USER MANUAL Ground Resistance Clamp‐On Tester MODEL 382357
Introduction Congratulations on your purchase of Extech’s 382357 Ground Resistance Tester. This Clamp‐on device allows the user to measure ground resistance 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. This meter is shipped fully tested and calibrated and, with proper use, will provide years of reliable service. Please visit our website (www.extech.
Description 1. Jaw Assembly 2. Hold Button 3. Rotary Selector Switch 4. LCD Display 5. Record Button 6. ▼(decrement) Button 7. ▲(increment) Button 8. Function Button 9. Measurement Trigger 1 2 3 9 4 5 8 Display Symbols 1. REC: Indicates data logging in progress 2. NO. Indicates the READ function 3. : Clamp jaws are not fully closed 4. NOISE: Excessive noise on the ground conductor or rod 5. ))): Hi Lo alarm position 6. Function or Record display 7.
Operation Note: Ensure that the jaws are fully closed before testing. Note: DO NOT clamp on to any conductor or open the clamp jaws during the start‐up self‐ calibration (self‐cal is identified by the LCD counting down from CAL7 to CAL1). 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. Forcefully snap the clamp jaws open and closed several times. 3.
High and Low Alarm 1. Turn the meter on by moving the rotary switch to the ))) position. 2. Press the FUNC button to view and adjust the “HI” alarm value. 3. Press ▲ or the ▼ button to increase or decrease the value. Hold down the button to increase the speed of adjustment. The value can be incremented from 0 to 1500 ohms and then OL (overload). The value will roll over to 0 after OL is displayed. 4.
Recalling Stored Data 1. Press the FUNC button four times until the “NO.” symbol is displayed on the LCD. The current record number will be displayed in the top row and the data will be displayed below it. 2. Press the ▲ or the ▼ button to step through and read the data in the next memory location. Holding down the button will increase the speed of the incrementing value. Clearing Data Memory 1. With the meter powered off, press and hold down the REC button while turning the meter on.
Measurement Principles Typical multi‐grounded distribution system 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.
Applications Telephone‐Electrical Ground Rods 1. Remove any protective covering from the ground conductor 2. Turn the meter switch to the Ohm 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 then note the reading. Cellular Transmission Towers WARNING: Use extreme care when making measurements around transmission towers; High Voltage may be present.
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 Troubleshooting 1. Snap the jaws open and closed two or three times before turning the meter on 2.
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.
Maintenance General Care Store the 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 harsh detergents, abrasives, solvents, or cleaners on the 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.
Specifications General Specifications Resistance Test Frequency: 3.333 kHz (15mV rms approx.) Max Conductor size 23mm (0.9”) Display 4‐digit (9999 count) display Sampling rate 0.5 seconds Memory 116 records Datalogging sample rate 1 to 255 seconds Power supply One (1) 9V battery Power consumption 40mADC Battery Life 3000 measurements Temp. Coefficient o o 0.
Ground Resistance (Autorange) Specifications Range Resolution Accuracy (of reading) 0.025 to 0.250 0.002 ± (1.5% + 0.05 0.250 to 1.000 0.02 ± (1.5% + 0.05 1.001 to 9.999 0.02 ± (1.5% + 0.1 10.00 to 50.00 0.04 ± (2.0% + 0.3 50.01 to 99.99 0.04 ± (2.0% + 0.5 100.0 to 200.0 0.4 ± (3.0% + 1.0 200.1 to 400.0 2 ± (5.0% + 5 400.0 to 600.0 5 ± (10% + 10 600.
