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Steve Herschbach

Waterproof Pulse Induction Detectors Compared

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The waterproof pulse induction field is very limited at this time. It divides into two classes. Pulse induction metal detectors that ground balance, and those that do not.

A pulse induction (PI) detector by its nature tends to ignore mineralization, so much so that in milder conditions a PI works fine without a ground balance circuit. As I noted above however a PI is not immune to mineralization. A non-ground balancing PI detector will sound off when raised and lowered over true black sands. The more concentrated the magnetite, the more intense these signals will be. The bottom line is that on real bad black sand beaches even a basic pulse induction will sound off if the coil height is varied too rapidly over the beach. In the water with troughs and depressions false signals are all but impossible to avoid. The most extreme situations require a ground balancing pulse induction (GBPI) metal detector.

  1. Pure white non-magnetic coral beaches - most any detector will work well
  2. Even a hint of mineralization - a multifrequency detector has an edge over single frequency VLF where there are both saltwater and magnetic minerals.
  3. Moderate mineralization - you want multifrequency or pulse induction.
  4. Severe mineralization - at some point a ground balancing PI (GBPI) is required.

The above conditions grade from one into the other seamlessly. Hot rocks are a wild card as hot rocks in a normally mild beach can cause false signals on a PI detector that lacks ground balancing capability.

Finally, I should note that PI detectors with ground balancing capability have a crude sort of tone discrimination that can be used to advantage.

Fully submersible pulse induction metal detectors

Here are the current mainline waterproof PI detector offerings:

Bounty Hunter - no PI
Garrett - Sea Hunter Mark II (PI) and ATX (GBPI)
Fisher - Impulse AQ
Minelab - SDC 2300 (GBPI)
Nokta/Makro - no PI
Teknetics - no PI
Tesoro - Sand Shark (PI) (Discontinued)
White's - Surfmaster Dual Field (PI) and TDI BeachHunter (GBPI)
XP - No PI

Finally, here are the key specifications for comparison:

Fully submersible pulse induction metal detectors


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Some short personal opinions:

Garrett Sea Hunter Mark II - Well proven detector waterproof to 250 feet, optional coils, killer price. It is on the heavy side but it can be hip mounted. The only real downside is that as a non-ground balancing PI it can react to black sands and hot rocks. But for normal beach detecting I'd recommend the Sea Hunter for somebody wanting a non-ground balancing PI. It's a real bargain at $649 and with interchangeable coils.

Garrett ATX - Ground balancing PI in industrial strength housing. White's TDI Beachhunter has a saltwater beach edge with it's "ground balance off" setting. ATX is the better of the two if ground balance is engaged. The ATX is a dual channel PI whereas the TDI is a single channel PI, which means there is a huge "hole" near the ground balance setting where gold in the 1/4 ounce range is very weak. This also means the ATX is the better prospecting machine. The ATX is expensive, heavy, and suffers from coil cable and rod issues with exposure to sand and saltwater. I did well with the ATX on the beach but that was before the TDI Beachhunter came out. I'd now recommend the TDI instead unless you really needed the coil options.

Fisher Impulse AQ - New model promises light weight and superior performance with ground balance on or off. All is speculation until more is known, but unless you need a waterproof PI detector right now, wait a bit for this one.

Minelab SDC 2300 - Looks good on paper. Extremely sensitive to small items for a PI, and therefore superb on small gold nuggets. But in water it floats like a cork, and it is very expensive. Waterproof integrity is worrisome for such an expensive detector. The hardwired 8" mono limits ground coverage on large beaches. As a result you won't see many of these at the beach.

Tesoro Sand Shark - Was not a bad unit but with Tesoro out of business - stay away.

White's Surfmaster Dual Field - Excellent non-ground balancing PI, solid performer, easy to operate. A lighter weight alternative to the Sea Hunter above, but also more expensive and with a hardwired coil. Note that the Surfmaster does have twice the warranty of the Sea Hunter.

White's TDI BeachHunter - Good performance in ground balance off mode, top notch if battery replaced with higher voltage option (see White's Forum). Good ground balance option but does have a weakness on certain heavy gold rings. The weakness goes away in the ground balance is turned off. For $1199 this is really the only decent proven option in a waterproof ground balancing PI at the moment until more is known about the Impulse AQ.

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The Garrett Infinium is the less powerful predecessor to the ATX. But at least it is in a lighter package with coils not priced to the moon. It is also one of the least reliable metal detectors I ever owned, both for coil and control box failures. I owned at least six Infiniums personally and for my pay-to-mine operation, and I don't recall even one that did not eventually fail and have to be returned to Garrett. Great little detector actually and I did very well with mine, but I'd be shy of a used one simply because of my bad luck with the reliability.

The Infinium has no "ground balance off" setting and is always in ground balance mode. The TDI has a very distinct advantage there.


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1 hour ago, Steve Herschbach said:

The Garrett Infinium is the less powerful predecessor to the ATX. But at least it is in a lighter package with coils not priced to the moon. It is also one of the least reliable metal detectors I ever owned, both for coil and control box failures. I owned at least six Infiniums personally and for my pay-to-mine operation, and I don't recall even one that did not eventually fail and have to be returned to Garrett. Great little detector actually and I did very well with mine, but I'd be shy of a used one simply because of my bad luck with the reliability.

I won't hip mount it anymore   because of all the coil  problems it had when I did  in water.

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On 6/2/2020 at 3:40 AM, Dances With Doves said:

 How would you compare the beach tdi with the infinium for depth?

I have used both units....From my in ground tests and records, the TDIBH is clearly superior in depth. A 12” target seen by the Infinium will be seen at 15” with the TDIBH running the higher voltage pack. The stock TDIBH battery will still have a clear advantage over the Infinium. I used to also run a Garrett Sea Hunter MK2 and it pipped the Infinium in depth......straight PI over the GBPI won out (in white coral sands).

Currently......the TDIBH @ 14.4v is as deep as you will get from any detector (for typical beach hunting) including any PI from Minelab. I don’t have to deal with any magnetic black sands locally. I’d like to test out the TDIBH in true black sands with GB on.

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I’ve always wondered why the PIs have to be so heavy!

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Usually it has been because they have been made for scuba diving depths, and so required very heavy housings. There have been very light weight PI detectors designed, like the DetectorPro Headhunter Pulse (no longer made). It’s not that hard if you are designing a lower power PI, and in fact we have had PI pinpointers for many years. The Headhunter started as a headphone based pinpointer design.

High power PI units rely on very powerful batteries, so that’s been the other issue. Most Minelab PI detectors use a separate belt mounted battery the size of a brick. Getting powerful batteries that are safe and reliable for underwater use has been a major challenge, and one not really solved to anyone’s satisfaction yet.

DetectorPro Headhunter Pulse

Operating Search Frequency: Pulse Induction
Searchcoil: 11“ Round, Open-Center
Audio Frequency: Adjustable
Headphone Transducer: Piezo Electric
Search Mode: Slow Motion All-Metal
Operating Environments: Salt water, Fresh water
Submersible: Waterproof to 6 feet
Length: Wading Configuration: 43 to 53“
Weight w/Batteries: 3.5 Pounds
Batteries: Two (2) 9V
Life: 6-10 hours
Warranty: 2 Years

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