A direct resistance-to-digital converter (RDC) that is suitable for differential resistive sensors is proposed and analyzed in this paper. The RDC presented here provides a digital output that is linearly proportional to the parameter being sensed by a differential resistive sensor possessing either linear or inverse characteristics. The RDC employs the sigma-delta analog-to-digital conversion (Σ-Δ ADC) principle and, hence, possesses all the advantages and limitations of such an ADC. Analysis shows that the proposed RDC has negligible sensitivity to variations in circuit parameters. Experimental results on a prototype built and tested gave a worst-case error < 0.15%, establishing the efficacy of the proffered RDC. © 2009 IEEE.

Boby George

Department of Electrical Engineering

Varadarajan Jagadeesh Kumar

ANALOG-TO-DIGITAL CONVERSIONS

CIRCUIT PARAMETERS

DIFFERENTIAL RESISTIVE SENSOR

DIGITAL OUTPUTS

DIRECT DIGITAL CONVERTER

LINEARLY PROPORTIONALS

RESISTANCE-TO-DIGITAL CONVERTER (RDC)

SENSITIVITY TO VARIATIONS

Signal conditioning

WORST-CASE ERRORS

Delta sigma modulation

Force measurement

Multicarrier modulation

Sensitivity analysis

Sensors

strain measurement

Frequency converters

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IIT Madras

Analysis of a Sigma–Delta Resistance-to-Digital Converter for Differential Resistive Sensors

IEEE Transactions on Instrumentation and Measurement

A novel readout circuit for interfacing single element resistive sensors is presented in this paper. The proposed scheme is based on a new relaxation oscillator (RO). The RO, along with a timer counter provides a digital output proportional to the resistance of the sensor. The output characteristic of most of the existing readout circuits for resistive sensors suffers from gain, offset, and nonlinearity errors. The sources of errors include various nonideal circuit parameters and their drift. The output of the proposed readout circuit has a special feature that it is not a function of the circuit parameters such as: 1) offset voltages of the opamps and comparators; 2) bias currents of the opamps and comparators; 3) gain of various units employed; 4) ON-resistance of the switches; 5) value or mismatch in the magnitudes of the reference voltages employed; 6) delay of the switches and comparator; 7) leakage current of the switch; and 8) slew rate of the opamp. Such a scheme will be useful for high accuracy measurements, even when the parameters 1)-8) may vary or drift, due to variation in the measurement environment. A prototype of the proposed readout scheme has been developed in the laboratory and the performance has been evaluated under various conditions. The output was found to be linear with a worst-case nonlinearity of 0.05%. Test results from a prototype developed show that the proposed scheme possesses all the features, described above, as expected. © 2017 IEEE.

A resistive sensor readout circuit with intrinsic insensitivity to circuit parameters and its evaluation

A novel resistance-to-digital converter (RDC), based on the integrating type analogue-to-digital converter principle, is presented in this study. The conversion time of the proposed scheme is not a function of the current value of the parameter being measured. Thus, by suitably setting this parameter, the converter can be made to reject the effects of interference at a particular frequency, such as, that due to power-line at 50/60 Hz. Error analysis was conducted to ascertain the effects of non-idealities of various components of the circuit, on its output. Simulation studies were carried out in LTSPICE to verify the linearity and the interference rejection capability of the converter. Further, a prototype RDC was developed in the laboratory and tested to confirm the results of the simulation. © The Institution of Engineering and Technology.

IET Circuits, Devices and Systems

Resistance-to-digital converter designed for high power-line interference rejection capability

A sigma-delta-type digital converter (SDC) suitable for a resistive-potentiometer-type displacement sensor with a floating slide is presented here. The delta modulator in a conventional SDC is suitably altered to incorporate, as its integral part, a resistive-potentiometer-type displacement sensor with a floating slide. The operation of the 1-b quantizer in the SDC is modified such that the digital output of the SDC directly indicates the displacement being sensed. The results obtained from simulation studies, emulation studies, and experimentation conducted on a prototype sensor establish the efficacy of the proffered scheme. © 2016 IEEE.

Sigma-Delta Digital Converter Suitable for a Resistive Displacement Sensor with a Floating Slide

A new Resistance-to-Digital Converter (RDC) suitable for single element resistive sensors is presented in this paper. The proposed scheme is based on a relaxation oscillator circuit, which along with a timer-counter that measures the time intervals of oscillations, provides digital output proportional to the resistance of the sensor. In most of the existing RDCs, the output characteristic has gain, offset and non-linearity errors owing to various circuit parameters and their drift in the measurement unit. The output of the proposed RDC has a special nature, by the design of the measurement method, that it is not a function of the circuit parameters such as offset voltages and bias currents of the opamps and comparators used, gain of various units employed, ON-resistance of the switches, value or mismatch in the magnitudes of the reference voltages employed, etc. Such a scheme will be useful for high accuracy measurements, even in circumstances where the above-mentioned parameters may vary or drift, due to variation in the measurement environment, say, large variation in temperature. A prototype of the proposed RDC has been developed in the laboratory and the performance has been tested under various conditions. The output was found to be linear with a worst-case non-linearity of 0.06 % As expected, the sensitive of the output of the prototype RDC to various circuit parameters was found to be negligible. © 2016 IEEE.

Conference Record - IEEE Instrumentation and Measurement Technology Conference

A Resistance-to-Digital Converter possessing exceptional insensitivity to circuit parameters

A new, simple and high-accuracy impedance-to-digital converter (IDC) is proposed in this paper. Conventionally, the parameters of sensors that can be modeled using a parallel combination of a capacitor (C) and a resistor (R) are measured using ac bridges, excited from a sinusoidal source. Recently, with the widespread use of digital systems in instrumentation, capacitance-to-digital converters and resistance-to-digital converters gained a lot of importance. An IDC that accepts sensors having C and R in parallel and provides digital outputs directly proportional to the C and R values is presented in this paper. This can be used not only for sensors whose C and R values vary with the measurand but also when C or R of a sensor needs to be measured keeping the output not affected by parasitic R or C present in parallel with the sensing element. Another application of the IDC is in the measurement of the dissipation factor of dielectric materials. The proposed IDC is based on a dual-slope technique, and hence provides high accuracy and immunity to noise and interference. A prototype of the proposed IDC has been developed and tested in the laboratory. Accuracy of the prototype IDC developed was 0.15% for the measurement of C and 0.04% for the measurement of R. The total conversion time of the prototype converter developed is 3 s, and its total power dissipation is 175.8 mW. The IDC was also interfaced with a polymer-based impedance humidity sensor, measured its C and R values for a range of humidity, computed the humidity, and compared its performance with another instrument, showing the practicality of the proposed IDC. © 1963-2012 IEEE.

A Direct Digital Readout Circuit for Impedance Sensors

This paper presents a novel resistance-to-digital converter (RDC) suitable for differential resistive sensors. The proposed RDC provides a digital output linearly proportional to the parameter being sensed by a differential resistive sensor not only for differential resistive sensors possessing linear characteristic but also for sensors possessing inverse characteristic. The proposed RDC is based on the sigma-delta type analog-to-digital converter (Σ-Δ ADC) principle and hence possesses all the advantages and limitations of a Σ-Δ ADC. Experimental results on a prototype built and tested gave a worst case error < 0.15 %, establishing the efficacy of the proffered RDC. ©2008 IEEE.

A sigma-delta resistance to digital converter suitable for differential resistive sensors

Understanding Delta-Sigma Data Converters

2007 IEEE Instrumentation & Measurement Technology Conference IMTC 2007

BandPass Sigma-Delta Modulator for Capacitive Pressure Sensor

Dual Slope Resistance to Digital Converter

Computer Standards & Interfaces

Worst-case uncertainty measurement in ADC-based instruments

Analysis of a sigma-delta resistance-to-digital converter for differential resistive sensors

Journal	IEEE Transactions on Instrumentation and Measurement
ISSN	00189456
Open Access	No