The pipeline detector basically has the following three detection methods: direct connection method, clamp method and induction method. However, the use frequency of pipeline detector can be basically divided into two categories: high frequency and low frequency. Low frequency attenuation is slow, transmission distance is long, radiation is small, it is not easy to connect in series, but penetration is poor; High frequency band high frequency band, strong penetration, large radiation, but fast attenuation and close distance. Therefore, the appropriate working frequency should be selected according to different methods. 1ã Direct connection method direct connection method is to load the signal sent by the transmitter directly onto the pipeline to be detected by the pipeline detector. Direct connection method is the best signal processing method, which is usually preferred when conditions permit. Direct connection mode is adopted, the signal is stable and not easy to be disturbed by other pipelines. In practice, cast iron pipelines and steel pipes are recommended to be tested by direct connection method, in which the use frequency can be selected according to the material of the pipeline, and the steel pipe can use low frequency, because the steel pipe has good conductivity, and the use of low frequency can be transmitted further. However, it should be noted that the signal of direct connection mode will be transmitted in two directions along the pipeline and distributed unevenly. The grounding point should be a certain distance (& gt; 5m) from the pipeline. The ground wire needle should be inserted in the soil and watered if necessary to reduce the ground wire resistance, which is conducive to signal transmission. 2ã Clamp method can be used when the signal cannot be directly loaded on the pipeline. The method is to connect the signal of the transmitter with the target pipeline through a clamp. The invention is applicable to communication, power and other pipelines. Generally, when this method is adopted, the use frequency can be selected according to the external interference. In the case of small external interference and extremely poor conductivity of the pipeline, high frequency can be used as induction. Generally speaking, we can detect with a frequency of about 33 kHz. Pay attention when using the pliers. The jaws of the pliers should be closed. In addition, although it is convenient to apply signals, the transmission distance and signal stability of this method are worse than those of the direct connection method. 3ã As the name suggests, induction method is to directly sense the signal of the transmitter to the target pipeline through non-contact mode. Generally speaking, this method can be used only when direct connection and clamp cannot be used. However, this method is greatly affected by the surrounding environment, and will produce a lot of interference when the vehicle passes through or the pipeline is close to the metal. Therefore, when selecting the frequency again, we must pay attention to avoid using high frequency for detection as far as possible, because the high frequency excitation range is large, which will cause serious interference between pipeline signals. In use, it should be noted that the distance between the transmitting end and the receiving end should be kept 10m as far as possible to avoid the frequency of the transmitting end interfering with the signal. In terms of methods, such a rule is generally followed. Direct connection can be used without pliers, and induction can be used without pliers. Frequency selection is also to select low-frequency detection as much as possible according to specific conditions. This ensures that more accurate conclusions can be drawn when using the pipeline detector.