteries.
• Model/Part No.9084 Carrying Case.
• Neck Strap.
• Instruction Manual.

Features :

• Dust and drip proof. (designed to IEC 529 IP54)
• In addition to the facility for precision measurement, test leads for simplified two wire measuring system also supplied as standard accessories. (unit can be hung from the neck for simplified measurement)
• Designed to meet IEC1010-1 safety standard
• Automatic warning when resistance of auxiliary earth spikes is in excess of tolerance
• 2mA measuring current permits earth resistance tests without tripping earth leakage current breakers in the circuit under test.

Layout Diagram

1) LCD DISPLAY

2) INDICATOR LED

3) PRESS TO TEST BUTTON

4) RANGE SELECTOR SWITCH

Principle of Measurement

This instrument makes earth resistance measurement with fall-of potential method, which is a method to obtain earth resistance value Rx by applying AC constant current I between the measurement object E (earth electrode) and C (current electrode), and finding out the potential difference V between E and P (potential electrode).

Rx = V / I

How to perform the earth test?

I will explain more detail about How to perform Earth resistance Measurement and the right technique.

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