Metal detectors come in a few different types, also known as detection technologies. Very low frequency, multi-frequency, and pulse induction are the three main types of detection technologies. Which type you should purchase depends on your needs and budget. You can find out more information by reading this article.
Very Low Frequency (VLF)
VLF is the most common type of metal detector and is almost always found on entry-level detectors under $1,000. This type of detector is built for the hobbyist and is excellent for coin, jewelry, and relic hunting. It’s not typically recommended for saltwater beach hunting, gold prospecting, or other types of detecting in highly mineralized ground.
They operate with a single frequency—typically between 3-20 kHz. Lower frequencies are best for old silver coins, whereas higher frequencies are best for smaller objects and lower conductivity metals like gold. Most VLF detectors will operate at 10-15 kHz, which is a happy medium for both types of treasure hunting.
It’s worth noting that many VLF metal detectors do not have adjustment ground balance controls, which is essential when detecting any type of mineralized ground. Instead, VLF detectors have a factory preset ground balance optimized for neutral ground where most beginners will do their detecting. Adjustable ground balance controls are typically only seen in detectors over $500.
Multi-Frequency metal detectors use a range of frequencies simultaneously. Their idea is to be the best metal detector for all types of targets in all kinds of environments. Indeed, they excel in areas of high mineralization as they have the unique ability to pound through the soil and ignore unwanted signals. Multi-frequency technology is typically only found in metal detectors with a price tag of $1k+.
Serious coin shooters swear by multi-frequency detectors and are convinced that they get superior depth than single-frequency VLF machines. In reality, the depth doesn’t change. What changes is the incredible discrimination and target ID of deeper targets like old silver coins. Because older coins have been in the ground so long, they’re found at greater depths. And the greater the depth, the harder it is for a VLF detector to decide what the target is. Sometimes a VLF will actually think it’s iron or some other form of trash, and the detectorist will walk on by. Someone will a multi-frequency detector would do wise to follow that person around and cherry-pick all the missed finds.
Their ability to perform in areas of high mineralization is particularly good for saltwater beaches. While any VLF detector will do fine on dry, white sand, they will not work well at all in black sand, wet sand, or in the water.
Minelab uses different forms of multi-frequency technology in their higher-end treasure hunting detectors. These include broad band spectrum (BBS), full-band spectrum (FBS), and multi-IQ. These machines are very powerful and consume a ton of battery life. To combat this, manufacturers use bigger, more powerful batteries, which can increase the weight of the detector.
Some companies will advertise their detectors as being multi-frequency when in fact, they have the ability to select from multiple single frequencies. There’s a significant difference between this and an actual multi-frequency machine that operates more than one frequency simultaneously.
Pulse Induction (PI)
Pulse induction is the last type of technology and is really only found in specialty detectors. Most people will not want or need to use a PI detector. PI metal detectors are most often used by serious saltwater beach detectorists and gold prospectors and have a steep learning curve. While multi-frequency detectors work well in mineralized soils and saltwater, they don’t compare to pulse induction when it comes to maximum depth.
PI detectors tend to look a bit different from other detectors. You’ll notice the coils are usually a single loop. That’s because these use a mono coil which essentially combines the transmitter and receiver coils allowing for maximum depth. While they punch deeper than any other detector, the disadvantage, of course, is that they do not discriminate well enough. This makes them unusable in urban areas and any area where there’s a lot of trash. I would not recommend using a PI machine for coin or relic hunting unless I was out in a very rural area.
Metal detectors come in all different shapes and sizes, with some variations providing more specialized capabilities than others. Choosing the right metal detector for your needs is essential to maximizing its performance. Which type of metal detector is best for you? The answer to that question depends on your needs and, of course, your budget!
Metal Detector Basics and Theory by Bruce Candy