by Michael Bernzweig

Understanding Metal Detector Sensitivity

The sensitivity setting on a metal detector affects how deep into the ground the device can detect a target object. Read this article to learn more about what the sensitivity control can do for you. Understanding metal detector sensitivity levels is a key part of getting the most out of your metal detector. By understanding your metal detector sensitivity, you will understand how to be adjust your device to make it a super sensitive metal detector.

Sensitivity is the measure of a device's ability to detect certain types and sizes of metal targets or in some situations metal contaminants in a finished good. The higher the sensitivity of your metal detector, the smaller the pieces of metal you will find. Performance is often shown in terms of the diameter of a specific type of metal. These metals include ferrous, non-ferrous, aluminum, or stainless steel. The more sensitive your metal detector is, the smaller the pieces of metal you will be able to detect.

Sensitivity is important for metal detectors. Not only does it allow you to find specific metals, but it can prevent you from digging in specific situations that might prevent dangerous situations. For example using an industrial metal detectors utility locating  can prevent someone from digging an area in which underground pipes have been laid. Metal detectors used in manufacturing environments such as lumber mills and other production environments need to have the right aperture size and target position. The smallest aperture size will maximize sensitivity. For conveyor inspection, the aperture size will also depend on product dimensions and orientation.

How Metal Detector Sensitivity Is Measured

The sensitivity of a metal detector is measured using a test piece. The test piece must be detectable when it is passed through the center point of the metal detector's coil. A number of issues can alter the sensitivity of a metal detector. 

A metal detector's sensitivity is sometimes referred to as its gain control. Your metal detector's gain control determines how deep it penetrates the earth. To find the right setting, you have to experiment. There may be an auto-sensitivity option on your device.

Set the sensitivity manually by increasing the device's sensitivity or gain until interference is detected. Once interference is detected, turn the device down to receive more accurate signals. Metal signals will be more obvious than signals for other materials.

What Factors Affect the Sensitivity of a Metal Detector?

There are a few factors that affect the sensitivity of a metal detector. These factors can be frustrating for detectorists and lead you on a wild goose chase. It is important to understand that setting the sensitivity of a metal detector on high and digging everything you find is not a wise tactic. In fact, many metal detectors ship with the preset sensitivity set higher than it is possible to use in many situations. 

Orientation Effect

For example, in manufacturing situations, the ability of a metal detector to detect non-spherical contaminants such as wire or swarf is somewhat determined by the metal contamination type, such as ferrous metals, non-ferrous metals, or stainless steel. Metals of different types have an effect on the accuracy of a device's ability to locate treasures.

In addition, the metal object’s orientation plays a role in the device's ability to detect it. In our manufacturing example, we are able to observe the orientation effect when the diameter of the metal contaminant is less than the spherical sensitivity of the device.

Environmental Conditions

A metal detector’s factory preset settings can alter its performance for metal detecting the field. Noise and vibration immunity is of utmost importance in industrial and underground pipe locating applications. It minimizes airborne interference and vibration in the plant. The two items can affect a metal detector's sensitivity. Even the packaging the metal detector came in can affect its sensitivity in extreme situations.

Mineralization

Mineralization can cause interference with the device's sensitivity when particles in the soil contain metal-like characteristics. Electromagnetic fields produced by ground minerals can cause your device to respond. Old soil that has been on the surface of the Earth for a long period of time is the ground most likely to give you a false reading. Rain pushes iron to the surface of the ground. Ground mineralization is a nightmare for many detectorists. So, rather than finding coins, you may simply locate mineralized soil. These false signals can be maddening and cause you to spend valuable time digging for nothing.

How to Set the Sensitivity on a Metal Detector

To manually set the sensitivity:

1. Turn up the device's sensitivity, or gain until there is interference. 
2. Then, turn it down until you receive more accurate signals. 
3. Finally you will notice that the signals for metal will be obvious compared to the signals for other materials.

You should not keep the device's sensitivity setting too high. This isn't going to help you detect more items and artifacts. By turning the metal detector's sensitivity all the way up, you would naturally believe you will find more treasure. However, this simply isn't true. The higher the sensitivity, the more likely you are to trigger unwanted pings and responses. You could get responses from local radio stations, mineralization, or even cellphones with a maximum sensitivity setting. The metal detector's chances of responding to these items are greater if the sensitivity is turned up high. 

Finding the correct sensitivity setting takes time and you are likely to experiment with the device to find it. Your device may have an auto option allowing you to quickly set the sensitivity. Stability is a key factor for sensitivity. If you receive a stable signal, then you are likely in the correct setting. You should be able to hear if the signal is not stable. Once again, experiment with your device's sensitivity. However, putting it on as high as possible and digging up everything is a waste of your time. 

Auto vs. Manual Sensitivity

By setting your metal detector's sensitivity on auto, your device will measure the ground. It will also set the device's sensitivity to the highest stable setting available. You should have success with the auto setting, but you may have an issue when you walk across conductive ground that contains a high salt content.

If you regularly search beaches, you may run into issues with your detector's ability to filter out minerals and locate targets at greater depths. Saltwater beaches are conductive ground and you may get unwanted responses. An auto detection sensitivity setting may give you inconsistent readings along with an incorrect setting. Of course, the opposite could also occur when metal detecting on conductive ground.  By adjusting your discrimination and ground balance controls in conjunction with your sensitivity you will be able to better filter out the impacts of the environment. Metal detector frequency plays a roll in reducing the interference as well. You might explore a model that offers a simultaneous frequency setting, sometimes referred to a Fast Multi Frequency (FMF) or metal detector or a Simultaneous Multi Frequency (SMF).

Manually setting the sensitivity on your metal detector takes more time to get right as opposed to using the auto setting. The type of metal detector can also play a part in the time it takes to adjust the sensitivity. Always be sure to wear your headphones when setting the sensitivity. If you test the ground and continually increase the sensitivity of the metal detector, you should get a more accurate setting. You should raise the sensitivity until you receive feedback and inconsistent responses. Once this occurs, lower the sensitivity a little bit. It may take a little time to reach the proper setting, however, you will be more successful in the long term when hunting for treasure at depth.

Copyright 2021 Detector Electronics Corp.