Plessey to launch novel, high sensitivity electric field sensor

Citation

Bogue, R. (2011), "Plessey to launch novel, high sensitivity electric field sensor", Sensor Review, Vol. 31 No. 2. https://doi.org/10.1108/sr.2011.08731baf.001

Plessey to launch novel, high sensitivity electric field sensor

Article Type: Mini features From: Sensor Review, Volume 31, Issue 2

A sensor developed at the University of Sussex, UK, which was originally aimed at fundamental physics research is now being commercialised by Plessey Semiconductors and has the potential to satisfy a wide range of practical applications. Dubbed the electric potential sensor (EPS), this was developed by a team led by Robert Prance, Professor of Sensor Technology at the Centre for Physical Electronics and Quantum Technology at Sussex. According to Prance, in the 1950s, studies into low-voltage electric fields were driven by the development of photocopiers but since then, most research has concerned the fields associated with high voltages that might damage electronic equipment or involved the use of large, laboratory-based electrometers for lower voltage fields. However, his group was working on a “blue sky” research project in the 1990s involving quantum circuit behaviour at a temperature of −269 °C and needed an ultra-stable, non-contacting electric field sensor. A technique was subsequently developed and forms the basis of the EPS. It was developed further through the UK research councils’ Basic Technology Research Programme and a number of patent applications have been filed. The sensing element is a metal electrode which is coupled to ultra-high-input impedance (∼10¹⁴ Ω) circuitry, causing it to act as a high-sensitivity, non-contacting voltmeter which can detect very low electric fields. The prototype sensors, produced at Sussex, are the size of a small coin (Figures 1 and 2) and Plessey is now commercialising the technology. It will be using its in-house semiconductor processing expertise to replace the surface-mount circuitry used by the Sussex group with an integrated silicon system solution with appropriate microcontrollers and software.

Figure 1 Prototype EPSs

Figure 2 Prototype 16-element EPS array

The sensor requires no physical or resistive contact to make measurements and has potential in a variety of applications, ranging from healthcare and security to quality assurance and material testing. An interesting possibility is use by the emergency services which arises from the fact that most places on earth have a vertical electric field of about 100 V/m and as the human body is mostly water, this interacts with the field. EPS technology is sensitive enough to detect these changes at a distance and even through a solid wall. Thus, for example, in a fire situation, it could be possible to determine if there are people inside a smoke-filled room before opening a door.

Several of these applications have been investigated by the Sussex group which has already negotiated license agreements with a number of OEMs who will be bringing EPS-based products to market. Plessey anticipates early uses in medicine, where the sensors could detect the voltage changes associated with muscle and nerve activity in a non-contacting manner. This would allow the sensors to be used in a contactless electrocardiograph (ECG), where an array of EPS sensors could be located over a patient’s chest to obtain readings equivalent to a 12-lead ECG but without the wiring and electrodes that can easily become detached. With contact, it could be used in a twin-sensor ECG where one sensor is worn on each wrist to provide outputs similar to those from a standard ECG. Another application could be in electromyographs, where sensors detect nerve impulses and muscle contractions and could control artificial limbs from a simple pad on the surface on the skin. A further possibility is in electro-oculographs, where sensors on the head detect eye muscle movements. These data could be used in new man-machine interface devices for gaming or by the disabled. As no conducting gel is required, the sensors could be built into a pair of glasses which would locate them in a suitable position to obtain electro-oculographic readings. Plessey’s experience with the manufacture of CMOS image sensors will allow large area EPS arrays to be fabricated. These will allow 3D video images to be created, with each sensor effectively generating a pixel of information, which will open up further possible applications. Plessey expects to have the first product prototype available in Q3 of 2011 for a medical diagnostic product that will significantly advance the ease and quality of cardiac measurements.

Robert Bogue

Contacts

Plessey Semiconductors Ltd, Tamerton Road, Roborough, Plymouth, Devon, PL6 7BQ, UK. Tel.:+44 1752 693000, Fax: +44 1752 693200, web site: www.plesseysemi.com

Professor Robert Prance, Centre for Physical Electronics and Quantum Technology, University of Sussex, e-mail: R.J.Prance@sussex.ac.uk