How does pulse induction work?
When the current pulse to the coil stops, the magnetic field collapses. If there is a metal target in the ground, eddy currents form in it and the decay seen by the receiver fades more slowly. The software measures this difference with a sample taken a set time after the pulse: the longer the decay, the stronger the signal.
The PI method is preferred on mineralised ground and for deep search. In the HS Detector this cycle repeats 730 times per second.
Main page for this topic: HS Detector Mobile App
HS Detector signal chain
- Transmitter: MOSFET-driven TX/RX board, 120 µs pulse
- Sampling: sample point 15 µs after the pulse
- Coil: mono Ø33 cm (24 turns) or 2×2 m frame
- Power: 8 × 18650, 14.8 V Li-ion
- Output: dB signal, threshold comparison, depth, target type
Oscilloscope, threshold and depth
The oscilloscope in the app shows the pulse decay curve and the sampling point live; when a target is present the curve visibly lengthens. The signal is compared with a threshold; values above it are treated as a target and the speaker renders signal strength as a tone.
The depth estimate is calculated from the signal–depth relationship for the selected coil. For all screens, see the HS Detector mobile app.
For your own PI detector
If you are designing a PI detector, I cover timing, sampling and filtering on the board together with the display on the phone. Details: metal detector app development.
What I offer
730 Hz pulses
730 measurement cycles per second
120 µs TX
Short, strong transmit pulse
15 µs sample
Decay point measurement
Oscilloscope
Live decay curve
Threshold and tone
Signal strength as sound
Depth estimate
Calculated per coil
Technologies I use
How we work
Free intro call
We clarify needs, existing systems and goals together.
Quote & roadmap
Scope, technology, timeline and budget within 24 hours.
Staged development
Weekly demos and a live test environment.
Launch & support
Go-live, training and ongoing maintenance.
Free pre-analysisThe first meeting and roadmap are completely free, with no obligation.
Staged delivery and approvalYou review each module on a test environment before we move on.
Written scope and rightsScope, delivery and source code rights are defined in the contract.
Frequently asked questions
What is a pulse induction detector?
A detector that sends short current pulses to a coil and measures the magnetic decay after the current stops; preferred on mineralised ground and for deep search.
What is the HS Detector's pulse rate?
The coil fires 730 pulses per second; the transmit pulse is 120 µs and sampling is at 15 µs.
What does the oscilloscope screen show?
The pulse decay curve and the sampling point, live; when a target is present the decay visibly lengthens.
How is depth estimated?
From the relationship between signal strength and depth, for the selected coil type.