Readout System For Sensors Research Articles

Capacitive Readout System for Micro Sensors and Actuators With Automatic Parasitic Cancellation

In this article, a capacitive readout system with automatic parasitic capacitance cancellation function is designed and implemented. The readout system is implemented with discrete components on a board level. The parasitic cancellation is realized by matching a digital programmable capacitor to the parasitic capacitance using a PI controller. The function of the readout system is verified by using standard ceramic capacitors and a MEMS micromirror device. Capacitance measurements up to 35 pF for ceramic capacitors are performed, the maximum error between the measurement results of the circuit and an LCR meter is 0.07 pF. For MEMS micromirror, the circuit cancels the parasitic capacitance of 32.63 pF and realizes a measurement error within 0.06 pF. The proposed system can be used as a proof-of-concept platform demonstrating the feasibility of the generic parasitic cancellation method for MEMS sensors and actuators.

Readout Circuits for Capacitive Sensors.

The development of microelectromechanical system (MEMS) processes enables the integration of capacitive sensors into silicon integrated circuits. These sensors have been gaining considerable attention as a solution for mobile and internet of things (IoT) devices because of their low power consumption. In this study, we introduce the operating principle of representative capacitive sensors and discuss the major technical challenges, solutions, and future tasks for a capacitive readout system. The signal-to-noise ratio (SNR) is the most important performance parameter for a sensor system that measures changes in physical quantities; in addition, power consumption is another important factor because of the characteristics of mobile and IoT devices. Signal power degradation and noise, which degrade the SNR in the sensor readout system, are analyzed; circuit design approaches for degradation prevention are discussed. Further, we discuss the previous efforts and existing studies that focus on low power consumption. We present detailed circuit techniques and illustrate their effectiveness in suppressing signal power degradation and achieving lower noise levels via application to a design example of an actual MEMS microphone readout system.

A Soft-Error-Tolerant SAR ADC with Dual-Capacitor Sample-and-Hold Control for Sensor Systems.

For a reliable and stable sensor system, it is essential to precisely measure various sensor signals, such as electromagnetic field, pressure, and temperature. The measured analog signal is converted into digital bits through the sensor readout system. However, in extreme radiation environments, such as in space, during flights, and in nuclear fusion reactors, the performance of the analog-to-digital converter (ADC) constituting the sensor readout system can be degraded due to soft errors caused by radiation effects, leading to system malfunction. This paper proposes a soft-error-tolerant successive-approximation-register (SAR) ADC using dual-capacitor sample-and-hold (S/H) control, which has robust characteristics against total ionizing dose (TID) and single event effects (SEE). The proposed ADC was fabricated using 65-nm CMOS process, and its soft-error-tolerant performance was measured in radiation environments. Additionally, the proposed circuit techniques were verified by utilizing a radiation simulator CAD tool.

Temperature and Pressure Composite Measurement System Based on Wireless Passive LC Sensor

In this article, we proposed a measurement system that can simultaneously measure temperature and pressure. By analyzing several existing measurement methods of the sensor, we determined that the resonance frequency and $S_{11}$ (reflection coefficient) amplitude of the sensor readout system should be measured when the resonance frequency of the sensor up to a hundred megahertz or even gigahertz and when the sensor works in ultrahigh temperature environment. In addition, we designed a simple and accurate sensor readout circuit and an LC temperature–pressure sensor. By analyzing the resonance frequency and the amplitude of $S_{11}$ , temperature and pressure were measured simultaneously with a single LC circuit. Since the analysis of the whole nonlinear system of sensors is complex, we divide the entire nonlinear system into several linear systems superposition. By analyzing the interference between temperature and pressure, we further optimized the measurement method. The relative errors of the temperature measurements in the range of 25 °C–300 °C and 300 °C–1000 °C were only 2.89% and 1.25%, respectively. From 25 °C to 300 °C and 300 °C to 1000 °C, the average relative errors of pressure measurement were only 4.07% and 4.74%, respectively. Besides, the proposed method can also be widely used in the measurement of LC multiparameter sensors.

A Radiation-Hardened SAR ADC with Delay-Based Dual Feedback Flip-Flops for Sensor Readout Systems.

For stable and effective control of the sensor system, analog sensor signals such as temperature, pressure, and electromagnetic fields should be accurately measured and converted to digital bits. However, radiation environments, such as space, flight, nuclear power plants, and nuclear fusion reactors, as well as high-reliability applications, such as automotive semiconductor systems, suffer from radiation effects that degrade the performance of the sensor readout system including analog-to-digital converters (ADCs) and cause system malfunctions. This paper investigates an optimal ADC structure in radiation environments and proposes a successive- approximation-register (SAR) ADC using delay-based double feedback flip-flops to enhance the system tolerance against radiation effects, including total ionizing dose (TID) and single event effects (SEE). The proposed flip-flop was fabricated using 130 nm complementary metal–oxide–semiconductor (CMOS) silicon-on-insulator (SOI) process, and its radiation tolerance was measured in actual radiation test facilities. Also, the proposed radiation-hardened SAR ADC with delay-based dual feedback flip-flops was designed and verified by utilizing compact transistor models, which reflect radiation effects to CMOS parameters, and radiation simulator computer aided design (CAD) tools.

Development of low-cost hybrid multi-walled carbon nanotube-based ammonia gas-sensing strips with an integrated sensor read-out system for clinical breath analyzer applications

This work demonstrates the development of Ag@polyaniline/multi-walled carbon nanotube nanocomposite-based sensor strips and a suitable integrated electronic read-out system for the measurement of trace-level concentrations of ammonia (NH3). The sensor is optimized under various operating conditions and the resulting sensor exhibited an enhanced response (32% for 2 ppm) with excellent selectivity. Stable performance was observed towards NH3 in the presence of high concentrations of CO2 (>40 000 ppm), simulated and real breath samples. A suitable electronic sensor read-out system has also been designed and developed based on multi-scale resistance-to-voltage conversion architecture, processed by a 32-bit microcontroller which is operatable over a wide range of sensor resistance (1 kΩ to 200 MΩ). As a proof of concept, integration of gas-sensing strips with the electronic read-out system was tested with various levels of NH3 (<2 ppm as normal, >2 ppm as critical and 2 ppm as threshold), which is important for clinical breath analyzer applications. The developed prototype device can be readily incorporated into a portable, low-cost and non-invasive point-of-care breath NH3 detection unit for portable pre-diagnostic breath analyzer applications.

A Reconfigurable, Pulse-shaping Potentiometric Readout System for Bio-Sensing Transistors.

This paper presents a new multi-modality readout system for potentiometric electrochemical sensors. The design adopts a pulse modulation at the gate and drain of the Bio-FET sensors to reduce the effects of charge accumulation between the surface of the electrodes and the ion analytes. The adjustable duration and amplitude of stimuli signals provide flexibility for different biosensing applications and a wide range of detectable concentration. Also, an oscillator-based architecture is proposed for digitization and integration. The counting time can be adjusted to enhance the resolution of the readout system. The proposed potentiometric sensing system was tested with 0.1-10 mM Potassium Ferricyanide (K3[Fe(CN)6]), and the results are interpreted in the micro-LCD on the board. The design offers the opportunity for a handheld medical device with fast and real-time monitoring of biomarkers and ion analytes.

Characterization of noise and efficiency of the Pixirad-1/Pixie-III CdTe X-ray imaging detector

Thanks to their high detection efficiency and low intrinsic noise, direct conversion X-ray Photon Counting Detectors (XPCDs) are particularly suitable for low dose imaging applications such as mammography. The photon counting technology can implement also two or more acquisition thresholds to perform single-shot spectral imaging with one polychromatic source. However, XPCDs with thick high Z crystal sensor and small pixel size are affected by the charge sharing effect. This issue can induce multiple counts from a single interaction reducing both spectral and spatial resolutions. In a pure counting mode, multiple counts from charge sharing can be partially or totally removed by increasing the acquisition threshold at the cost of a loss of efficiency. Thus, the performances of XPCDs can be threshold-dependent. New generation XPCDs implement solutions to cope with charge sharing issue. If the charge sharing is properly corrected, no multiple counts are recorded and the performances (detection efficiency, spectral and spatial resolutions) of the acquisition system are expected to be independent from the acquisition threshold. This work presents a study of a Pixirad-1 detection system based on a CdTe Schottky sensor and PIXIE-III readout system. This chip can be configured in three different operation modes, two of which implement solutions to remove multiple counts. Using monochromatic radiation, the performances of these different operation modes have been compared trough a measure of the integral spectra and the Signal to Noise Ratio (SNR) as function of the acquisition threshold.

Utilization of data classification in the realization of a surface Plasmon resonance readout system using an FPGA controlled RGB LED light source

This paper presents the realization of a surface plasmon resonance (SPR) sensor readout system using a tricolor red, green, and blue light emitting diode light source. Time domain intensity modulation of each color channel is applied to interrogate three bands of interest in the SPR spectrum using a single photodiode detector. A low computing resource classification approach is used through the combination of k-nearest neighbor (kNN) and adapted clustering using representative. An optimized number of representatives is chosen in the validation process to reduce the required amount of data for the kNN classification. This scheme was used to classify the concentrations of different glucose solutions. The sensor readout system hardware is based on the use of a field programmable gate array and the glucose solution classification is developed and undertaken on a personal computer using the Python open source programming language.

All-printed highly sensitive 2D MoS2 based multi-reagent immunosensor for smartphone based point-of-care diagnosis

Immunosensors are used to detect the presence of certain bio-reagents mostly targeted at the diagnosis of a condition or a disease. Here, a general purpose electrical immunosensor has been fabricated for the quantitative detection of multiple bio-reagents through the formation of an antibody-antigen pair. The sensors were fabricated using all printing approaches. 2D transition metal dichalcogenide (TMDC) MoS2 thin film was deposited using Electrohydrodynamic atomization (EHDA) on top of an interdigitated transducer (IDT) electrode fabricated by reverse offset printing. The sensors were then treated with three different types of antibodies that were immobilized by physisorption into the highly porous multi-layered structure of MoS2 active layer. BSA was used as blocking agent to prevent non-specific absorption (NSA). The sensors were then employed for the targeted detection of the specific antigens including prostate specific antigen (PSA), mouse immunoglobulin-G (IgG), and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). IgG was then selected to test the sensors for point of care (POC) diagnosis through a specially designed electronic readout system for sensors and interfacing it with a smartphone using Bluetooth connection. The sensors showed promising performance in terms of stability, specificity, repeatability, sensitivity, limit of detection (LoD), and range of detection (RoD).

An Inkjet-Printed Non-Enzymatic Hydrogen Peroxide Sensor on Paper

This paper reports a novel disposable non-enzymatic hydrogen peroxide sensor fabricated using an inkjet printing method on paper. An electrochemical cell based on carbon nanotubes was patterned and printed on a paper substrate. Silver nanoparticles have been used as the catalyst for electrochemical reduction of H2O2. Moreover, a handheld multichannel potentiostat was developed in order to on-site determination of hydrogen peroxide. The device was characterized by performing simultaneous cyclic voltammetry measurements utilizing separate working electrodes at various scan rates. Using the presented system, we successfully measured the hydrogen peroxide concentration in an alkaline solution with the linear range of 1 μM–700 μM. Incorporating the paper-based enzyme-free sensor and portable readout system will result in accurate, reliable, cost effective, and on-site measurement of hydrogen peroxide in concentration as low as 1 μM.

CMS Pixel Detector design for HL-LHC

The LHC machine is planning an upgrade program which will smoothly bring the luminosity to about 7.5×1034cm−2s−1 in 2028, to possibly reach an integrated luminosity of 3000 fb−1 by the end of 2037. This High Luminosity scenario, HL-LHC, will present new challenges in higher data rates and increased radiation. In order to maintain its physics reach the CMS collaboration has undertaken a preparation program of the detector known as Phase-2 upgrade. The CMS Phase-2 Pixel upgrade will require a high bandwidth readout system and high radiation tolerance for sensors and on-detector ASICs. Several technologies for the upgrade sensors are being studied. Serial powering schemes are under consideration to accommodate significant constraints on the system. These prospective designs, as well as new layout geometries that include very forward pixel discs, will be presented together with performance estimation.

A Multi(bio)sensor Acquisition System With Integrated Processor, Power Management, $8 \times 8$ LED Drivers, and Simultaneously Synchronized ECG, BIO-Z, GSR, and Two PPG Readouts

A battery-powered multisensor acquisition system with five dedicated channels [electrocardiograph (50 μW), bioimpedance (46 μW), galvanic skin response (15 μW), and 2× photoplethysmogram (134 μW)] is presented. It includes an ARM Cortex M0, analog and digital filters, timestamp converter and sample rate converter (SRC), and generic interfaces to support additional sensor modalities. The timestamp module makes precise synchronization between the data streams possible. The SRC module makes the sample rates of data from the internal and external sensor readouts compatible with each other, and is up to a factor 35 more energy efficient compared with a software solution. These modules enable performing accurate and reliable (correlation) techniques. The power management includes two buck converters, an LDO, and eight LED drivers, supporting up to 64 LEDs in an 8 × 8 matrix organization. It makes this system the most complete and versatile sensor readout system with state-of-the-art performance (1073 μW with all channels enabled).

Development of a Standardised Readout System for Active Pixel Sensors in HV/HR-CMOS Technologies for ATLAS Inner Detector Upgrades

The LHC Phase-II Upgrade results in new challenges for tracking detectors for example in terms of cost effectiveness, resolution and radiation hardness. Active Pixel Sensors in HV/HR-CMOS technologies show promising results coping with these challenges. In order to demonstrate the feasibility of hybrid modules with active CMOS sensors and readout chips for the future ATLAS Inner Tracker, ATLAS R&D activities have started. After introducing the basic concepts and the demonstrator program, the development of an ATLAS compatible readout system will be presented as well as tuning procedures and measurements with demonstrator modules to test the readout system.

A Distance Compensated Approach Used in Wireless Passive Pressure Sensor Readout System for High Temperature Application

This paper proposed a distance compensated measurement system for a wireless passive sensor based on the high temperature cofired ceramics (HTCC) applied to high temperature environment. The sensor model is provided and fabricated. Also, a telemetric measurement system consists of a readout instrumentation and a heat insulation unit is described due to the thickness of heat insulation material between the sensor and readout unit’s inductance coils in high temperature testing environment. Consideration of the leakage inductance and parasitic parameters which depend on the coupling distance is equivalent to the thickness of heat insulation material, and a distance compensated method is presented. The compensation is based on the mathematical feature of the testing results from readout unit which show us information about the relation between the extracted resonant frequencies. This method can be used simply and reliably in the other telemetric mutual inductance coupling readout system as a viable solution to compensate the coupling distance related error when inductive coupling is varied. It has been experimentally tested, and the results are in good agreement with those measured by a reference impedance analysis instrument. Theoretical explanations, experimental results, and discussion are reported.

A Continuous-Time Ripple Reduction Technique for Spinning-Current Hall Sensors

This paper presents a new ripple-reduction technique for spinning-current Hall sensors, which obviates the need for low-pass filtering to suppress the ripple caused by up-modulated sensor offset. A continuous-time ripple-free output is achieved by the use of three ripple reduction loops (RRLs), which continuously sense the offset ripple and then use this information to drive a feedback loop that cancels sensor offset before amplification. Since no low-pass filter is involved, the bandwidth of the resulting system can be much higher than the spinning frequency. Moreover, since the front-end no longer has to process sensor offset, the requirements on its dynamic range can be significantly relaxed. A prototype system consisting of a Hall sensor readout system realized in a 0.18 μm CMOS process was combined with three off-chip RRLs realized with off-chip electronics. At a spinning frequency of 1 kHz, the RRLs reduce the offset ripple by more than 40 dB to about 10 μT, while also achieving low offset (25 μT) and wide bandwidth (over 100 kHz).

A novel readout system for wireless passive pressure sensors

This paper presents a novel readout system for wireless passive pressure sensors based on the inductively coupled inductor and cavity (LC) resonant circuits. The proposed system consists of a reader antenna inductively coupled to the sensor circuit, a readout circuit, and a personal computer (PC) post processing unit. The readout circuit generates a voltage signal representing the sensor’s capacitance. The frequency of the reader antenna driving signal is a constant, which is equal to the sensor’s resonant frequency at zero pressure. Based on mechanical and electrical modeling, the pressure sensor design based on the high temperature co-fired ceramic (HTCC) technology is conducted and discussed. The functionality and accuracy of the readout system are tested with a voltage-capacitance measurement system and demonstrated in a realistic pressure measurement environment, so that the overall performance and the feasibility of the readout system are proved.

A readout system for passive pressure sensors

This paper presents a readout system for the passive pressure sensors which consist of a pressure-sensitive capacitor and an inductance coil to form an LC circuit. The LC circuit transforms the pressure variation into the LC resonant frequency shift. The proposed system is composed of a reader antenna inductively coupled to the sensor inductor, a measurement circuit, and a PC post-processing unit. The measurement circuit generates a DC output voltage related to the sensor's resonant frequency and converts the output voltage into digital form. The PC post-processing unit processes the digital data and calculates the sensor's resonant frequency. To test the performance of the readout system, a sensor is designed and fabricated based on low temperature co-fired ceramic (LTCC), and a series of testing experiments is carried out. The experimental results show good agreement with the impedance analyzer's results, their error is less than 2.5%, and the measured values are almost insensitive to the variation of readout distance. It proves that the proposed system is effective practically.

Robustness analysis of an intensity modulated fiber-optic position sensor with an image sensor readout system

An intensity modulated fiber-optic position sensor, based on a fiber-to-bundle coupling and a readout system using a CMOS image camera together with fast routines for position extraction and calibration, is presented and analyzed. The proposed system eliminates alignment issues otherwise associated with coupling-based fiber-optic sensors, still keeping the sensing point free from detector electronics. In this study the robustness of the system is characterized through simulations of the system performance, and the outcome is compared with experimental results. It is shown that knowledge of the shape of the coupled power distribution is the single most important factor for high performance of the system. Further it is experimentally shown that the position extraction error can be improved down to the theoretical limit by employing a modulation function model well fitted to the real coupled power distribution.

Note: A versatile, stable, high-resolution readout system for RTD and thermistor sensors

A readout system for resistance temperature detectors and thermistors is described featuring temperature resolution better than 1 mK and capability to fit sensors having different resistance or requiring different excitation current. For instance, with a sensor equivalent to an ideal 100 Ω Pt, an excitation current of 0.7 mA, and reading @ 1Hz, the system resolution corresponds to 0.38 mK and its temperature coefficient (TC) to 0.26 mK/K. The system, however, can control its own temperature accurately enough to make its TC negligible. When thermostated, the overall stability of the system was better than 10 ppm for 230 h.