I. Host preparation
1. Connection:
(1) Before testing, the cable under test should be cut off and its surrounding environment should be in a safe state.
(2) The generator is connected with the cable under test, and the red clamp is connected with one or several core wires of the identified cable. Connect the black clip to the nail.
(3) Connect the core wire of the distal end of the cable with the ground nail.
(4) disconnect the armor at both ends of the cable from the ground wire.
(5) Insert the power cord into the power socket.
2. Turn on:
(1) Turn on the power switch of the main engine to supply power to the main engine.
(2) The main engine starts to send pulsating DC signal to the cable intermittently, and the output pulsating current signal is about 30A.
3. Receiver preparation
(1) Slowly adjust the sensitivity knob so that the meter can start to indicate.
(2) Pay attention to the direction of the sensor insertion cable and the swing amplitude of the receiver head.
II. Testing
1. Setting up test circuit
In order to ensure the normal use of the instrument, attention should be paid to setting up the test circuit.
Connect the red output jack to the core of the cable to be identified, the black output jack to the ground, and the cable core to the ground at the far end.
The output current flows to the far end along the arrow direction in the cable. By returning to the generator through the earth, all the core wires of the identified cable can be connected together, and a clear signal can be obtained.
2. Instrument calibration
When calibrating the receiver, the sensor should be used at the beginning to clamp the cable (close to the generator). The arrow points to the current direction, that is, to the far end of the cable. Then, the same sensitivity is used to test at the need to detect. Each cable is clamped once with the sensor, and the arrow direction points to the far end of the cable. When the cable needs to be identified is clamped, the readout of the receiver's watch head is 4-6. Lattice, and to the right. All other cables either have no readings or have very small readings and the current is in the opposite direction, i.e. to the left.
3. Examples of testing
Example 1:
Because the cable shielding layer is usually connected to the ground, if other cables are also connected to the public ground in the cable bundle, the black output jack on the generator can be connected to the public ground. The return current is distributed in several cable shielding layers, and the return current is divided into many branches, which means that the differential current of the identified cable is larger and the useful signal is clearer. The "difference" means the output current. The return current is in the same channel as the return current. As shown in Figure 4, there are 5 cables in Figure 4. Cable No. 4 is what we need to identify. The "output current" of the cables to be identified is 20A. Assuming that the return current is evenly distributed among the shielding layers of all cables, there should be a return current of 4A in the cables to be measured. The difference in the cables to be identified is 20A (output) - 4A (return) = 16A (difference)
Example 2:
If the shielding layer of the cable under test is disconnected from the system, the difference will be improved. There is no return current in the shielding layer of the cable. As shown in Figure 5
There are 5 cables in Fig. 5. Cable No. 4 is the cable we need. The "output current" of the cable to be identified is 20A. Due to the disconnection of shielding layer and ground, the return current of the remaining four cables is 20A/45A, and the current difference of the cables should be identified as 20A-0=20A.
Example 3:
The smaller the number of shielding layers used as the return circuit, the smaller the reading obtained from the difference method, and the limit case is that there are only two cables. As shown in Figure 6
There are two cables in Fig. 6. Cable No. 1 is the cable to be identified. The output current of the cable to be identified is 20A, and the return current is distributed in the shielding layer of the two cables. Therefore, the return current of the shielding layer of each cable is 10A, and the current difference is 20A-10A=10A. The differential current will be improved by disconnecting the cable shield layer from the public ground, improving the grounding condition of the generator and adding a pin to the distal end of the cable. As shown in Figure 7
There are two cables in Figure 7. Cable No. 1 is the cable to be identified. The output current of the cable to be identified is 20A, and the return current is 10A in the shielding layer of cable No. 2. The value current generated is 20A-0A=20A.
Example 4:
If there is no shielding layer to constitute the return circuit, the return circuit can be realized by the ground pin. At this time, two ground pins are needed, one is connected to the cable core at the far end of the current, the other is connected to the black output jack of the host, as shown in Figure 8.
There are two cables in Figure 8. Cable No. 1 is the cable we want to identify. The output current of the cable is 20A. The return current is returned to the generator through the ground pin. To ensure that the impedance of the loop resistance is as low as possible, the ground nail should be in good contact with the ground nail (wetting the place near the ground nail).
Main Functional Characteristics of Cable Recognition Instrument
1. Recognition is correct;
2. Large identification clamp is suitable for all kinds of cables.
3. The operation is very simple.
4. Clear and intuitive instructions;
5. The main and auxiliary parts are portable, beautiful and feel good.
6. The whole machine works reliably without fear of short circuit.
7. The output frequency of the power supply and the sensitivity of the receiver are adjustable and suitable for various fields.
