The Difference between Live Cable Recognition Instrument and

1. Operators should read the instructions beforehand and master the functions, working methods, preparation before testing and correct testing requirements of the instrument.

 

2. Before the test, the armoured grounding at both ends of the cable under test is disconnected, and the distal end of the core wire is connected to the earth.

 

3. The two output lines of the instrument are respectively clamped red to the core line of the cable under test and black to the earth as required.

 

4. Before turning on the transmitter, it is necessary to turn the output adjustment knob back to zero, and then turn on the transmitter. Slowly adjust the output adjusting knob, so that the output reaches 5A-15A (adjusting knobs are generally within two-thirds of the range). If the grounding resistance of the distribution system is greater than 4 ohms, the output current is less than 8A, so long as the receiver head can deflect in both directions, it can work normally. 1. Note: If the grounding resistance is too small, the output current of the transmitter will be very large when the counter-clock of the output adjusting knob is turned to zero, and the protective circuit in the transmitter will act (as the head of the watch has a small swing). At this time, the randomly matched high-power test resistors (1 to 2 ohms/20W-30W) can be connected in the transmitter circuit.

 

2. In the actual test, there are more than two other cables connected between two distribution rooms in the same cable trench. The grounding resistance becomes very small or even close to zero because of the armor connection of other running cables. The output current of the transmitter is too large and the protective circuit operates. At this time, the test resistance can be connected in series to the transmitter circuit for testing. After testing, the temperature of the test resistance is very high. Pay attention to packing after cooling. The test resistance can also be replaced by other resistors of 1-2 Euros, greater than 20W.

 

Fifth, before identifying the cable in the field, the receiver of the identifying instrument should be calibrated at the beginning of the cable according to the requirements of instrument calibration in the instruction.

 

6. Standard for identifying cables on site: When the sensor card is tested on one cable, the receiver head deflects to one side and swings greatly. When testing on the other cables (keeping the same direction of the sensor in the same direction), the receiver head deflects to the other side and swings less, and the more the cables, the smaller the deflection. The cable that the receiver head deflects to one side and swings greatly is the cable that needs to be identified.