Common problems of pipeline detectors

1. How does interference occur during detection?

The underground pipeline detector detects the electromagnetic field generated by the signal current on the target pipeline. Ideally, the electromagnetic field is in the form of standard concentric circles. There are two types of signals: passive and active. Passive signals are signals that exist on the pipeline itself (such as power cables), and active signals are signals that users apply to the target pipeline using a transmitter (the best method). The most common cause of interference is the coupling of signals on the target pipeline to adjacent pipelines. This is the "mutual inductance" phenomenon in physics. The interfering electromagnetic field causes the receiver to "see" a deformed electromagnetic field, resulting in inaccurate readings. For a given electromagnetic field, the higher the frequency, the greater the interference.

2. Why do I detect interference signals on other pipelines?

The signal is coupled into other lines through a common ground point or mutual inductance. Make sure you use the direct connection method to apply the signal and use a lower frequency.

3. How to use the valley method to verify the accuracy of the peak method positioning?

For an ideal interference-free pipeline, the peak/zero positioning positions are overlapped. However, for accompanying pipelines or other interferences, the peak/zero positions will not overlap. At this time, you must pay attention to the distance of the peak/zero positioning point and use it to correct the positioning point. At this time, the true position of the pipeline is on the side of the peak, half the distance of the peak/zero position from the peak point. When the interference is serious, the zero point may not be found. At this time, the position of the pipeline can only be roughly given based on the peak position. It is best to change the method of applying the signal and re-position the pipeline. In addition, positioning should not be performed at the turning point, tee, or depth change point of the pipeline, but the extension line method should be used for positioning. When the peak/zero position does not overlap, the direct reading depth measurement of the pipeline will also have a large deviation, and even the depth cannot be read.

4. What methods can be used to reduce the deformation of the electromagnetic field shape of pipelines?

First, you can try to reduce the output power of the transmitter. Sometimes the signal is too strong and the detection effect may not be the best, especially when multiple pipelines are very close. If you use the induction method to apply the signal, you can try to see if you can use the direct connection method or clamp method to apply the signal. This can reduce the signal coupled to other pipelines, thereby reducing the deformation of the electromagnetic field of the pipeline. If you find that the positioning of the valley method and the peak method are inconsistent, change to a consistent place for positioning. If you can't find a consistent place, we usually use the peak position as the position of the pipeline, and the depth measurement is also carried out in the peak mode. Of course, there is a certain error, but it is closer to the true value than the valley method.

5. Can the device be used to detect both copper and fiber optic cables?

Current underground pipeline detectors can only detect cables with metal sheaths or cores (ground penetrating radar has been used to detect non-metallic cables in recent years). Only optical cables with metal sheaths or central metal reinforcement cores can be detected with underground pipelines. To detect cables, a detectable signal (transmitter signal) must be applied to the conductor.

6. Why is my receiver's depth measurement inaccurate?

If the problem still exists, check whether the peak value method and the valley value method are consistent. If not, try other frequencies or connection methods. Although the direct reading depth measurement method is simple, it requires certain conditions to read the correct result, otherwise the measurement accuracy is not high, or even an incorrect result is obtained. One of the conditions for applying direct reading depth measurement is that the peak and zero values ​​at this time should basically coincide, generally less than 20 cm, otherwise the error will be large. The second is that the direct reading depth must be calibrated to achieve higher reliability. The correction factors include: the moisture of the soil where the pipeline is buried, and the frequency of the detection signal. Generally, the greater the soil moisture and the higher the detection frequency, the smaller the correction coefficient should be, generally between 0.8-0.95. The simple way is to find a pipe section with a known depth and no interference, measure the direct reading depth, and compare it with the actual burial depth to obtain the correction coefficient; when measuring the burial depth, pay attention to the direction of the receiver, and try to make the receiver's coil perpendicular to the direction of the pipeline. This requirement can be achieved by slightly rotating the receiver to make the display reading on the panel reach the maximum value. In addition, it should be noted that the direct reading burial depth value is the distance from the ground of the receiver body to the center of the pipeline.

7. What is the maximum distance that a fiber optic cable can be traced using a signal?

If the metal sheath is continuous and not short-circuited to the ground, the signal transmission distance is usually 80 kilometers. In addition, the performance of the receiver is also an important factor affecting the detection distance (the key is the receiver's ability to suppress noise).

8. What is the reason for the sudden decrease in signal strength?

If you encounter a sudden decrease in signal strength, the pipeline may have changed direction. At this time, you should stop moving forward and check the current measurement value. The current value measured at the beginning of the positioning should remain unchanged throughout the detection process. Carefully search the nearby area, find the center line, and measure the current to check whether you are above the target pipeline.

If the current measurement suddenly decreases, it may have passed through a T-type split or branch pipe. Scan 360 degrees in the area, looking for other center lines to confirm whether the conductor has branched.

If the current measurement suddenly decreases, it may have passed through a T-type split or branch pipe. Scan 360 degrees in the area, looking for other center lines to confirm whether the conductor has branched.