**Testing Method for Lightning Protection Grounding Tester in Henan School Lightning Protection Project**
**Grounding Resistance Test Requirements:**
a. AC working grounding resistance should not exceed 4Ω.
b. Safe working grounding resistance should also be less than or equal to 4Ω.
c. DC working grounding resistance depends on the specific requirements of the computer system.
d. The grounding resistance for lightning protection systems must not exceed 10Ω.
e. For shielded systems with combined grounding, the resistance should not be higher than 1Ω.
**Grounding Resistance Tester (ZC-8 Type):**
The ZC-8 grounding resistance tester is a versatile device used for measuring the resistance of various power systems, electrical equipment, lightning rods, and other grounding installations. It can also measure low-resistance conductors and soil resistivity. The instrument features a hand-cranked generator, current transformer, sliding wire resistor, and galvanometer. All components are housed in a durable plastic case, making it easy to carry. The accessory kit includes auxiliary probe wires, which are stored in a dedicated bag.
**Working Principle:**
The ZC-8 operates using a reference voltage comparison method. This ensures accurate measurement by comparing the measured value against a known standard.
**Preparation Before Use:**
Before starting the test, ensure all components are present:
1. One ZC-8 grounding resistance tester
2. Two auxiliary grounding rods
3. Three wires of 5m, 20m, and 40m length each
**Usage and Operation:**
(1) When measuring grounding resistance, connect the E terminal of the instrument to the 5m wire, the P terminal to the 20m wire, and the C terminal to the 40m wire. The other ends of the wires should be connected to the grounding electrode (E’), potential probe (P’), and current probe (C’). These probes should be placed in a straight line, spaced 20 meters apart.
(2) For measurements below 1Ω, connect both E-terminal wires directly to the grounding body being tested to eliminate errors caused by the resistance of the connecting wires.
**Operation Steps:**
1. Ensure all wiring connections on the instrument side are correct.
2. Securely connect the instrument’s wires to the grounding electrode (E’), potential probe (P’), and current probe (C’).
3. Place the meter on a flat surface and adjust the galvanometer to zero.
4. Set the "magnification switch" to the highest level and gradually increase the crank speed to 150 revolutions per minute. If the galvanometer pointer deflects, adjust the dial until the pointer returns to "0." The measured resistance value is the dial reading multiplied by the magnification factor.
5. If the dial reading is less than 1 and the pointer remains unbalanced, switch to a lower magnification setting until balance is achieved.
6. If the galvanometer pointer shows instability, adjust the crank speed to stabilize the reading.
**Precautions:**
1. Never perform measurements during thunderstorms or when the object under test is energized.
2. Handle the instrument carefully to avoid shocks or vibrations that could affect accuracy.
**Conclusion:**
Proper use of the ZC-8 grounding resistance tester is essential for ensuring the safety and effectiveness of the lightning protection system at Henan School. Following the outlined procedures and precautions will help achieve reliable and accurate grounding resistance measurements.
**Source:** China Hardware Business Network http://news.chinawj.com.cn
**Image:** [Test method of lightning protection grounding resistance tester for lightning protection project of Henan school](http://i.bosscdn.com/blog/91/01/30/25678.jpg)
**Editor:** Hardware Business Network Information Center http://news.chinawj.com.cn
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