H. Prance

An ultra-low-noise electrical-potential probe for human-body scanning

In this paper we describe a new very-low-noise, high-input-impedance probe developed to make non-contact measurements of electrical potentials generated by currents flowing in the human body. With a noise level of 2 µV Hz-1/2 at 1 Hz, down to 0.1 µV Hz-1/2 at 1 kHz, and an operational bandwidth from 0.01 Hz to 100 KHz, this probe would seem well suited to the detection of a wide range of electrical activity in the body.

Remote detection of human electrophysiological signals using electric potential sensors

We describe the measurement of human electrophysiological and movement signals remotely from a seated subject. An ultrahigh impedance electric potential sensor, designed specifically to reject external noise, is used to measure the electric field at distances of up to 40cm from the surface of the body. The sensor is able to provide continuous data acquisition, at full sensitivity, without saturation by external noise sources. Respiration and heart signals are seen simultaneously and are separated using digital filtering techniques. All of the results reported were obtained in an open unshielded environment in close proximity to line operated computer equipment.

Non-contact VLSI imaging using a scanning electric potential microscope

We describe the design and use of a novel scanning microscope which detects changes in electric potential above a surface. We demonstrate that this can be employed to image integrated circuits of considerable complexity in various modes of operation and at a spatial resolution of m. We discuss the advantages of applying this imaging technique to the non-invasive evaluation of very large scale integrated circuits and consider possible limits to its resolution and sensitivity in this role.

Compact room-temperature induction magnetometer with superconducting quantum interference device level field sensitivity

In this article, we describe significant developments in the design and construction of robust and compact room-temperature induction magnetometers with magnetic field sensitivities comparable to those usually associated only with superconducting quantum interference device (SQUID) magnetometers operating at cryogenic temperatures. In this system, we make use of both temperature independent amorphous magnetic core materials and ultralow noise signal processing electronics to achieve a spot noise figure of 14?fT/ at 300 Hz measured in a specially constructed, very low field environment. We present results over an operating bandwidth of 30 mHz to 3 kHz and show that linearity is preserved over almost six decades in an applied magnetic field amplitude. We compare the spectral noise of our systems with recently published data on SQUID magnetometers.

Ultra low noise induction magnetometer for variable temperature operation

Abstract In recent publications, the authors have reported on the performance of compact broadband induction magnetometer systems with an operating bandwidth from 100 μHz to 1 MHz. The best room temperature noise performance achieved was ∼500 fT/√Hz from 10 kHz to 1 MHz. In this paper, we describe improvements to the coil design and signal processing electronics, which result in a further reduction of the noise (∼50 fT/√Hz, in the range 1–30 kHz). In addition, we have chosen a magnetic material with a very small temperature dependence allowing us to investigate whether a reduction in noise may be achieved by operating the system at a reduced temperature (77 K).

Barrier traversal time in the quantum potential picture

We discuss the time taken for a particle to pass through a classically forbidden barrier in the quantum potential approach to quantum mechanics.

Compact broadband gradiometric induction magnetometer system

Abstract In this paper we describe two versions of a compact broadband ferrite based induction magnetometer system which span an operating bandwidth from 1 mHz to 1 MHz. In order to produce this compact system it was necessary to consider both the design of the pick up coils and the signal processing electronics. Here, we present an alternative to the traditional analogue integrator technique and conclude that this leads to significant advantages in bandwidth, long term stability and weight of the coils.

The Josephson pendulum as a nonlinear capacitor

In the quantum electrodynamic circuit theory of weak link constrictions, the singly connected weak link exhibits energy bands in charge space. Here, it is shown that charge space energy bands arise also in the quantum mechanical treatment of a Josephson pendulum.

Adaptive Electric Potential Sensors for smart signal acquisition and processing

Current applications of the Electric Potential Sensor operate in a strongly (capacitively) coupled limit, with the sensor physically close to or touching the source. This mode of operation screens the sensor effectively from the majority of external noise. To date however the full capability of these sensors operating in a remote mode has not been realised outside of a screened environment (Faraday cage). This paper describes the results of preliminary work in tailoring the response of the sensors to particular signals and so reject background noise, thereby enhancing both the dynamic range and signal to noise ratio significantly.

Sensor Developments for Electrophysiological Monitoring in Healthcare

Recent years have seen a renewal of interest in the development of sensor systems which can be used to monitor electrophysiological signals in a number of different settings. These include clinical, outside of the clinical setting with the subject ambulatory and going about their daily lives, and over long periods. The primary impetus for this is the challenge of providing healthcare for the ageing population based on home health monitoring, telehealth and telemedicine. Another stimulus is the demand for life sign monitoring of critical personnel such as fire fighters and military combatants. A related area of interest which, whilst not in the category of healthcare, utilises many of the same approaches, is that of sports physiology for both professional athletes and for recreation. Clinical diagnosis of conditions in, for example, cardiology and neurology remain based on conventional sensors, using established electrodes and well understood electrode placements. However, the demands of long term health monitoring, rehabilitation support and assistive technology for the disabled and elderly are leading research groups such as ours towards novel sensors, wearable and wireless enabled systems and flexible sensor arrays.