User’s Manual Ground Resistance Clamp On Tester MODEL 382356 WARRANTY EXTECH INSTRUMENTS CORPORATION warrants the basic instrument to be free of defects in parts and workmanship for one year from date of shipment (a six month limited warranty applies on sensors and cables). If it should become necessary to return the instrument for service during or beyond the warranty period, contact the Customer Service Department at (781) 890-7440 for authorization. A Return Authorization (RA) number must be issued before any product is returned to Extech. The sender is responsible for shipping charges, freight, insurance and proper packaging to prevent damage in transit. This warranty does not apply to defects resulting from action of the user such as misuse, improper wiring, operation outside of specification, improper maintenance or repair, or unauthorized modification. Extech specifically disclaims any implied warranties or merchantability or fitness for a specific purpose and will not be liable for any direct, indirect, incidental or consequential damages. Extech's total liability is limited to repair or replacement of the product. The warranty set forth above is inclusive and no other warranty, whether written or oral, is expressed or implied. Introduction Congratulations on your purchase of Extech’s 382356 Ground Resistance Tester. This Clamp-on device allows the user to measure the ground resistance of a ground rod without the use of auxiliary ground rods. This device can only be used on multi-grounded systems. It is not necessary to disconnect the ground under test. Proper use and care of this meter will yield years of reliable service. Safety Safety is the responsibility of the operator. Only qualified technicians should operate this meter. Use extreme caution when operating the meter near energized electrical equipment. Do not attempt to use this meter to twist or pry the ground electrode or ground wire away from grounded equipment. All metal objects or wires connected to the electrical system under test should be assumed to be lethal until tested. Grounded systems are no exception. Ensure that the batteries are inserted correctly in the battery compartment. Remove the batteries from the meter if the meter is to be stored for long periods. WARNING: If the meter is used in a manner not specified by the manufacturer, the built in protections provided by the meter may be impaired. 2 382356 V2.0 5/03 International Safety Symbols This symbol, adjacent to another symbol or terminal, indicates the user must refer to the manual for further information. This symbol, adjacent to a terminal, indicates that, under normal use, hazardous voltages may be present Meter Description 1. Jaw Assembly 2. Hold Button 3. Rotary Selector Switch 4. LCD Display 5. Measurement Trigger Display Symbols Ω Ohms. mA, A milliamps, Amps. •))) Continuity. NOISE Annunciator for excessive noise on the ground conductor or rod. Indicates that the clamp jaws are not fully closed. Low Battery. 3 382356 V2.0 5/03 Specifications General Specifications Resistance Test Frequency: 1.667KHz (15mV rms approx.) Max Conductor size 0.9” (23mm) Display 4-digit (9999 count) display Sampling rate 0.4 seconds Power supply One 9V battery Power consumption 40mA Temp. Coefficient 0.15 times the specified accuracy per degree o centigrade (from 39 to 64ºF (4 to 18 C) and 82 to o 122ºF (28 to 50 C)) Current Overload Protected to 100A Continuous; 200A for less than 60 seconds (50/60Hz) Continuity check Audible tone if reading is less than approx. 40Ω Range selection Automatic ranging Safety Meets the requirements for IEC1010-1 Category III 300V and Category II 600 V Operating conditions 4 to 122 F (-20 to 50 C) with < 85% RH Storage conditions -20 to 140 F (-28 to 60 C) with < 75% RH Dimensions 10.2 x 4.4 x 1.9” (258 x 110 x 47mm) Weight 24.7oz (700g) Accessories Resistance check plate, 9V battery, carrying case o o o o Ground Resistance (Autorange) Specifications Range Resolution Accuracy (of reading) 0.03 to 9.99Ω 0.02 Ω ± (1.5% + 0.1 Ω) 10.0 to 99.9 Ω 0.1 Ω ± (2.0% + 0.3 Ω) 100.0 to 199.9 Ω 0.4 Ω ± (3.0% + 1 Ω) typical 200.0 to 399.9 Ω 2Ω ± (5.0% + 5 Ω) typical 400.0 to 599.9 Ω 5Ω ± (10% + 10 Ω) typical 600.0 to 999.9 Ω 10 Ω Not specified 1000 to 1500 Ω 30 Ω Not specified Accuracy Note: Loop resistance non-inductive, external field < 50A/m, external electrical field <1 V/m, conductor centered 4 382356 V2.0 5/03 Ground / Leakage mA Current Specifications Range Accuracy (% of reading) 0.200 to 0.999mA ± (2.5% ± 0.05mA) 1.00 to 9.99mA ± (2.5% ± 0.05mA) 10.0 to 99.99mA ± (2.0% ± 0.3mA) 100.0 to 750.0mA ± (2.5% ± 3mA) (Autorange, 50/60Hz, True RMS, Crest Factor <3.0) Ground/Leakage A Current Specifications Range Accuracy (% of reading) 0.20 to 15A ±(2.0% ±0.05A) Max Current 100A Continuous; 200A for less than 60 seconds (50/60Hz, True RMS, Crest Factor <2.0) 5 382356 V2.0 5/03 Operating Instructions Note: The accuracy of measured readings will be affected if the clamp jaws are not fully closed. Pay special attention to ensure that the jaws are fully closed before testing begins. Note: DO NOT clamp on to any conductor or open the clamp jaws during the start-up self-calibration (display counts down from CAL 7 to CAL 0). Ground Resistance Measurements 1. Open the clamp jaws and check that all surfaces are clean and free of dust, dirt, or any foreign substances. Clean if necessary. 2. Snap the Jaws open and closed a few times so that they seat properly. 3. Turn the meter on by moving the rotary switch to the ohms Ω position. DO NOT interrupt the start up procedure by opening the clamp jaws or clamping around a conductor. 4. Once the start-up calibration procedure is completed, clamp on to an electrode or ground rod and read the value of ground resistance on the display. Typical application Continuity Loop Test The testing procedures are the same as for Ground Resistance measurements except that the rotary switch is set to the •))) position and an audible tone will sound if the measured resistance is below approximately 40Ω. RLOOP Ground / Leakage Current Measurement 1. Turn the meter on by moving the rotary switch to the mA or A position. 2. Clamp on to the electrode or conductor 3. Read the value of leakage current displayed on the display. 6 382356 V2.0 5/03 Principle of Operation Typical multi-grounded distribution system. Rn R2 Rg R1 Req If the parallel ground resistances, R1, R2, R3,etc, up to Rn are combined as Req, then only Rg and Req are left in the circuit I V Rg If a constant voltage is applied to the circuit, the following equation applies: V = R g + Req I Req = where: 1 , i = 1,2,...n 1 ∑ Ri If Rg and R1, R2, R3…Rn, are approximately the same, and n is large (200, for example), then Req will be much less then Rg and may possibly approach zero. Example: If Rg and R1, R2, R3…Rn are all 10Ω respectively and n = 200, then Req by calculation equals: Req = 1 = 0.05Ω 1 1 1 + + ... 10 10 10 7 382356 V2.0 5/03 V = R g + Req = 10 + 0.05 = 10.05 → R g I 8 382356 V2.0 5/03 Applications Telephone/Electrical Ground Rods 1. Remove any protective coverings from the ground conductor 2. Turn the meter to the Ohm Ω function. 3. Once the start-up calibration procedure is completed clamp on to an electrode or ground rod. 4. Allow several seconds for the meter to settle and note the reading. Cellular Transmission Towers WARNING: Use extreme care when making measurements around transmission towers. High Voltage may be present. The ground conductor should be located at the base of the tower, but your configuration may be different. 1. Locate the ground conductor 2. Clamp around the ground conductor. You should place the clamp before any splices, bonds or other splits in the ground system. 3. Read the measured reading. Primary Ground Conductor Transmission Tower Cement Pad Branch 9 Ground Conductors 382356 V2.0 5/03 10 382356 V2.0 5/03 Service Entrance Note: Multiple ground rods, multiple grounds i.e. ground rod(s) and water pipe grounds, or a combination may be present depending on the particular situation. In these situations it is necessary to make your measurements between the service-entrance neutral and all subsequent ground points. Distribution Panel Water Pipe Ground Rod 11 382356 V2.0 5/03 Trouble Shooting 1. Snap the jaws open and closed two or three times before turning the meter on 2. Do not clamp on to any device during the power-up initialization sequence. 3. Snap the jaws two or three times after clamping on to the ground electrode or rod. 4. Slight amounts of drift may occur at high resistance measurements. This is normal, and should not be cause for concern. Blank display or any failure mode Replace the battery before proceeding. Start-up Initialization Failure The start-up calibration will continue indefinitely if the jaws are open or dirty. Check that the jaws’ mating surfaces are clean. Do not open the jaws while the initialization sequence is running. Noise on the Ground Electrode or Rod If noise is present (over 3A or 30V) on the ground electrode or rod, the word “NOISE“ will appear on the display and readings can no longer be considered accurate. Before the meter can be used accurately, the noise problem must be addressed. Reference Test Loop The reference test loop is a set of resistors that provides a means to check the performance of the meter. 1. Open the measurement jaws and check that the mating surfaces are clean and free of dust, dirt, or any foreign substances. Clean if necessary. 2. Clamp the meter around the reference loop as shown in the diagram. 3. Give the meter a few seconds to settle and read the measurement. The meter should display approximately the same value as marked on the reference loop, taking into consideration the accuracy listed in the specification chart. If the readings are not similar to what is marked on the reference loop, consult the Trouble Shooting and Maintenance sections of this manual. 12 382356 V2.0 5/03 Maintenance General Care You should store your ground resistance tester and reference loop in its case when not in use. A damp cloth may be used to clean any surface dirt from the meter. Never use any harsh detergents or cleaners to clean your meter. Battery Replacement When the low battery symbol appears on the display, replace the meter’s 9V battery. Use a high quality alkaline battery whenever replacement becomes necessary. 1. Remove the two rear screws and open the meter housing. 2. Replace the battery, close the meter housing, and affix the two rear screws. Jaw Maintenance The jaws may be brushed clean with a toothbrush or similar soft-bristled brush. Care must be taken to ensure that the contact fins are not bent or deformed, as this will affect the operation of the meter. CALIBRATION AND REPAIR SERVICES Extech offers complete repair and calibration services for all of the products we sell. For periodic calibration, NIST certification or repair of any Extech product, call customer service for details on services available. Extech recommends that calibration be performed on an annual basis to insure calibration integrity. Tech Support Hotlines 781-890-7440 ext. 200 [email protected] www.extech.com Copyright © 2000 Extech Instruments Corporation. All rights reserved including the right of reproduction in whole or in part in any form. 13 382356 V2.0 5/03