According to the detection principle, the underground pipeline detector is divided into two categories. One is the use of electromagnetic induction principle to detect metal pipelines, electric cables, and some non-metallic pipelines with metal marking lines, such as pipeline detector, ultrasonic thickness gauge and electromagnetic wave to detect underground pipelines of all materials. It can be used to find buried objects underground, commonly known as radar, also known as pipeline radar.
Generally speaking, the underground pipeline metal detector is composed of two parts: transmitter and receiver. Transmitter: To apply a special frequency signal current to the pipeline under test, three excitation modes are generally adopted: direct connection method, induction method and clamp method. Receiver: The receiver has built-in induction coil, which receives the magnetic field signal of the pipeline. The coil generates the induction current, thus calculating the direction and path of the pipeline.
Generally speaking, the transmitter of underground pipeline detector has three receiving modes: peak mode (maximum), Valley mode (minimum) and wide peak mode; moreover, more advanced instruments now generally have peak arrow mode (combining the advantages of peak and valley, making operation more intuitive) and compass guidance (used to indicate the direction of pipeline).
The underground Metal pipeline detector is based on the principle of electromagnetic induction to detect the precise direction and depth of underground metal pipelines and cables, as well as the fault points of pipeline sheath. The intelligent Chinese character, graphic operation instructions and voice frequency modulation instructions of underground pipeline detectors make it the most easily used underground pipeline detector. The transmitter built-in ohmmeter can automatically measure the loop resistance and the continuous automatic output impedance matching. The ultrasonic thickness gauge ensures the best matching signal output. According to the need of practical application, the coupling clamp can be selected to find the path of live cable without power failure. The 50Hz detection function of the receiver can also be used to track the 50Hz power frequency signals from the running cables, which truly achieves a multi-purpose machine and has the best performance-price ratio.
The basic working principle is that the electromagnetic wave generated by the transmitter is transmitted to the underground metal pipeline detected by different transmission connections. After the underground metal pipeline is induced to the electromagnetic wave, the induced current is generated on the surface of the underground metal pipeline, and the induced current will propagate along the metal pipeline to the far distance, and the underground metal will also pass through the underground metal during the propagation of the current. The pipeline radiates electromagnetic wave to the ground, so when the receiver of underground pipeline detector detects on the ground, it will receive the electromagnetic wave signal on the ground directly above the underground metal pipeline. The position and direction of underground metal pipeline can be distinguished by the change of the received signal strength.