Last updated: 13 Nov 12 @ 03:16  |  

Handy detection: hand-held metal detection technology can now detect even very small metallic objects

As correctional facilities struggle to control the influx of contraband smuggled into prisons, Robert Adams discusses how the latest generation of hand-held metal detectors can detect even tiny objects such as mobile SIM cards hidden in body cavities

The humble hand-held metal detector or, as it is sometimes affectionately called, the “hand wand”, is still one of the most effective and instantly recognisable security devices in use today. They are seen in so many places, from the local pub to the world’s busiest airports, and even in the odd TV drama. But are they fundamentally all the same, technology wise? Do they all work as well as each other? Do they all do the same job?

Going back to the 1960s, one of the very first fully self-contained, battery-operated hand held metal detectors (or HHMD for short) was a device called the Adams model B-100. It was considerably larger than today’s detectors (about the size of a small saucepan with a handle on the top) but it did a job which at the time that was unique: it detected metal objects (guns or explosive detonator devices) on a person and was mainly used by the army and military police.

The system worked on the now very dated beat frequency oscillator (BFO) technology principal, and made some very strange whining noises as it detected metal. After a couple of aircraft hijackings in the mid 1970s, the modern HHMD made its first steps into the gaze of the general public, initially at our major airports and looked like a “chrome ring” in appearance.

Many years on, in this high-tech world in which we live, much of the technology utilised in the standard “common-place” (low performance) search wands on the market has remained alarmingly unchanged, utilising technology such as induction balance, Pulse or even BFO. But some of the more innovative design and development manufacturers have made some major steps forward in the area of super high sensitivity metal detection technology, with further developments of continuous wave (CW). This technology principal enables the detection of very small amounts of metal at a much greater distance, making it ideal for the detection of objects that could be concealed deep inside clothing or even below skin tissue (ie body cavities) quickly and safely.

Perhaps one of the most challenging applications for this high sensitivity sensor technology is in the prison environment. The HHMD is commonly deployed in the prison environment to screen inmates for items that have been secreted either orally or in a body cavity, usually having been wrapped in tape or plastic first, then smuggled through secure areas undetected. These items range from hand cuff keys, razorblades, drugs wrapped in foil, hand fashioned weapons such as metal shanks, sharpened hacksaw blades, welding rods and many more. To detect these concealed items reliably and efficiently is difficult enough, even with today’s new generation of high sensitivity HHMD units.

Up until these specially designed high sensitivity units arrived in prisons, the only HHMDs available for this kind search procedure was the standard “airport” type of hand wands, which were really only designed to detect much larger and more general items such as handguns, knives and items you would expect to find on a passenger at an airport. So, in today’s very demanding prison environment, these hand wand devices were merely serving as a deterrent, with little or no effectiveness for the detection of very small metallic objects concealed in a body cavity of a prison inmate.

With the addition of a cellphone to the list of common smuggled contraband, the incarcerated individual now had the ability to run their criminal business affairs and have contact with the outside world relatively unhindered from their prison cell. Which obviously defeats the purpose of them being in prison in the first place. One US correctional technical committee member commented: “If we don’t have a method of detecting, jamming or removing cellphones from these inmates, we may as well set them free back on to the streets again”.

The US prison service was quick to embrace the original idea of the high sensitivity HHMD’s nearly 18 years ago. The California department of corrections and the Federal Bureau of Prisons initiated this change by steering away from the standard airport type hand wands and decided to trial this newly-developed high sensitivity HHMD with a much higher level of performance in some of the toughest prisons in the USA. It was immediately well received in the field by the prison guards, as this new detector was detecting and finding items on its first trial outing that had never been possible to detect before.

Word very quickly spread around other prison networks and a Technology Transfer Committee was formed (now very commonplace around the world) to share information of any new available technology innovations for prison applications. The smuggling and use of cellphones in prisons today has created a new and very real problem for prison staff worldwide, one that has demanded an even higher level of detection ability from the HHMD than ever before.

Permanent installation-type metal detectors alone, such as the BOSS chair or walkthrough archway type metal detectors were not successful alone, as they are not portable and lightweight enough for all scenarios. Adams Electronics started working on a new hand-held unit, as did one or two of the other more reputable metal detector manufacturers, in an attempt to detect these cell phones and its various component parts that were being concealed in body cavities, as this still seemed the most popular hiding place for such items.

One of the difficulties in detecting a cell phone is that they are often disassembled first in order to reduce the overall metal content of the phone, thus avoiding detection. Sometimes it is just the SIM card itself that is being passed through a security checkpoint. The SIM card has very little metal content, and what metal is present is largely of a nonferrous type, which some metal detector technologies find harder to detect than ferrous metal. So, to enable the detection procedure to be successful, this new and improved very high sensitivity HHMD had to be able to detect the SIM card by itself. It needed to be easy to operate, extremely sensitive to all metals (even to the tiniest pieces of metal) yet rugged enough to withstand constant daily use by a prison guard.

To tackle this problem for the British Prison service (MOJ), Adams developed a brand new model of HHMD. This detector is able to detect SIM cards and other various low metal content component parts of the popular range of cellphones, either fully constructed or disassembled. It utilises a further development to Adams own linear detection technology (based on the CW principal) which is able to measure and process even the minutest changes within the electromagnetic field of the detector’s search sensor, creating an overall performance that is highly sensitive but very user friendly.

This new HHMD was recently tested and evaluated in the UK for use in the British Prison Service, along with most of the other popular brands of HHMD on the market today. The (MOJ) contract was later awarded to Adams Electronics and its new super high sensitivity HHMD for this application due to its superior detection performance capability.

The HHMD still has a strong presence in many diverse applications today as a cheap, portable and easy-to-use security solution. Some sensor technology has made enormous progress in development and continues to do so. Making the users aware of this progress and of its value still remains very challenging, however, as many users see all HHMDs as more or less the same thing, which in fact they are most definitely not.

The more recent progress in super high sensitivity technology has enabled some of these devices to be capable of such high performance levels that they are being utilised by hospitals and other applications outside of security for their out-and-out ability to detect and locate tiny ingested metal objects below the skin tissue, without the need to perform an X-ray procedure. This new technology is quite clearly moving far away from the standard and now rather old-fashioned hand wand concept.

Surprisingly though, some imported versions of these old style hand wand devices are being sold to the professional security market today for as little as £25. Very often they have no proper safety testing and certification for use on people. If the person being scanned had a medically implanted device, it could be potentially life-threatening. They have an extremely poor level of performance, not being able to detect the expected basic objects reliably, and will often malfunction or break within just a matter of days of use. Unfortunately cost is always a significant and all-to-common reason why inferior products like this are purchased instead of professional quality equipment. But it is interesting to mention that even the most expensive professional quality HHMDs on the market today are still only just a few hundred pounds which, when you think of the unit’s portability, ability to detect concealed weapons, ease of use and reliability, still makes it a very cheap security solution compared to the nearest alternative installation type screening devices, which can have a starting price tag in the multiple thousands per unit.

Robert Adams is the owner of Adams Electronics and has been involved with the company since 1972. The company currently manufactures highly specialised high sensitivity metal detection equipment for the professional security industry.