Metal Detector Discrimination Explained: When to Use It and When Not To

Metal detector discrimination is a setting that tells the detector to ignore, or give a different sound for, targets whose signal looks like iron or common trash. Used lightly, it saves time on junk-heavy sites. Used heavily, it can make you walk past gold rings, nickels, small nuggets and relics, because many valuable targets read in the same range as trash.

This guide explains how discrimination works, the difference between discrimination and notching, when to rely on it and when to switch to all-metal and dig everything.

How metal detector discrimination works

A typical VLF (very low frequency) detector transmits a continuous magnetic field and listens for the response from metal objects. Different metals and object shapes shift that response in characteristic ways. Highly conductive targets such as large silver or copper coins respond differently from small, thin or less conductive targets such as foil, small gold or thin jewelry. Iron produces its own distinctive response.

The detector converts that response into a target ID number and, usually, a tone. Discrimination simply tells the machine to stay silent, or to give a low "iron" tone, for IDs you choose to reject. Our guide on reading metal detector target IDs covers the ID scale in detail.

The key point: discrimination does not identify metal type directly. It classifies a signal. Target size, shape, depth, orientation, corrosion and ground mineralization all affect that signal, which is why discrimination is never perfectly reliable.

Types of discrimination

Variable (threshold) discrimination

The simplest type: you set a level, and every target reading below it is rejected. Turn it up and you reject iron first, then foil, then pull tabs and so on. It is quick to set but blunt, because everything in the rejected range is lost.

Notch discrimination

Notching lets you reject specific segments of the ID scale while accepting those on either side. For example, you might notch out a range where pull tabs commonly read while still accepting foil-range and nickel-range targets. Notching is more precise but still imperfect, because the range you notch out also contains some good targets.

Iron discrimination and iron audio

Many detectors offer a separate iron rejection or "iron volume" setting. Instead of silencing iron, you can turn its tone down so you still hear it as a low grunt. This is often the best compromise: you know iron is there, and you hear when a good target sits next to it.

All-metal mode

All-metal mode accepts everything. It usually gives the most stable response to faint, deep signals and is the standard mode for gold prospecting and many relic hunters.

What discrimination can cost you

Every time you reject a range of IDs, you reject everything that reads there, good or bad.

• Gold jewelry. Many gold rings, especially small or thin ones, read in the same range as foil, pull tabs and bottle-cap fragments. Heavy discrimination rejects many of them.
• Nickels. US nickels typically read in the foil-to-pull-tab range on many machines.
• Small gold nuggets. Small natural gold often reads low, sometimes close to iron, especially in mineralized ground. Prospectors usually dig everything.
• Relics. Lead, thin brass, buttons and buckles can produce mixed or unexpected IDs.
• Deep targets. The deeper the target, the less reliable its ID. A deep silver coin can read inconsistently, and some machines may reject it on some swings.
• Targets masked by iron. When a good target sits close to a nail, the detector may see mostly the nail. Heavy iron rejection silences the whole signal, and the good target goes with it.

Aluminum deserves its own mention: aluminum trash and gold can overlap heavily on the ID scale. Our article Can a Metal Detector Detect Aluminum? explains why.

When to use discrimination

Discrimination is a time-management tool. It makes the most sense when there is more trash than time.

• Heavily littered parks and schoolyards, where digging every pull tab would mean recovering only a fraction of the site.
• Tot lots and beaches with heavy foil, where light discrimination of the lowest foil range can help, at the cost of the smallest jewelry.
• Old home sites carpeted in nails, where some iron rejection or iron audio keeps you sane, provided you slow down so non-ferrous targets between the nails still come through.
• Coin-focused hunting, where you have decided to target higher-conductive coins and accept the trade-off.

When not to use discrimination

• Gold prospecting. Most prospectors run all-metal and dig every repeatable signal, because small nuggets and hot rocks overlap. A discrimination setting can reject the very gold you came for.
• Jewelry hunting. If you are looking for rings, you have to dig foil-range and pull-tab-range targets.
• Relic sites with low trash. When signals are scarce, each one is worth investigating.
• Searching for a specific lost item. If you know what was lost, discriminate only what it definitely is not.
• Deep target hunting. Faint, deep signals are the most likely to be misidentified.

Discrimination settings by situation

How to set discrimination: a practical checklist

1. Start in all-metal or with discrimination at zero to hear what the site sounds like.
2. Note what you are digging. If 9 of 10 targets are the same type of trash, consider rejecting that range.
3. Prefer iron audio or a low iron tone over complete iron rejection.
4. Use notching instead of a blunt variable setting where your detector allows it.
5. Test your settings on known targets: a gold ring, a nickel, a pull tab, a nail.
6. Slow your swing in iron-heavy ground so the detector can separate targets.
7. Re-check rejected signals from a different direction if they sound promising.
8. Revisit your settings each time you move to a different site or soil.

Tones as an alternative to discrimination

Many modern detectors let you hear iron as a low tone and non-ferrous targets as higher tones, instead of silencing anything. This "listen, don't reject" approach gives you more information and is preferred by many experienced detectorists. Learning what a good target sounds like among trash takes practice; our guide to metal detector tones walks through it.

Discrimination on pulse induction and multi-system detectors

Pulse induction (PI) detectors generally offer limited or no conventional discrimination. They are valued for depth and for handling mineralized ground and salt water, but they usually make you dig more trash. See pulse induction vs VLF for the full comparison.

Some professional multi-system detectors include VLF modes with adjustable discrimination. The manufacturer of the UIG Gold Digger, for example, lists a customizable metal discrimination system on its VLF platform. Long-range and imaging systems often advertise "metal type" selection as well; treat those as manufacturer-stated capabilities and confirm targets with a conventional coil or pinpointer before relying on them.

Frequently asked questions

Does discrimination reduce detection depth?

It can reduce your effective depth on some machines, because faint deep signals are the most likely to be misread and rejected. Running minimal discrimination is a common approach when depth matters.

Should beginners use discrimination?

Light discrimination or iron audio helps beginners stay motivated on trashy sites. It is still worth digging everything for the first few sessions to learn what different targets sound like on your machine.

What is the difference between discrimination and notch?

Variable discrimination rejects everything below a set point. Notching rejects specific ID segments while accepting targets on both sides of them.

Why do I keep digging trash even with discrimination on?

Because trash and good targets overlap on the ID scale, and because depth, orientation and nearby iron all distort IDs. No discrimination system is perfectly selective.

Should I use discrimination for gold nuggets?

Most prospectors do not. Small nuggets can read close to iron or hot rocks, so all-metal mode and digging every repeatable signal is the standard approach.