D. Patranabis

A novel software-based transducer linearizer

A novel technique for deriving linearized output for specific types of nonlinear transducers using a software package is presented. The method has a low storage requirement and is capable of online operation, particularly for comparatively slower processes. It has the flexibility to incorporate the device specifications and range during operation itself. Appended results show that the performance of the method is adequate for it to be adopted commercially. >

A simple analog divider having independent control of sensitivity and design conditions

A simple, low-cost analog divider circuit using the voltage-variable resistance (VVR) property of a field-effect transistor (FET) is presented. The circuit is useful in signal processing for instrumentation systems. An example application is in linearizing a transducer. Experimental studies of the divider circuit are discussed. A simultaneous multiplier-divider circuit derived from the presented scheme is also discussed. >

True RC integrators with very large and very small time constants using active control of capacitance and/or resistance

Two novel active RC integrator schemes with time-constant enhancement as well as depletion facility are presented. One of the schemes uses a capacitor multiplication technique for time-constant enhancement; the other uses a negative immittance converter to enhance or lower resistance for integrator time-constant control. Both schemes have been tested and the results are found to corroborate the theoretical values. Pertinent discussions relating to their performance have been appended. >

New improved bipolar and bilateral voltage to current converters

Some improved bipolar, bilateral voltage-source-to-current-signal converter schemes, using operational amplifiers (OA) as active devices, are described. Some of them are derived from an earlier scheme that uses the OAs in summing mode, and the others are derived from the conventional technique of using the OAs in current output configurations. Except for one scheme that uses a single OA for the realization, the others have ideal voltage-to-current transfer ratio and characteristics. The realization constraints in each case have considerable degrees of flexibility, and there is no effect of load variation as long as the OAs used in the schemes are not saturated due to increased input conditions. The admittance matrices, constraints of realizations, and sensitivity to passive parameters for the different schemes are tabulated for ready reference. It is shown that the schemes can be used as V-I and I-V converters with scaling facility of the conversion factors. >

A four quadrant multiplier with independent control of range and sensitivity

An improved analog multiplier using the voltage variable resistance characteristics of a FET is presented. The scheme has independent control of the design condition, sensitivity, and range. A modified version, with a marginal increase in hardware but embodying the same operating principles, can work in all four quadrants in both DC and AC operations. The proposed multiplier is superior in performance to earlier schemes based on the same technique. Its design condition is independent of the inputs, unlike the earlier ones. Experimental results and appropriate error analysis are presented. >

Instrumentation for continuous in situ monitoring of water quality

A continuous river water-pollution level monitoring system using a comprehensive instrumentation package coupled with a microprocessor ( mu P)-based data logger and telelink is described. The instrumentation package along with a power supply unit and a mu P-based converter and transmitter set is housed in a floating buoy, and on-shore receiving is effected through another mu P-based system. A retransmission is performed next, and data are received at a station sufficiently remote from the river banks, where the data are stored as well as processed for further use. Bench-level tests and in situ experiments have shown promising results for long-term monitoring of water-quality parameters of a river. >

Circuit for Linear Frequency-Independent Output from a Differential-Capacitance Displacement Transducer

A circuit that provides an output voltage ideally linearly proportional to the displacement for a differential capacitance-type probe is presented. The circuit is very easily modified to have an output independent of the input supply frequency as well. The component imperfection, however, restricts this independence and produces a deviation at lower frequencies. Pertinent discussions are appended.

Active Rc Integrators and Differentiators

The paper reviews earlier works on active RC integrators and their compensation schemes. Some works suggesting enhancement and lowering of integrator and differentiator time constants have also been considered. Some new 2-OA schemes have then been proposed which use one capacitor, either floating or grounded, and which are easily adapted for polarity inversion, capacitor leakage compensation and large time constant generation. Also, schemes have been suggested where integrator and differentiator can be obtained in the same scheme without going for reciprocation. Finally switched capacitor integrators have been briefly discussed. Results of a particular versatile integrator have been given in the photograph of a CRT display.

A Self-Tuning Controller Based on PI Algorithm

A simple self-tuner algorithm based on the tuning of the proportional band of a conventional Proportional Integral mode action is proposed. The algorithm, based on intuitive reasoning as adopted by process experts is simpler than many of its type specially from the viewpoint of implementation on a 8 or 16-bit microprocessor. It has been tested in a stable second order process model as also in an actual second order thermal process. Test results show that the proposed algorithm has an edge over its conventional discrete counterpart even when the latter is perfectly tuned.

Linear Speed Control of Strip-Like Materials with a Variable Slope Current Ramp Excitation

A very elegant method of linear speed control for strip-like materials is presented. When the strip thickness does not vary an open loop system is shown to achieve the objective with a separately excited dc motor drive whose field coil is energized with a current varying in proportion to time. For varying thickness of the strip, feedback is incorporated, resulting in precise and accurate control of linear speed by suitably modifying the excitation current. Simulated results have shown excellent corroboration of the theory. A prototype has then been constructed and a set of results obtained with it has also shown good correspondence with the theory.