Resistive Sensor Array Research Articles

Scanning Approaches of 2-D Resistive Sensor Arrays: A Review

With scanning approaches of low complexity, the 2-D resistive sensor arrays (RSAs) are used to extract the distribution of sensed variable values (e.g., physical pressure) over the sensing area. This review surveys the scanning approaches of the 2-D RSAs, their evaluation methods, and their applications. The principle of the 2-D RSA with the scanning approach is introduced first. Then, different scanning approaches of RSAs are illustrated. The scanning approaches of RSAs are mainly categorized into the inserting diode method, the inserting transistor method, the passive integrator method, the resistance matrix approach, the incidence matrix approach, the voltage feedback method, the zero potential method, and so on. Next, various evaluation methods of the scanning approaches are presented. The scanning approach’s evaluation methods are categorized into testing of the actual system, analyzing with circuit simulation software, and analyzing with test model. Followed, typical applications of the 2-D RSAs with the scanning approaches and their special requirements are analyzed. Finally, the characteristics of various typical scanning approaches and their development tendency are discussed and investigated in detail.

An Improved Zero Potential Circuit for Readout of a Two-Dimensional Resistive Sensor Array.

With one operational amplifier (op-amp) in negative feedback, the traditional zero potential circuit could access one element in the two-dimensional (2-D) resistive sensor array with the shared row-column fashion but it suffered from the crosstalk problem for the non-scanned elements’ bypass currents, which were injected into array’s non-scanned electrodes from zero potential. Firstly, for suppressing the crosstalk problem, we designed a novel improved zero potential circuit with one more op-amp in negative feedback to sample the total bypass current and calculate the precision resistance of the element being tested (EBT) with it. The improved setting non-scanned-electrode zero potential circuit (S-NSE-ZPC) was given as an example for analyzing and verifying the performance of the improved zero potential circuit. Secondly, in the S-NSE-ZPC and the improved S-NSE-ZPC, the effects of different parameters of the resistive sensor arrays and their readout circuits on the EBT’s measurement accuracy were simulated with the NI Multisim 12. Thirdly, part features of the improved circuit were verified with the experiments of a prototype circuit. Followed, the results were discussed and the conclusions were given. The experiment results show that the improved circuit, though it requires one more op-amp, one more resistor and one more sampling channel, can access the EBT in the 2-D resistive sensor array more accurately.

PDMS/MWCNT-based tactile sensor array with coplanar electrodes for crosstalk suppression.

The severe crosstalk effect is widely present in tactile sensor arrays with a sandwich structure. Here we present a novel design for a resistive tactile sensor array with a coplanar electrode layer and isolated sensing elements, which were made from polydimethylsiloxane (PDMS) doped with multiwalled carbon nanotubes (MWCNTs) for crosstalk suppression. To optimize its properties, both mechanical and electrical properties of PDMS/MWCNT-sensing materials with different PDMS/MWCNT ratios were investigated. The experimental results demonstrate that a 4 wt% of MWCNTs to PDMS is optimal for the sensing materials. In addition, the pressure-sensitive layer consists of three microstructured layers (two aspectant PDMS/MWCNT-based films and one top PDMS-based film) that are bonded together. Because of this three-layer microstructure design, our proposed tactile sensor array shows sensitivity up to −1.10 kPa−1, a response time of 29 ms and reliability in detecting tiny pressures.

Strain Sensing Sheets for Structural Health Monitoring Based on Large-Area Electronics and Integrated Circuits

Accurate and reliable damage characterization (i.e., damage detection, localization, and evaluation of extent) in civil structures and infrastructure is an important objective of structural health monitoring (SHM). Highly accurate and reliable characterization of damage at early stages requires continuous or quasi-continuous direct sensing of the critical parameters. Direct sensing requires deploying dense arrays of sensors, to enhance the probability that damage will result in signals that can be directly acquired by the sensors. However, coverage by dense arrays of sensors over the large areas that are of relevance represents an enormous challenge for current technologies. Large area electronics (LAE) is an emerging technology that can enable the formation of dense sensor arrays spanning large areas (several square meters) on flexible substrates. This paper explores the requirements and technology for a sensing sheet for SHM based on LAE and crystalline silicon CMOS integrated circuits (ICs). The sensing sheet contains a dense array of thin-film full-bridge resistive strain sensors, along with the electronics for strain readout, full-system self-powering, and communication. Research on several stages is presented for translating the sensing sheet to practical SHM applications. This includes experimental characterization of an individual sensor’s response when exposed to cracks in concrete and steel; theoretical and experimental performance evaluation of various geometrical parameters of the sensing sheet; and development of the electronics necessary for sensor readout, power management, and sensor-data communication. The concept of direct sensing has been experimentally validated, and the potential of a sensing sheet to provide direct sensing and successful damage characterization has been evaluated in the laboratory setting. A prototype of the sensing sheet has also been successfully developed and independently characterized in the laboratory, meeting the required specifications. Thus, a sensing sheet for SHM applications shows promise both in terms of practicality and effectiveness.

A Novel Two-Wire Fast Readout Approach for Suppressing Cable Crosstalk in a Tactile Resistive Sensor Array.

For suppressing the crosstalk problem due to wire resistances and contacted resistances of the long flexible cables in tactile sensing systems, we present a novel two-wire fast readout approach for the two-dimensional resistive sensor array in shared row-column fashion. In the approach, two wires are used for every driving electrode and every sampling electrode in the resistive sensor array. The approach with a high readout rate, though it requires a large number of wires and many sampling channels, solves the cable crosstalk problem. We also verified the approach’s performance with Multisim simulations and actual experiments.

Approximate Model of Zero Potential Circuits for the 2-D Networked Resistive Sensor Array

To fast evaluate the features of the zero potential circuits (ZPCs) for the 2-D networked resistive sensor arrays, such as the setting non-scanned-electrode ZPC, the setting non-scanned-sampling-electrode ZPC, and the setting non-scanned-driving-electrode ZPC, we first proposed the approximate models of the ZPCs with one op-amp. By analyzing the approximate model, we then gave a mathematical expression of the effective equivalent resistor of the element being tested in the ZPCs with one op-amp. Finally, we evaluated the approximate model of the ZPCs with one op-amp by simulation experiments. The results show that the proposed approximate model of the ZPCs with one op-amp is applicable to fast analyze the performance of the resistive sensor array parameters, including array size and the resistance range of the sensitive elements, and the ZPCs’ parameters, including the multiplexers’ switch resistors, the gain of the zero potential op-amp, and the resistance value of the sampling resistor.

Cable Crosstalk Suppression with Two-Wire Voltage Feedback Method for Resistive Sensor Array.

Using a long, flexible test cable connected with a one-wire voltage feedback circuit, a resistive tactile sensor in a shared row-column fashion exhibited flexibility in robotic operations but suffered from crosstalk caused by the connected cable due to its wire resistances and its contacted resistances. Firstly, we designed a new non-scanned driving-electrode (VF-NSDE) circuit using two wires for every row line and every column line to reduce the crosstalk caused by the connected cables in the circuit. Then, an equivalent resistance expression of the element being tested (EBT) for the two-wire VF-NSDE circuit was analytically derived. Following this, the one-wire VF-NSDE circuit and the two-wire VF-NSDE circuit were evaluated by simulation experiments. Finally, positive features of the proposed method were verified with the experiments of a two-wire VF-NSDE prototype circuit. The experiment results show that the two-wire VF-NSDE circuit can greatly reduce the crosstalk error caused by the cables in the 2-D networked resistive sensor array.

Accuracy and Resolution Analysis of a Direct Resistive Sensor Array to FPGA Interface.

Resistive sensor arrays are formed by a large number of individual sensors which are distributed in different ways. This paper proposes a direct connection between an FPGA and a resistive array distributed in M rows and N columns, without the need of analog-to-digital converters to obtain resistance values in the sensor and where the conditioning circuit is reduced to the use of a capacitor in each of the columns of the matrix. The circuit allows parallel measurements of the N resistors which form each of the rows of the array, eliminating the resistive crosstalk which is typical of these circuits. This is achieved by an addressing technique which does not require external elements to the FPGA. Although the typical resistive crosstalk between resistors which are measured simultaneously is eliminated, other elements that have an impact on the measurement of discharge times appear in the proposed architecture and, therefore, affect the uncertainty in resistance value measurements; these elements need to be studied. Finally, the performance of different calibration techniques is assessed experimentally on a discrete resistor array, obtaining for a new model of calibration, a maximum relative error of 0.066% in a range of resistor values which correspond to a tactile sensor.

High-Accuracy, Compact Scanning Method and Circuit for Resistive Sensor Arrays.

The zero-potential scanning circuit is widely used as read-out circuit for resistive sensor arrays because it removes a well known problem: crosstalk current. The zero-potential scanning circuit can be divided into two groups based on type of row drivers. One type is a row driver using digital buffers. It can be easily implemented because of its simple structure, but we found that it can cause a large read-out error which originates from on-resistance of the digital buffers used in the row driver. The other type is a row driver composed of operational amplifiers. It, very accurately, reads the sensor resistance, but it uses a large number of operational amplifiers to drive rows of the sensor array; therefore, it severely increases the power consumption, cost, and system complexity. To resolve the inaccuracy or high complexity problems founded in those previous circuits, we propose a new row driver which uses only one operational amplifier to drive all rows of a sensor array with high accuracy. The measurement results with the proposed circuit to drive a 4 × 4 resistor array show that the maximum error is only 0.1% which is remarkably reduced from 30.7% of the previous counterpart.

Improved Circuits with Capacitive Feedback for Readout Resistive Sensor Arrays.

One of the most suitable ways of distributing a resistive sensor array for reading is an array with M rows and N columns. This allows reduced wiring and a certain degree of parallelism in the implementation, although it also introduces crosstalk effects. Several types of circuits can carry out the analogue-digital conversion of this type of sensors. This article focuses on the use of operational amplifiers with capacitive feedback and FPGAs for this task. Specifically, modifications of a previously reported circuit are proposed to reduce the errors due to the non-idealities of the amplifiers and the I/O drivers of the FPGA. Moreover, calibration algorithms are derived from the analysis of the proposed circuitry to reduce the crosstalk error and improve the accuracy. Finally, the performances of the proposals is evaluated experimentally on an array of resistors and for different ranges.

Cable Crosstalk Suppression in Resistive Sensor Array with 2-Wire S-NSDE-EP Method

With long flexible cables connected to the 1-wire setting non-scanned-driving-electrode equipotential (S-NSDE-EP) circuit, the resistive sensor array modules got flexibility in robotic operations but suffered from the crosstalk problem caused by wire resistances and contacted resistances of the cables. Firstly, we designed a new S-NSDE-EP circuit using two wires for every driving-electrode and every sampling-electrode to reduce the crosstalk caused by the connected cables in the 2D networked resistive sensor array. Then, an equivalent resistance expression of the element being tested (EBT) for this circuit was analytically derived. Then, the 1-wire S-NSDE-EP circuit and the 2-wire S-NSDE-EP circuit were evaluated by simulations. The simulation results show that the 2-wire S-NSDE-EP circuit, though it requires a large number of wires, can greatly reduce the crosstalk error caused by wire resistances and contacted resistances of the cables in the 2D networked resistive sensor array.

Fluid dynamic analysis and experimental study of a temperature sensor array used in meteorological observation

Until now, the air temperature sensors inside thermometer screens and radiation shields are affected by solar radiation, which causes the measuring result to become greater than the actual temperature. The temperature rise can reach 0.8 K or even higher. In this paper, a temperature sensor array design is established for obtaining high precision measurement results. The temperature sensor array consists of an array of radiation shields which features a tube-shape, a platinum resistance sensor array, an aluminum plate with a silver mirror surface and a temperature measurement module that includes a high accuracy thermometer circuit. There is always at least one radiation shield that supplies relatively good ventilation under any airflow direction. A computational fluid dynamic method is implemented to analyze and calculate the temperature rise induced by radiation under various environmental conditions. A correction equation of the temperature rise is obtained by surface fitting using a genetic algorithm. The measurement accuracy can be further improved by this correction equation. In order to verify the performance of the sensor array, a forced ventilation temperature measurement platform is constructed, which consists of a platinum resistance sensor, an L-shaped radiation shield and an air pump. The airflow rate inside the radiation shield can be up to 20~m/s, and the L-shaped radiation shield can horizontally rotate under the control of a software to minimize the error caused by the heated radiation shield. The temperature sensor array, a temperature sensor with traditional radiation shield, and the forced ventilation temperature measurement platform are characterized in the same environment. To experimentally verify the computational fluid dynamic method and the genetic algorithm, a number of contrast tests are performed. The average temperature rise of sensors equipped with the traditional radiation shields is 0.409 K. In contrast, the temperature rise of the sensor array is as low as 0.027K. This temperature sensor array allows the error caused by solar radiation to be reduced by a percentage of approximately 93%. The temperature rise of temperature sensor array, caused by the angular variation of airflow direction is on the order of several mK. When the solar radiation intensity and the airflow rate are 1000W/m2 and 0.1m/s, respectively, the temperature rise is 0.097 K. The temperature rise is 0.05K, when the airflow rate is greater than 0.4 m/s. The temperature rise can be reduced to 0.01 K, when the airflow rate is greater than 2 m/s. The average offset and root mean square error between the correction equation and experimental results are 0.0174 K and 0.0215 K, respectively, which demonstrates the accuracy of the computational fluid dynamic method and genetic algorithm proposed in this research. The temperature measurement accuracy has the potential to be further improved by utilizing the computational fluid dynamics method and the genetic algorithm.

Design and Crosstalk Error Analysis of the Circuit for the 2-D Networked Resistive Sensor Array

By sharing rows and columns, the 2-D networked resistive sensor arrays simplified the interconnect complexity but suffered from the crosstalk problem among its elements. The crosstalk was mainly affected by the multiplexers' resistor, adjacent column elements, adjacent row elements, and array size. First, we designed an improved isolated drive feedback circuit (IIDFC) using one operational amplifier to reduce the crosstalk caused by the adjacent column elements in the 2-D networked resistive sensor array. Then, a mathematical equivalent resistance expression of the element being tested (EBT) for this circuit was analytically derived. Then, the IIDFC and its equivalent resistance expression of the EBT were evaluated by the simulations. The simulation results show that the IIDFC can greatly reduce the crosstalk error caused by the adjacent column elements in the 2-D networked resistive sensor array with the row-column fashion and its resistance expression of the EBT can be used as a general formula to evaluate the performance of the IIDFC.

A New Approach for Readout of Resistive Sensor Arrays for Wearable Electronic Applications

Resistive sensor arrays have been increasingly adopted in wearable electronic applications, which require low-complexity and low-energy circuits. However, current readout strategies for resistive sensor arrays require additional electrical components, such as transistors, diodes, multiplexers, op-amps, switches, current sources, and A/D converters, leading to a considerable increase in circuit complexity, power consumption, system instability, and crosstalk error. To address the problem, this paper proposes a new approach, which determines sensor resistance values by establishing and solving resistance matrix equations of sensor arrays. Unlike conventional approaches, it allows crosstalk currents in arrays to avoid additional components that are originally used for eliminating crosstalk currents and minimizing crosstalk error. Meanwhile, it takes advantage of on-chip resources of wearable platforms, thereby reducing redundant chips. It was implemented on a prototype of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10\times 10$ </tex-math></inline-formula> textile resistive sensor array, which was taken in a sensing cushion for sitting pressure monitoring of chair bound people. Experimental results on this array platform showed the new approach achieved a satisfactory accuracy (0.61% ± 0.41%), as well as a low crosstalk error (2.77% ± 0.61%). The fabricated sensing cushion also exhibited a relatively low pressure measurement error (6.30% ± 0.75%). Compared with other approaches, the proposed approach demonstrated the lowest circuit complexity on a microcontroller based wearable platform, and a sufficient sensor capacity. It is ideal for a wide range of applications like wearable or implantable sensing, presenting a reference for the design of low-complexity and low-crosstalk error wearable systems based on resistive sensor arrays.

General Voltage Feedback Circuit Model in the Two-Dimensional Networked Resistive Sensor Array

To analyze the feature of the two-dimensional networked resistive sensor array, we firstly proposed a general model of voltage feedback circuits (VFCs) such as the voltage feedback non-scanned-electrode circuit, the voltage feedback non-scanned-sampling-electrode circuit, and the voltage feedback non-scanned-sampling-electrode circuit. By analyzing the general model, we then gave a general mathematical expression of the effective equivalent resistor of the element being tested in VFCs. Finally, we evaluated the features of VFCs with simulation and test experiment. The results show that the expression is applicable to analyze the VFCs’ performance of parameters such as the multiplexers’ switch resistors, the nonscanned elements, and array size.

Using Bayesian Inference Framework towards Identifying Gas Species and Concentration from High Temperature Resistive Sensor Array Data

High temperature gas sensors have been highly demanded for combustion process optimization and toxic emissions control, which usually suffer from poor selectivity. In order to solve this selectivity issue and identify unknown reducing gas species (CO, CH4, and CH8) and concentrations, a high temperature resistive sensor array data set was built in this study based on 5 reported sensors. As each sensor showed specific responses towards different types of reducing gas with certain concentrations, based on which calibration curves were fitted, providing benchmark sensor array response database, then Bayesian inference framework was utilized to process the sensor array data and build a sample selection program to simultaneously identify gas species and concentration, by formulating proper likelihood between input measured sensor array response pattern of an unknown gas and each sampled sensor array response pattern in benchmark database. This algorithm shows good robustness which can accurately identify gas species and predict gas concentration with a small error of less than 10% based on limited amount of experiment data. These features indicate that Bayesian probabilistic approach is a simple and efficient way to process sensor array data, which can significantly reduce the required computational overhead and training data.

A novel crosstalk suppression method of the 2-D networked resistive sensor array.

The 2-D resistive sensor array in the row–column fashion suffered from the crosstalk problem for parasitic parallel paths. Firstly, we proposed an Improved Isolated Drive Feedback Circuit with Compensation (IIDFCC) based on the voltage feedback method to suppress the crosstalk. In this method, a compensated resistor was specially used to reduce the crosstalk caused by the column multiplexer resistors and the adjacent row elements. Then, a mathematical equivalent resistance expression of the element being tested (EBT) of this circuit was analytically derived and verified by the circuit simulations. The simulation results show that the measurement method can greatly reduce the influence on the EBT caused by parasitic parallel paths for the multiplexers' channel resistor and the adjacent elements.

Chemical Sensor Array Modeling: Application to Resistive Based Chemo Sensors

The aim of paper is to develop analytical mathematical models that describe the thermo dynamical equilibrium of resistive chemical sensor arrays /mixture of vapors multi-system. By using the Gibbs Duhem formalism, state equations in differential form, that the variations of intensive quantities (e.g. sensors partial sensitivity) as function of the gas mixture components concentrations and sensor array parameters describe, have been developed. Moreover, the responses of the sensor arrays as function of gas mixture components concentrations were modeled.

VF-NSE method measurement error analysis of networked resistive sensor array

In this paper, we present a measurement error analysis of the voltage feedback non-scanned-electrode (VF-NSE) method for the 2-D resistive sensors array that shares row and column connections for simplifying interconnections. A mathematical voltage expression for the VF-NSE method has been analytically derived and verified by the circuit simulations, which is affected by the multiplexers’ resistor, the column adjacent elements and the row adjacent elements. Based on this analysis of the VF-NSE method with the sample resistor connected to the voltage source, we examined and proved that the voltage expression is general for analyzing the effect of the multiplexers’ resistor, the column adjacent elements and the row adjacent elements in the networked resistive sensor array.

108 ワイヤーロープ保守用プローブクライマーの性能評価

With the increase in the number of elevator installation, it is important that the accuracy inspection and work efficiency are improved. In this study, in order to develop a remote maintenance inspection system of wire rope for structure, an inspection device was first mounted for evaluating structural integrity and an elevation mechanism (probe climber) was fabricated which was capable of even vertical automatic movements. This study considers the detection accuracy after configuring a sensor system of Giant Magnetic Resistance sensor-array which is more compact and accurate in detection than conventional products describes the evaluation results through experiments for identifying the locations of damage in conjunction with a drive control system of the automatic elevation device. We did experiments probe climber that elevates the wire rope with five concentrated damages to 50cm interval. As a result, it was able to identify the locations of damage and detect concentrated damages.