EARTH MEASUREMENT WITH 3P METHOD
The 3P method is the traditional method using rods to measure the resistance of an existing earth connection. The C.A 6470N & C.A 6471 can also be used to measure the resistances of the auxiliary rods RS and RH, as well as any disturbance voltages. Suitable for all types of measurement environments, even the most difficult, this method guarantees measurement of auxiliary-rod resistances up to 100 k½ and disturbance voltages of 60 Vpeak.
EARTH MEASUREMENTS 4P AND SELECTIVE 4P EARTH MEASUREMENT
The 4P measurement method is particularly suitable for measuring very low earth resistances. If there are several resistances connected in parallel, it is possible to use the instrument with a clamp-on ammeter to carry out selective measurements, in order to avoid the effect of the parallel earth connections. This "selective 4P" measurement method saves considerable time because it is no longer necessary to disconnect the earth resistance before measuring it. In the event of a system with parallel earth connections, 2 clamp-on ammeters can be used with the C.A 6470N & C.A 6471 to provide accurate earth resistance measurements. The principle of this method involves placing 2 clamps around the earth conductor tested and connecting each of them to the instrument. One clamp injects a known signal (32 V / 1367 Hz) while the other clamp measures the current flowing in the loop. This method saves considerable time when earth testing because it is no longer necessary to set up auxiliary rods or disconnect the earth connections, which is often timeconsuming
MEASUREMENT OF EARTH COUPLING
To estimate the reciprocal influence of 2 normally unrelated earth resistances, you must calculate the coupling coefficient, which should be as low as possible. The operator takes 3 successive measurements (2 classic earth measurements using the classic 3P - R1 & R2 method, and 1 earth measurement using the 2P – R1-2 method. The instrument then automatically calculates the coupling resistance: Rc = (R1 +R2 –R1-2) / 2.
SOIL RESISTIVITY MEASUREMENT When it is possible to choose the position of the earth connection, resistivity measurements can be used to check the soil and determine where the earth resistance will be lowest (optimization of building costs). The C.A 6472 automatically calculates soil resistivity using the Wenner or Schlumberger methods as soon as the distances between the rods have been entered. The resistances of the rods RE, RES, RS and RH can also be measured.
Multi-function earth tester
Model | 6471 |
Electrical | |
2 Clamp Measurement | |
Range | O.01 to 500Ω |
Resolution | 0.01 to 1Ω |
Measurement Frequency | Auto: 1367Hz Manual: 128Hz-1367Hz-1611Hz-1758Hz |
3-Point Measurement | |
Range (Auto-Ranging) | 0.09Ω to 99.9kΩ |
Resolution | 0.01Ω to 100Ω |
Test Voltage | Nominal 16 or 32VRMS user selectable |
Resistance Measurement Frequency | 41 to 513Hz automatic or user selectable |
Test Current | Up to 250mA |
Accuracy | ±2% of Reading + 1ct @ 128Hz |
Soil Resistivity 4-Point Measurement | |
Test Method | Wenner or Schlumberger selectable with automatic calculation in Ω-meters, Ω-cm or Ω-feet |
Range (Auto-Ranging) | 0.01 to 99.99kΩ; ? Max: 999kΩm |
Resolution | 0.01 to 100Ω |
Test Voltage | 16 or 32V user selectable |
Frequency | From 41 to 128Hz selectable |
External Voltage Measurement | |
Range (Auto-Ranging) | 0.1 to 65.0Vac/dc – DC to 440Hz |
Accuracy | ±2% of Reading + 1cts |
Resistance Measurement (Bond Testing) | |
Measurement Type | 2-Pole (with lead resistance compensation) or 4-Pole (Kelvin sensing) user selectable |
Range (Auto-Ranging) | 2-Pole 0.01O to 99.9kΩ; 4-Pole 0.001O to 99.99kΩ |
Accuracy | ±2% of Reading + 2cts |
Test Voltage | 16Vdc (+, - or auto polarity) |
Test Current | Up to 250mA max |
Data Storage | |
Memory Capacity | 512 test results |
Communication | Optically Isolated USB |
Power Source | 9.6V rechargeable battery pack |
Recharging Source | 110/220 50/60Hz external charger with 18Vdc, 1.9A output or 12V vehicle power |
6470C 4-Point Ground Resistance Testers The Ground Resistance Tester Model 6470C is a portable measurement instrument designed to measure Ground Resistance with 2 clamps (no auxiliary rods), Bond/Connection Resistance (2-Pole and 4-Pole Kelvin sensing), Ground Resistance (3-Pole or 4-Pole), Ground Coupling Resistance, and Selective Ground Resistance, Soil Resistivity (Wenner or Schlumberger method). The Model 6470C measures from 0.01 to 99.99kO and is auto-ranging, automatically seeking out the optimum measurement range, test frequency and test current. Easy-to-use - Simply connect the leads, select the test mode, press Start and read the results. Up to 512 test results can be stored in internal memory for later recall to the display or downloaded to a PC via DataView® software. The Model 6470C is Cat IV rated to 50V and is over voltage protected to more than 250VAC against accidental connection to live circuits. The voltage is also displayed on screen. In the event of a system fault, the Model 6470C can withstand 250VAC. Additional features of the Model 6470C include a heavy-duty field case sealed against dust and water when closed (the test button is also sealed against the elements); manual and automatic test frequency selection from 41 to 513Hz; user selectable 3-Pole Fall of Potential or 4-Pole Soil Resistivity test methods and user selectable 2-Pole or 4-Pole Bond Resistance test method. The Ground Resistance Tester Model 6470C is rugged, easy-to-use and ideal for maintenance crews performing numerous tests. It exceeds mechanical and safety specifications for shock, vibration and drop tests per IEC standards. The adjustable test frequency provides for rejection of high levels of interference, allowing it to be used under difficult conditions such as high stray currents that affect accuracy.
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