Sensor Signal Conditioning Research Articles

Signal conditioning for semiconductor gas sensors being used as detectors in gas-chromatographs and similar applications

The ability of feedforward neural networks to approximate the dynamic behavior of linear and non-linear sensors was investigated. The networks were trained with data from simulated and real systems to compute the time varying sensor input from the measurable sensor output. Characteristic curves describing the static and dynamic network properties were calculated. The network performance was tested and visualized in time and frequency domain (Bode diagram). It is shown that feedforward neural networks are an appropriate tool to approximate the dynamic behavior of non-linear gas sensors.

Pressure-tolerant network interface cards for sensor arrays

Pressure-tolerant ATM and Ethernet network interface cards (NICs) were developed for towed array data acquisition and telemetry. The card functions include sensor signal conditioning, analog-to-digital conversion, network protocol processors, and network interface transceivers. Design and fabrication techniques were developed to achieve space constraints, power constraints, and operation at 2500-psi pressure in oil or saltwater submersion without the use of pressure vessel housings. The development included the testing of candidate electronic components and NIC assemblies for pressure, temperature, and oil tolerance. Components and assemblies which failed testing were analyzed, and design rules were established for future designs. Generally, the elimination or minimization of voids by proper component selection and fabrication was found to be critical. Pressure-tolerant fabrication techniques were developed such as temperature cycle screening, encapsulation in low-viscosity polyurethane, pressurized curing, and compression sealed wires. High-density printed circuit boards and minimalist circuit designs were used to minimize NIC size. Low-voltage components, selective component location, and thermally conductive packaging were used to minimize operating temperatures. Commercially available components and open standard interfaces were used to minimize costs.

Characterisation of silicon carbide JFETs with respect to microsystems for high temperature applications

In this work first commercially available SiC-transistor prototypes were tested with regard to their applicability in high temperature electronic circuits for sensor signal conditioning.

Considerations for the design of smart sensors

This paper discusses considerations which must be made during the design of a smart sensor. The points raised are based on experience gained during the design of a mixed signal ASIC for smart sensor applications. Reference is made to the circuitry required for such a design, the level of integration implemented and the design methodology used. The discussions highlight the difficulties in integrating all of the functions needed for a smart sensor signal conditioning on a single piece of silicon.

Electronic odour sensing systems

An odour sensing instrument has been developed and used to classify many different materials, including beers, spirits and alcohols. The next stage in development is to begin to relate subjective odour descriptors (e.g. fruity, minty) to quantitative sensor array measurements. This task is being approached using both neural network and multivariate statistical techniques. The ultimate goal is to provide a measurement standard for odours. This exciting prospect requires the integration of sensor technology, signal conditioning, data acquisition and pattern recognition.

Adaptive signal conditioning for limiting-current type sensors

A ZrO 2-based solid electrolyte cell, provided with a diffusion barrier on the cathode side, can be used for measuring oxygen concentrations in the range between ppm and percent. If a voltage U p is applied to such a sensor device with a diffusion-controlled characteristic, the current in this circuit is proportional to the oxygen concentration. For its application a complex signal-conditioning system is necessary. The components of such a unit, for example the analog to digital converter (ADC) or the control for the pumping voltage, are described. It is necessary to combine this hardware structure with an efficient signal-processing algorithm to calculate the relevant sensor and process information. Such a unit has been designed and built and its performance is reported.

A Compact Portable Data Acquisition Module for Sports Biomechanics Research

This article describes a new portable digital data acquisition module, which has been developed for the measurement and temporary storage of signals from mobile biomechanical phenomena in the field. The module’s performance capabilities include 32 available analog input channels, a 12-bit analog-to-digital converter, maximum throughput of 57,040 samples per second, and a temporary storage capacity of up to 253,000 samples. The portable power source is a rechargeable battery pack, and the appropriate sensors and sensor signal conditioning circuits are supplied by the user to meet the particular needs of the phenomena under study. The size of the signal conditioning, battery pack, and data acquisition module is such that it can be carried in a belt pack worn by a subject under study and weighs less than 3 kgf. To facilitate the use of the module, operating software complements the hardware. The software is comprehensive functionally in that routines are provided for acquiring data, for transferring acquired data serially to a general purpose microcomputer for storage on magnetic media, and for monitoring equipment setup. Further, the software is versatile in that the various parameters necessary to customize the operation to a particular application may be readily set. Finally, the menu-driven structure ensures that the software is easy to use.

Analog circuit for interfacing silicon optical sensors and driving a dual-slope A/D converter for logarithmic read-out

State-of-the-art A/D converter research is usually focussed on either increasing the resolution or the speed of linear A/D converters. However, in many data acquisition systems input transducers, such as LVDT displacement sensors, pressure sensors, photodiode optical sensors or magnetic-field sensors, are used with a dynamic range exceeding four decades and an inaccuracy of around 1%. This common practice favours nonlinear quantizing, which features a constant relative accuracy, rather than the implementation of a linear A/D converter in which the specifications with respect to resolution and accuracy would lead to an undesirable price/performance ratio. The nonlinear A/D converter for the read-out of a photodiode, that is discussed here, is based on the combined operation of a special analog circuit and a moderate-resolution dual-slope linear A/D converter. The analog circuit has been designed to serve as an interface between a photodiode and a commercially-available dual-slope A/D converter and supplies such currents to the dual-slope integrator that a dual-slope counter content is available after conversion proportional to the logarithm of the photocurrent. The combined analog chip with sensor and analog signal conditioning circuits and the dual-slope converter form a dual-chip smart integrated silicon optical sensor with a reading between 00.0 and 99.9 dB.

Sensors with digital or frequency output

Most sensors are based on elements of which one of the parameters (resistivity, dielectric constant, Hall voltage, signal frequency, etc.) shows a small change in response to one or more measurands. To apply sensors is a system, an intimate knowledge of the working of the sensor element is usually necessary. The new age of sensors has come about with the development of planar silicon (and GaAs) technology, permitting the integration of sensor elements and signal conditioning circuitry on one chip. This approach might eventually lead to a family of sensors with a microprocessor-compatible output as shown in Fig. 1, which can easily be applied in bus-organized data-acquisition systems [1, 2]. An intermediate and necessary step to reach this ambitious goal is the design of sensors with a digital or frequency output. In this paper the most important techniques and structures are reviewed.

Integrated signal conditioning for silicon pressure sensors

A silicon-diaphragm pressure sensor containing on-chip circuitry for signal conditioning has been designed for applications in biomedicine. The device requires no off-chip components and only two external leads, making it suitable for use with multisensor catheters having diameters less than 1.5 mm. The output is a temperature-compensated high-frequency FM analog representation of the applied pressure signal. The device exhibits 1-percent resolution and accuracy over the physiological pressure and temperature ranges. Circuit techniques applicable to a variety of active sensors are descried.