Operating Specifications for Clamp-on Ground Resistance Tester

I. Before Measurement: Preliminary Confirmation and Safety Check
(1) Applicability Confirmation (Core Premise)
This instrument is only applicable to grounding systems that have formed a loop, such as continuous grounding of multiple towers or grounding grids of buildings. This is a basic requirement of relevant regulations such as DL/T 475-2017 “Guidelines for Measuring Characteristics of Grounding Devices”. This measurement method is not applicable to independent grounding electrodes.
(2) Environmental and Equipment Inspection
Safety Confirmation: Check the testing environment to ensure there are no flammable or explosive gases. If operation is required on energized equipment, strictly follow the “Electric Power Safety Work Procedures” and wear appropriate insulating protective equipment.
Equipment Inspection: First, check if the instrument appearance is intact, the jaws are clean, and the closing state is good. After powering on, use the standard test ring provided with the instrument for calibration to confirm that the instrument reading is consistent with the nominal value of the test ring. This is the first step to ensure measurement accuracy.
II. During Measurement: Standard Operating Procedures and Interference Handling
(1) Standard Operating Procedures
Fully open the jaws, tightly close on a single grounding lead wire, and avoid clamping multiple wires or flat iron at the same time. Wait for the instrument reading to stabilize before promptly recording relevant data.
(2) Interference Handling
If the reading fluctuates in a strong electromagnetic field environment such as a substation, refer to the recommended measures in the regulations:
Change the jaw direction to weaken magnetic field interference;
Under conditions permitted and ensuring safety, perform the measurement after a short power outage to obtain the most accurate measurement data.
III. After Measurement: Data Processing and Instrument Maintenance
(1) Data Recording
Completely record the measured values, measurement locations, and environmental conditions, etc., as key information.
(2) Result Judgment
Compare the measured values with design values, historical data, and regulatory standards (such as those in GB/T 50065-2011 for various grounding resistances) to determine whether the measurement results are qualified.
(3) Equipment Maintenance
After the measurement, clean the jaws promptly and store the instrument properly in a dry environment.
IV. Important Precautions and Standard References
(1) Standards and Regulations
Mainly follow DL/T 475-2017 “Guidelines for Measuring Characteristics of Grounding Devices”. This regulation clearly stipulates the applicable conditions, measurement methods, and interference handling methods of the clamp method. At the same time, specific industry-related regulations should also be taken into account, such as YD/T 1429 in the communication industry.
(2) Understanding of Reading Limitations
 When the grounding system is operating well and there are multiple parallel paths, the measured reading may be much lower than the actual resistance of a single grounding electrode. This is a normal phenomenon, but it does not prove that a single grounding electrode meets the qualified standards. If there is suspicion that a single grounding electrode is deteriorated, the segmented measurement method using the pile driving method should still be employed.
(III) Safety Red Lines
It is strictly prohibited to conduct outdoor grounding measurement work during thunderstorm weather;
It is strictly prohibited to work on high-voltage equipment without confirming safety;
It is strictly prohibited to use the instrument beyond the measurement range or to measure wires with voltages exceeding the specified range of the instrument.