Sensor Signal Conditioning Research Articles

Precision Analog Signal Conditioning Semiconductors for Operation in Very High Temperature Environments

When designing signal chains for systems exposed to high temperature environments, analog signal processing ICs are needed to enable precision sensor measurements. However, as ambient operating temperatures increase beyond the typical extended-industrial +125°C limit, the performance characteristics of analog semiconductors are strongly impacted by the effects of temperature on circuit design, packaging, and the underlying fabrication process. In this paper we introduce two new precision analog components, an operational amplifier and voltage reference, rated for very high temperature operation. We then discuss the steps taken to ensure their performance at high temperature is robust and can be maintained over a limited lifetime. Finally, we demonstrate these devices utilized in an example application: a constant current source for temperature sensor signal conditioning.

End of Life Failure Modes for Packaged SOI Devices for Signal Conditioning and Processing Applications

Silicon on Insulator (SOI) device technology has been shown to be capable of functioning satisfactorily at operating temperatures of >200°C. Most of the applications to date have required performance for short times (<2,000 hours) at the highest operating temperatures of up to 225°C in down-well drilling applications. There is interest in extending the endurance of high temperature electronics into aero-engine and other applications where a minimum 20 year operating life is stipulated. In order to gain confidence in high temperature electronics that can meet this requirement, accurate reliability data are needed and end of life failure modes need to be identified. Most of the reliability data on the high temperature endurance of the integrated circuit is generated with little consideration of the packaging technologies, whilst most of the reliability data pertinent to high temperature packaging technologies uses test pieces rather than devices, which limits any conclusions relating to long term electrical performance. This paper presents results of temperature storage and cycling endurance studies on SOI devices combined with high temperature packaging technologies relevant to signal conditioning and processing functions for sensors in down-well and aero-engine applications. The endurance studies have been carried out for up to 11,088 hours at 250°C, with functioning devices being tested periodically at room temperature, 125°C and 250°C and rapid thermal cycling from −40°C to +225°C. Different die attach and wire bond options have been included in the study and the performance of several functional blocks on the SOI device has been tracked over the endurance tests. The failure modes observed on completion of the endurance tests include die cracking and deterioration of the device bond pads accelerated due to degradation of some die attach materials. The routes to achieving stable long term performance of packaged devices at temperatures of 250°C will be outlined.

Realisation of High Temperature Electronics Packaging Technology for Sensor Conditioning and Processing Applications

The requirement to install electronic power and control systems in high temperature environments in aero-engines and in down-well exploration has posed a challenge to the traditional limit of 125°C of electronics systems. The leap in operating temperature to above 200°C in combination with high pressures, vibrations and potentially corrosive environments means that different semiconductors, passives, circuit boards and assembly processes will be needed to fulfil target performance specifications. Silicon on Insulator (SOI) device technology has been shown to be capable of functioning satisfactorily at operating temperatures of >200°C. Most of the applications to date have required performance for short times (<2,000 hours) at the highest operating temperatures of up to 225°C in down-well drilling applications. There is interest in extending the endurance of high temperature electronics into aero-engine and other applications where a minimum 20 year operating life is stipulated. Most of the reliability data on the high temperature endurance of the integrated circuit is generated with little consideration of the packaging technologies, whilst most of the reliability data pertinent to high temperature packaging technologies uses test pieces, which limits any conclusions relating to long term electrical performance. This paper will present results of studies on high temperature packaging technologies relevant to signal conditioning and processing functions for sensors in down-well and aero-engine applications. Different die attach and wire bond options have been included in the study and the performance of several functional blocks on a high temperature SOI device has been tracked over the endurance tests which have lasted for >11,000 hours at 250°C. Degradation phenomena such as thermal migration and material deterioration due to high temperature exposure in air and inert atmospheres will be described. An assessment of the availability of high temperature materials and components to meet long term requirements for operation at 250°C will be presented.

RANCANG BANGUN RANGKAIAN PENGKONDISI SINYAL UNTUK SENSOR DETEKSI KANDUNGAN NITRAT

Circuit Design for Sensor Detection Signal Conditioner Nitrate Content. Nitrate is one of macro nutrients very important for agriculture. The availability of nitrate in soil is limited because it is very easy to leaching by rain, therefore nitrate could be contaminated ground water by over-process of fertilizer. This process could also produce inefficiency in agriculture if it happened continuesly without pre-analysis of farm field. The answer those problems, it is need to develop the ion sensor system to measure concentrations of nitrat in soil. The system is consist of nitrate ion sensor device, signal conditioning and data acquisition circuit. The design and fabrications of signal conditioning circuit which integrated into ion nitrate sensor system and will apply for agriculture. This sensor has been used amperometric with three electrodes configuration: working, reference and auxiliarry; the ion senstive membrane has use conductive polymer. The screen printing technique has been choosen to fabricate electrodes and deposition technique for ion sensitive membrane is electropolymerization. The characterization of sensor has been conducted using nitrate standard solution with range of concentration between 1 µM–1 mM. The characterization has shown that sensor has a good response with cureent output between 2.8–4.71 µA, liniearity factor is 99.65% and time response 250 second.

CMOS Voltage-to-Frequency Converter With Temperature Drift Compensation

This paper presents a new complementary metal-oxide-semiconductor (CMOS) differential voltage-to-frequency converter (VFC) suitable for sensor signal conditioning. Designed in a low-cost 0.18- μm CMOS process, the proposed VFC consumes less than 0.4 mW at a 1.8-V supply. For a differential input range of 0-1.2 V, output frequency varies from 0.1 to 1.1 MHz with a linearity error of less than 0.4%. A new temperature compensation technique keeps the gain error below 2.4% over the whole frequency span for a range of -20°C- +120°C.

In-construction vibration monitoring of a super-tall structure using a long-range wireless sensing system

As a testbed for various structural health monitoring (SHM) technologies, a super-tall structure - the 610 m-tall Guangzhou Television and Sightseeing Tower (GTST) in southern China - is currently under construction. This study aims to explore state-of-the-art wireless sensing technologies for monitoring the ambient vibration of such a super-tall structure during construction. The very nature of wireless sensing frees the system from the need for extensive cabling and renders the system suitable for use on construction sites where conditions continuously change. On the other hand, unique technical hurdles exist when deploying wireless sensors in real-life structural monitoring applications. For example, the low-frequency and low-amplitude ambient vibration of the GTST poses significant challenges to sensor signal conditioning and digitization. Reliable wireless transmission over long distances is another technical challenge when utilized in such a super-tall structure. In this study, wireless sensing measurements are conducted at multiple heights of the GTST tower. Data transmission between a wireless sensing device installed at the upper levels of the tower and a base station located at the ground level (a distance that exceeds 443 m) is implemented. To verify the quality of the wireless measurements, the wireless data is compared with data collected by a conventional cable-based monitoring system. This preliminary study demonstrates that wireless sensing technologies have the capability of monitoring the low-amplitude and low-frequency ambient vibration of a super-tall and slender structure like the GTST.

High Temperature Endurance of Packaged SOI Devices for Signal Conditioning and Processing Applications

Silicon on Insulator (SOI) device technology is fulfilling a niche requirement for electronics that functions satisfactorily at operating temperatures of >200°C. Most of the reliability data on the high temperature endurance of the devices is generated on the device itself with little attention being paid to the packaging technology around the device. Similarly, most of the reliability data generated on high temperature packaging technologies uses testpieces rather than real devices, which restricts any conclusions on long term electrical performance. This paper presents results of high temperature endurance studies on SOI devices combined with high temperature packaging technologies relevant to signal conditioning and processing functions for sensors in down-well and aero-engine applications. The endurance studies have been carried out for up to 7,056 hours at 250°C, with functioning devices being tested periodically at room temperature, 125°C and 250°C. Different die attach and wire bond options have been included in the study and the performance of multiplexers, transistors, bandgap voltage, oscillators and voltage regulators functional blocks have been characterised. This work formed part of the UPTEMP project which was set-up with support from UK Technology Strategy Board and the EPSRC. The project brought together a consortium of end-users (Sondex Wireline and Vibro-Meter UK), electronic module manufacturers (GE Aviation Systems Newmarket) and material suppliers (Gwent Electronic Materials and Thermastrate Ltd) with Oxford University-Materials Department, the leading UK high temperature electronics research centre.

High Temperature Silicon Carbide CMOS Integrated Circuits

The wide band-gap of Silicon Carbide makes it a material suitable for IC's [1] operating up to 450°C. The maximum operating temperature achieved will depend on the transistor technology selected, interconnect metallisation and device packaging. This paper describes transistor and circuit results achieved in SiC CMOS technology, where the major issue addressed is the gate dielectric performance. N and p-channel MOSFET structures have been demonstrated operating at temperatures up to 400°C Test circuits including simple logic cells, ring oscillators, operational amplifiers and gate drive circuits have been fabricated and the characteristics of ring oscillators are presented here. Floating capacitor structures have also been fabricated for use in future analogue and mixed signal circuits. This technology will be initially applied in applications including signal conditioning for sensors and control of SiC based power switching devices, where the high temperature capability will match that of the SiC power devices which are now becoming commercially available.

USN응용과 범용목적에 적용가능한 센서 신호처리기

In sensor signal conditioning and processing, offset and drift characteristics of an operational amplifier are an important factor when the amplifier is used for a precise sensor signal amplifier. In order to use it in high accuracy, an expensive trimming or a complex compensation circuit is required. This paper presents the improved sensor signal conditioning and processing device for ubiquitous sensor network(USN) application or general purpose by developing a hardware of the circuit for reducing the offset voltage and drift characteristics, and a software for its control and sensor signal processing. We realize better offset voltage and drift characteristics of the signal conditioning circuit using low cost operational amplifiers. The experimental results show that this technique is effective in improving the performance of the sensor signal processing device.

An autonomous battery-less sensor module powered by piezoelectric energy harvesting withRF transmission of multiple measurement signals

An energy-autonomous battery-less sensor module is presented, entirely powered by apiezoelectric energy converter driven by mechanical vibrations from the environment.The module manages and stores the converted energy, interfaces to one or morepassive sensors and periodically sends the corresponding measurement signalsover a radio-frequency (RF) link. As an additional variant, the module can senda programmable identification (ID) code on the RF carrier, in order to enablemodule tagging and tracking by the external receiver unit. The module’s generalarchitecture is presented and the strategy used for sensor signal conditioning andtransmission is illustrated. The architecture and principle have been experimentallyvalidated on a fabricated prototype including a piezoelectric bimorph converter, twopassive sensors made by a resistive–capacitive sensor pair and purposely designedelectronic circuitry based on low-power off-the-shelf components. In the testedexperimental conditions, the prototype features a typical time interval betweenmeasurement-and-transmission events of a few tens of seconds, with event durations of theorder of tens of milliseconds, corresponding to an operation duty cycle of the order of 0.1%.Peak power consumption during transmission is of the order of 20 mW and operative rangeis of the order of meters in a laboratory environment. The obtained results showthat the proposed approach has attractive characteristics because of the totalabsence of batteries and, despite the inherent intermittent operation, providessignificant measurement performances in terms of achievable sensitivity and resolution.

Performance Tradeoffs of Three Novel GMR Contactless Angle Detectors

Three innovative solutions for contactless angle detection are described and compared. They use a giant magnetoresistive (GMR) sensor bridge which detects the direction of the magnetic field of a rotatable magnet placed near the sensor. The three solutions differ in the CMOS Application-Specific Integrated Circuit (ASIC) employed as sensor signal conditioning interface, leading to different cost-performance tradeoffs. The first ASIC is all-analog, being the simplest and cheapest one. The second ASIC is a mixed-mode solution providing a pulse width modulated (PWM) output, and its main innovation is the use of a compact piecewise-linear ADC to compensate for the sensor nonlinearity. This way, linearization and A/D conversion are performed simultaneously, saving power and silicon area. The third ASIC is mostly digital and fully programmable, being the most flexible and accurate (albeit costly) solution. It incorporates as main novelties a new offset compensation technique that shares most of required circuits with the successive-approximation ADC, and a new combinational circuit for linearization. Measurement results for the three implementations are provided, and their performance tradeoffs discussed.

Field data comparisons of MEMS accelerometers and analog geophones

Geophones have been the motion sensor of choice in oil and gas exploration surveys for many years and for good reason: they require no electrical power to operate, are lightweight, robust, and able to detect extremely small ground displacements. However, the seismic industry recently has developed considerable interest in microelectro mechanical systems (MEMS) accelerometers, which are similar to those used to sense accelerations for airbag deployment and missile guidance (among many other uses). The MEMS element is tied to an application specific integrated circuit (ASIC) that includes sensor signal conditioning, feedback control, and digitization blocks. The result is a custom-built unit for seismic applications that requires a power supply to operate.

Thermally adaptive response‐time compensation for LCDs

Abstract— This paper presents thermally adaptive driving (TAD) technology for response‐time compensation (RTC) of an LCD with an integrated sensor. The TAD system is comprised of an analog sensor, an analog sensor signal conditioning, and a digital feedback algorithm. The integrated thermal sensor provides accurate temperature measurement of the liquid‐crystal layer. The TAD controller has an eight‐step look‐up‐table (LUT) and compensates response time based on the panel temperature. The TAD system reduces response time by nearly 34% over the temperature range 0–60°C. This paper also presents a thermal sensor which has been integrated onto an LCD. The sensor uses metal (Mo/Al) film as a temperature detection layer, and its fabrication requires no manufacturing process changes. The sensor shows very good linearity, sensitivity, and reliability.

Switched Capacitor Signal Conditioning for Differential Capacitive Sensors

A novel switched capacitor signal-conditioning circuit for differential capacitive sensors is proposed. The main advantage of the proffered method lies in the fact that it accepts sensors possessing either linear or inverse characteristics and provides a linear output. Moreover, the output is dependent only on a pair of dc reference voltages and the transformation constant of the sensor. Hence, increased linearity and accuracy is easily achieved by employing precision dc reference voltages. Results from the tests on a prototype elucidate the practicality of the proposed method

P‐78: A Thermally Adaptive Response Time Compensation System for LCD Panels

AbstractThis paper presents thermally adaptive driving (TAD) technology for response time compensation (RTC) of an LCD with an integrated sensor. The TAD is comprised of analog sensor signal conditioning and a digital feedback algorithm. The integrated thermal sensor provides accurate temperature measurement of the liquid crystal layer. The TAD controller has an 8‐step look‐up‐table (LUT), and compensates response time based on the panel temperature. The TAD system reduces response time by nearly 50% over the temperature range 0 ° −; 60 °C.

Signal conditioning for GMR magnetic sensors: Applied to traffic speed monitoring GMR sensors

The Earth's magnetic field provides a uniform magnetic field over a wide area of several kilometers, among 30 and 60 μT depending on the location. Thus, cars, which have a high ferrous content mainly under car parts, provoke local disturbances around 1 μT over the constant Earth's magnetic field whether it is moving or still standing. Giant Magneto-Resistance (GMR) gradient sensors are able to convert this Earth's magnetic field variations into a voltage signature, due to the “Giant Magnetoresistive Effect”. Nevertheless, the output of the GMR sensors is too weak to operate with, and it must be amplified and filtered enough to be digitized and then processed. In this paper, we show the design and implementation of a practical conditioner circuit for GMR sensors and a simple speed calculation algorithm used in our embedded speed monitoring system for vehicles. The signal conditioner has been adjusted for car applications, where a high gain in a certain bandwidth is required due to the relatively large distance between the sensors on the pavement and the under car parts. Our conditioning circuit amplifies the sensor's output voltage by 36.360 in a bandwidth among 0.19 and 48.23 Hz. We present, compare and analyze two real car signals captured with our embedded system. With the small and cheap magnetic sensors and only a few additional components, our embedded speed monitoring system is suitable in automotive applications, where it would drastically reduce the cost of the expensive installation procedures of current car speed monitoring systems or even car detecting systems.

On-Chip Electrochemical Analysis System Using Nanoelectrodes and Bioelectronic CMOS Chip

An electrochemical microanalysis system for reversible redox species determination has been presented. This system consists of a nanoelectrochemical sensor and a complimentary metal-oxide-semiconductor (CMOS) chip for sensor signal interfacing and conditioning. The nanoelectrochemical sensor is an interdigitated array nanoelectrode fabricated using e-beam lithography and ultraviolet lithography. The CMOS chip is designed and fabricated to realize the electrochemical analysis method of sensing, which is a switch-based method. Using this switch-based method, the potential dynamics of the nanoelectrodes is recorded to evaluate the species concentration. Experimental results have shown that the detection limit of this microanalysis system on reversible redox species is in the range of 1-10 nM

A hardware development for optical tomography system using switch mode fan beam projection

This research used 16 pairs of optical sensors. The working principle is based on the switch and measure principle in electrical capacitance tomography (ECT), and fan beam shape projection from light emitters. The fast setting time of optical sensors and wide coverage of optical beam become the is implemented in a tomography system. In general, the system can be divided to three subsystems; they are projection, sensor signal conditioning and data acquisition. In the projection subsystem, a 4.8 kHz clock has been used to drive the LEDs, as a result, 300 complete projections obtained in a second. In the signal conditioning subsystem, a current to voltage converter has been used with each photodiode output, the signals are filtered and amplified before interfacing with the data acquisition system. In the data acquisition system, a computer based data acquisition system has been utilized. The modulated clocks from the projection sub-system are used to control the operation of data acquisition. This paper will discuss the detail of hardware development and shows the result obtained from the designed hardware system.

A micro-fluxgate sensor based on the Matteucci effect of amorphous magnetic fibers

Abstract The design, construction and performance of a novel micro-fluxgate sensor is presented in this work. The sensor is based on the large Matteucci effect that is observed in amorphous fibers of typical stoicheiometry Fe77.5Si7.5B15 after proper annealing. The sensor requires a single planar coil to function, which was constructed with conventional printed-circuit techniques along with the sensor signal conditioning circuitry. A new signal extraction technique was applied that is superior to the conventional second-order-harmonic concept, as far as sensitivity and signal-to-noise ratio are concerned. A conventional fiber, with diameter 125 μm and a glass-covered fiber, with core diameter 20 μm and glass-cover thickness 20 μm, were used as magnetic cores in the fluxgate sensor. The amorphous fibers were mounted, subsequently, above a planar coil by soldering each two ends without any further mechanical treatment, like bending or twisting. Current annealing was performed before mounting, for both magnetic core types in order to optimize the inductive response of the fibers. The sensor sensitivity, before amplification, was measured to be 74000 V/T. The low magnetic noise observed allows for a relatively high overall precision, which in the case of glass-covered fiber has been verified to be 60 nT; this figure may easily improve by known signal conditioning techniques. The overall sensor head dimensions are 60 mm ×30 mm. Further scaling down may be achieved by means of advanced lithographic techniques in the case of glass-covered amorphous fibers only, which exhibit significant Matteucci effect in lengths down to 5 mm.

Microfabricated Shear Stress Sensors, Part 1: Design and Fabrication

The design and fabrication of shear stress sensors based on the floating-element method and polysilicon-surface-micromachining technology is reported. Three designs have been developed for microfabrication, two including monolithic integration of mechanical sensor elements with on-chip circuitry. The first design is four-mask standard polysilicon-surface-micromachining process to develop passive floating-element sensors with optically determined deflection sensitivity. The second-generation devices are fabricated in a six-mask modified N-channel metal-oxide-semiconductor process, where sensor elements and signal conditioning circuitry have been integrated on the sensor die for amplified voltage output. The third design modifies the commercially available micromachined by replacing the accelerometer element with a shear-stress-sensitive floating element, enabling active sensing for linear response and self-test features