Constant Current Generator Research Articles

Instrumentation for an electrocutaneous communication device

The device described is a prototype that uses spatiotemporal resolution for electrocutaneous stimulation. Signals initiated through a keyboard activate a matrix of four electrodes that may be applied to the fingers, forearm, abdomen, back, or other parts of the integument. The instrumentation described includes a pulse generator, the active time and delay time controls, the control of the total length of a pulse train, and the constant-current generators whose output is fed into the electrodes. This device may be used as an interface with an alphanumeric device (e.g., a calculator or computer) and as a basic instrument in research investigating the spatial and temporal resolving capacities of the skin senses.

An electric tooth pulp vitality tester.

A simple battery-powered constant-current pulse generator able to supply up to 200 μA at a maximum of 250 V is described. The tester incorporates a battery status indicator and an overload, incorrect operation and fault condition audible alarm. A simple test routine helps to ensure that the instrument is operating correctly before each application. For enhanced patient co-operation and comfort the tester is activated by the patient.

A high-voltage constant-current generator

The apparatus can supply currents from 50 mu A to 4 mA with an output voltage up to 4 kV, suitable for very high impedance loads, much greater than 1 M Omega , such as the electrolyte cells used for moving boundary transference work.

Possible origin of transient dusk‐to‐dawn electric field in the nightside magnetosphere

Development of the electromagnetic field in the magnetosphere‐ionosphere system is examined under the condition that a constant current generator supplies current to the system after t=0. It is shown that at high altitudes there are intervals when the electric field is transiently directed opposite to the direction of the supplied current. Namely, transient dusk‐to‐dawn electric field can be generated from ionospheric channeling of the dawn‐to‐dusk tail current during an early stage of the development of the tail‐ionosphere current system. Electric field with the opposite polarity is produced during intervals when the field reflected from the ionosphere dominates over the incident field.

A wide-range, constant-current generator for use with Hall measurements

A simple design is described for a constant-current generator that covers seven orders of magnitude of current (5*10-10-5*10-3 A) and may be operated with high insulation from earth.

A radioactive current generator for routine calibration of electrometers

A constant current generator using a 90Sr + 90Y beta ophthalmic applicator on a miniature Faraday cup is suggested for routine calibration of electrometers and other high impedance low current measuring instruments.

A PTC thermistor bistable circuit with controllable hysteresis

A novel thermal bistable circuit which consists of a positive temperature coefficient (PTC) thermistor and a constant current generator has two stable states with low and high output voltage level. When the temperature or velocity of a surrounding fluid exceeds a critical value, the circuit is triggered and it rapidly changes its stable state. Both triggering levels of an input thermal quantity can be continually adjusted by circuit parameters. The thermal parameters of the fluid (for instance temperature, thermal conductivity or velocity) and a defined duration of power supply interruption may be detected and memorized.

Differential temperature measurements in engine fluids

IN AIRCRAFT TESTING, it has been difficult to accurately determine small differential temperatures in mediums such as engine oils and aircraft fuels which may vary in temperature over several hundred degrees. A method of measuring this temperature with an electronic circuit utilising platinum probes is presented which is capable of measuring temperature differentials as low as 2.5°C. This method utilises two platinum element probes connected in series driven by a constant current generator. An electronic circuit holds the mid‐point of the probes at virtual ground minimising common mode voltages across the probes. A differential amplifier provides an output proportional to the differential temperature. The mis‐matching and non‐linearity of the platinum sensors is compensated. Voltage sensed across one probe provides an output proportional to the temperature of the medium.

A high voltage capability galvanostat

A constant current generator is described which can supply 10 mu A to 5 mA in 10 mu A steps up to 5 kV with an impedance much greater than 1 G Omega . It is very suitable for use in moving boundary transference work.

A Symmetric Triangle-Square Waveform Generator Using a Single Constant Current Source

A symmetric and accurate triangular waveform generating circuit is described. A simple approach in maintaining the symmetry and linearity of triangular waveform is made by using a single constant current generator to alternately charge and discharge a capacitor in a linear manner. This features perfect symmetry of the waveform over a wide frequency range while maintaining amplitude constancy. The circuit also provides square waveforms of equal on and off periods with rise and fall times of the order of a few nanoseconds. Continuous variation of frequency of the waveform generated is possible by changing a single parameter and it is feasible to have linear, exponential, or logarithmic modulation of frequency. It can be used as a triangle-square waveform generator and as a triangle-to-sine converter with the addition of a few components.

Technique for the measurement of pyroelectric coefficients

A technique is described which can be used for the determination of pyroelectric coefficients in polar crystals. The procedure is based on a simple relationship derived from an equivalent circuit which regards the material as a constant current generator. The measured coefficient is free from contributions arising from tertiary pyroelectricity when special precautions are taken, by the proper design and adjustment of the specimen heaters, to minimize non-uniform heating.

A very high resistance current source for micro-electrophoresis

The article describes a constant current generator with an internal resistance of 10 GΩ and a maximum current capability of ±200 nA on a 100 MΩ electrode. Monitoring the glass electrode resistance is possible without stopping the experiment. The current can be switched on by an external pulse generator.

An electronic constant current shock generator for low current levels

A simple, low cost electronic shock generator capable of producing constant current 60 Hz square wave outputs between 15–200 μA is described. The unit is designed using a penta-grid converter tube which regulates extremely well at low current levels. A circuit diagram is included along with a detailed description of the performance characteristics of this generator. The unit is capable of maintaining a constant current across an animal even when the animal's resistance alters radically as when shock is applied to a moving animal through a grid. The unit is extremely useful in obtaining sensory or motivational thresholds in small animals.

Measurement of the avalanche breakdown characteristics of bipolar transistors†

A transistorized constant current generator suitable for measuring the avalanche mode characteristics of a bipolar transistor has been developed. The generator output current covers the range 0-50 MA, and the current remains constant as the supply voltage is varied from 0.75 v up to several hundreds of volts. The generator may also be used for static characteristic measurements on a wide range of semiconductor devices.

An inherent problem in certain constant-current stimulators

A basic and potentially dangerous problem that may occur in the use of triggered constant-current generators for stimulation is discussed in the general case. A solution with schematic illustration is presented for one specific constant-current generator, the CCS-1A manufactured by Electronics of Life Sciences, Inc.

Conductance changes associated with receptor potentials in Limulus photoreceptors.

The receptor potential in Limulus photoreceptors appears to be a consequence not of permeability changes in the cell membrane but of alterations in a light-sensitive constant-current generator.

Pyroelectric U.V. radiation dosimetry

A dosimetric procedure is described which makes use of the pyroelectric properties of ZnS. The measured polarizations are governed by the pyroelectric co-efficient as well as the internal resistance of the specimen. The latter is diminished, in the course of heating, by electrons released from traps previously filled by the incoming radiation. The behavior of the system is analyzed in terms of an equivalent circuit which regards the material as a constant current generator. Comparisons with thermoluminescence and current-glow processes are described.

Fundamental limitations of EHD energy converters

An EHD energy converter is a high voltage device that converts the kinetic energy of a moving gas stream into electrical energy. This converter has an optimum load requirement for maximum power output. For load resistances larger than this optimum, it behaves as a constant voltage generator. For values smaller, it behaves as a constant current generator. These nonoptimum values are detrimental to the converter.

Functional bulk semiconductor oscillators

This paper describes the generation of various waveforms with bulk semiconductor (Gunn-effect) oscillators having non-uniform cross sections or connected to external resistive circuits by means of small contacts attached to the bulk between the cathode and anode. In nonuniform oscillators, if the variation of the cross section is gradual, a high-field domain is equivalent to a constant current density generator moving at constant velocity. From this simple model, oscillating current waveforms are closely related to the cross-sectional area of the device. The oscillating frequency can be tuned or switched by the bias voltage. In multiterminal oscillators, the cathode current changes whenever a domain passes one of the small contacts connected to the external circuit. The waveforms can be controlled by changing the external circuit parameters. The characteristics of these devices operating in the frequency range from 50 to 150 MHz were extensively studied by changing both the device configuration and the external resistances.

Electrochemical oxidation of some aromatic amines in acetonitrile medium: III. 4,4′-Diaminodiphenylamine, its N-methyl derivatives, and tris-(4-dimethylaminophenyl)amine

The polarographic behavior of 4,4′-diaminodiphenylamine and of its methylated derivatives [4,4′-bis(dimethylamino)- N-methyldiphenylamine; 4,4′-bis(dimethylamino) diphenylamine; 4-dimethylamino-4′-aminodiphenylamine; 4,4′-(diaminodiphenylamine)] and of tris(4-dimethylaminophenyl)amine has been studied in acetonitrile medium on the rotating platinum electrode, and the possibility has been shown of utilizing the oxidation waves of these substances for their polarographic determination, taking into account the influence of water contained in the solvent and acidity of the medium. Constant current coulometric generation has been used to study the number of electrons exchanged in the reaction. The discussion summarizes the conclusions following from Parts I–III of this series and the relations between the polarographic behavior and structure of the reacting substances are discussed.