Metal Detector - Pulse Inductive (PI)
Useful for searching at depth and in difficult conditions
Pulse Inductive (PI) metal detectors are a type of detector that are particularly useful for searching at depth and in challenging conditions such as salt water or highly mineralized soils. This type of detector works on a different principle than traditional VLF (Very Low Frequency) detectors.
The principle of operation of PI detectors:
-
Pulse generation:
- PI detectors generate a series of short and strong magnetic pulses that are transmitted to the ground through a coil. These pulses are able to penetrate deep into the ground.
-
Thetime between pulses:
- There is a short time interval between each pulse during which the detector is switched to receive mode. During this period, the detector "listens" and records any electromagnetic signal that is returned.
-
Response from metallic objects:
- When a magnetic pulse strikes a metallic object, it induces currents in the object called eddy currents. These currents then generate their own magnetic field, which is returned to the detector after the primary pulse has ended.
-
Signal analysis:
- PI detectors measure the amplitude and timing of received signals. Based on how quickly the signal stops after the pulse is sent, it can be determined what type of metal has been detected. Different metals have different conductivity and magnetic properties, which affect the rate at which eddy currents decay.
-
Depth and sensitivity:
- PI detectors are able to detect objects significantly deeper than VLF detectors due to their ability to ignore soil mineralization and concentrate only on the products of eddy currents from metals.
Advantages and limitations of PI detectors:
-
Advantages:
- Great depth of detection.
- High resistance to soil mineralization.
- Effective in salt water where VLF detectors often fail.
-
Limitations:
- Lower discriminating ability compared to VLF detectors. PI detectors may have difficulty discriminating between different types of metals and often detect more false signals from unwanted metals.
- Typically more expensive and heavier than VLF detectors.
PI detectors are ideal for beach searches, underwater detection and in areas of high mineralization where other types of detectors may not be effective.