S. Kaliyugavaradan

Bio: S. Kaliyugavaradan is an academic researcher from Anna University. The author has contributed to research in topics: Ćuk converter & Resistor. The author has an hindex of 1, co-authored 1 publications receiving 51 citations.

A linear resistance-to-time converter with high resolution

Abstract: A resistance-to-time converter employing a bridge amplifier, an integrator and a comparator is described. While possessing a resolution and linearity of the same order as that of a recently reported resistance-to-frequency converter, the present circuit has the advantage of grounded detecting resistance. Further, no compensation arrangement need be incorporated for maintaining wide-range linearity.

Improved Single-Element Resistive Sensor-to-Microcontroller Interface

Abstract: Direct resistive sensor interface to a microcontroller has several advantages but has one prominent disadvantage, namely, the measurement is affected by the resistances of: 1) wires that connect the sensor to the port pins and 2) the internal resistances of the port pins of the microcontroller. A direct sensor-to-microcontroller interface scheme that compensates the effect due not only to resistances of lead wires but also the effect of microcontroller port pin’s internal resistance and any offset present in those pins is presented in this paper. Since the resistances of lead wires are compensated, automatic temperature compensation (temperature effect of lead wires) is also obtained. Simulation study and results obtained from a prototype built and tested establish the efficacy of the proposed method. A maximum error of 0.06% was observed from the prototype developed, when it was tested under room temperature, after interfacing it with the sensor Pt100, with a lead wire resistance $R_{\mathrm {LD}} = 21~\Omega $ . The error increased to a maximum of 0.08%, when the $R_{\mathrm {LD}}$ varied from 0 to $100~\Omega $ . When the same prototype was tested under elevated room temperature of 30 °C to 100 °C, the maximum error observed was 0.18%.

Relaxation Oscillator-Based Active Bridge Circuit for Linearly Converting Resistance to Frequency of Resistive Sensor

Abstract: An easily implementable signal conditioning circuit for resistive humidity and temperature sensors is presented. It is based on a relaxation oscillator in which both the frequency and the duty-cycle of the square-wave output signal simultaneously carry information from two different types of sensors. The output frequency is linearly related to the resistive unbalance of an active bridge, whereas the duty-cycle is independently controlled by a thermal sensor for controlling temperature error of the humidity sensor (RH). The design, analysis, and experimental characterization of the circuit and its application to a sol-gel thin film porous γ-Al2O3-based humidity sensor and resistance temperature detector are reported. Experimental results confirm the theoretical value predicted. The circuit covering wide resistance measurement range has the potential for remotely monitoring measurement parameters accurately.

Analysis of Power-Supply Interference Effects on Direct Sensor-to-Microcontroller Interfaces

Abstract: This paper analyzes the effects of power-supply interference on direct sensor-to-microcontroller interfaces based on measuring the charging/discharging time of an RC circuit that includes the sensor. Power-supply interference becomes a source of trigger noise that affects the measurement of the charging/discharging time and, hence, the measurement of the sensor resistance or capacitance. The measurement uncertainty increases proportionally to the amplitude of the interference and depends on its frequency. Such interference effects are smaller when measuring the discharging time and can be further reduced by placing an additional resistor in the interface circuit. Experimental data obtained from a PIC microcontroller agree with the theoretical predictions

Linearization of NTC Thermistor Characteristic Using Op-Amp Based Inverting Amplifier

Abstract: A low cost linearizing circuit is developed, placing the NTC thermistor in a widely used inverting amplifier circuit using operational amplifier. The performance of the system is verified experimentally. A linearity of approximately ± 1% is achieved over 30 °C -120 °C. When used for a narrower span, a much better linearity of ± 0.5% is obtained. The gain of the arrangement can be adjusted over a wide range by simply varying the feedback resistance. The simplicity of the configuration promises a greater reliability, and also curtails the deterioration in the stability of performance, by reducing the cumulation of drifts in the different circuit components and devices.

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

Abstract: 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 (Sigma-Delta 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.