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CLAMP ON EARTH RESISTANCE TESTER

MEASURING METHOD of MET-1/MET-2 Clamp Earth Tester

In the equivalent circuit, approx.160mV p-p (MET-1) or approx.. 320mV p-p (MET-2) is injected from Injection CT by changing frequency from 4 KHz to 400 KHz (MET-1) or 4KHz to 200KHz (MET-2).
Then, the resonance will happen by L & C0 or r & C1 in the circuit and the resonance current will flow. At the time of resonance, the current will be maximum.
By detecting this resonance current, the current value at resonance point (IZ) and synchronous current at injected frequency can be
calculated and the earth resistance can be displayed.

At the time of resonance by L & C0, current I will flow as the above route and can measure Re (Earth Resistance).
*Cannot measure the resistance in no-looping circuit like as grounding line connected with lightening rod but can get the value by
connecting with other grounding lines, using the subsidiary lead wire.

Application Example
1. Measurements for the active line

The earth resistance can be measured by clamping 2 CTs near at transformer (point A or B) and near at the electrical loading part (motor, electric appliance, etc.)

2. Electric installation

“ sigma” shows the clamping point of the injection CT and the measuring CT.

3. Earth resistance measurements for telecommunication
system

4. Measurements where L (inductance) & C (capacitance) are
low

Where L & C resonance has not been gotten, this instrument may show “OVER” at the display. In this case, connect the objective grounding line (EA) to other grounding lines (EB or ED) by the subsidiary lead wire and clamp 2 CTs at the measuring point (EA). Even in the case of no resonance between L & C, the multiple earth resistance can be measured.

MET-1

FEATURES

  • Completely different method from the ordinary Earth Testers.
  • Just clamping two CTs to the earthing conductor and no need to use auxiliary earth rod.

MET-2

FEATURES

  • Completely different method from the ordinary Earth Testers.
  • Just clamping two CTs to the earthing conductor and no need to use auxiliary earth rod.
specifications MET-1 MET-2
Measuring function Earth Resistance, AC Current (Load and Leakage)
Accuracy(Earth resistance) (23℃ ± 5℃, 85% RH or less)
Range / Resolution / Accuracy
200Ω / 0.1Ω / 0 ~ 10Ω : ±0.2Ω,
200Ω / 0.1Ω / 10 ~ 50Ω : ±1.0Ω,
200Ω / 0.1Ω / 50 ~200Ω : ±5.0Ω
(23℃ ± 5℃, 85% RH or less)
Range / Resolution / Accuracy
10Ω / 0.01Ω / 0.1~1Ω :±0.1Ω,
10Ω / 0.01Ω / 1~10Ω :±0.5Ω
300Ω / 0.1Ω / 10~50Ω :±2.0Ω,
300Ω / 0.1Ω / 50~150Ω: ±5.0Ω
300Ω / 0.1Ω / 150~200Ω :±20Ω,
300Ω / 0.1Ω / 200~300Ω :±30Ω
Accuracy(AC current) (23℃ ± 5℃, 85% or less)
Range / Resolution / Accuracy
200mA / 0.1mA / 2% rdg ± 8dgt
2000mA / 1mA / 2% rdg ± 8dgt
20A / 0.01A / 2% rdg ± 8dgt
(23℃ ± 5℃, 85% RH or less)
Range / Resolution / Accuracy
200mA / 0.1mA / 3% rdg ± 8dgt
2000mA / 1mA / 2% rdg ± 8dgt
20A / 0.01A / 2% rdg ± 8dgt
Injection signal Approx. 320mVp-p, Auto sweep 4KHz~400KHz Approx. 160mVp-p, Auto sweep 4KHz~200kHz
Measuring time Approx. 30 second for earth resistance
Measuring CT φ34mm with 2.5m lead
Injection CT φ34mm with 2.5m lead
Safety standard IEC 61010-1, IEC61010-2-032
Installation CAT II 600V or CATⅢ 300V
Display LCD, 16 letters/characters × 2 lines
with contrast adjuster
A/D Conversion Dual slope integration mode
Sampling Approx. 2 times/sec. for AC current
Memory function - 200 measuring data can be stored and displayed
Auto power off function Approx. 5 minutes after power on
Over range indication "OVER" on LCD
Data hold indication "DH" mark on LCD
Low battery indication "B" mark on LCD
Limitation of circuit voltage Less than 600V Less than 500V
Withstanding Voltage AC 3700V, 1 minute( between CT core and CT handle)
Insulation Resistance More than 100MΩ (between CT core and CT handle)
Operating Temperature 0℃~40℃, < 85%RH ( without condensation)
Storage Temperature -10℃~60℃, < 80% (without condensation)
Size and Weight Measuring CT:90.5(W)×165(H)×38(D)mm, approx.460g
Injection CT:90.5(W)×165(H)×38(D)mm, approx.440g
Main unit:190(W)×140(H)×42 (D)mm, approx.800g
Battery life 450 times measurements under full charged condition
(Subject to the times of charging and discharging)
Approx.400 times measurements under full charged condition
(Subject to the times of charging and discharging)
Battery charger AC200V~240V (50/60Hz)
Power supply NiMH battery pack (1.2V x 5)
Accessories : Measuring CT: 1
Injection CT: 1
Battery charger: 1
Carrying case: 1
Subsidiary lead wire:1 (Optional in MET-1)
Instruction manual:1