A current source (52) with adjustable temperature compensation in which the level of current supplied to a load (51) is adjusted to compensate for the load's inherent change in performance with changes in temperature. The current source (52) allows selection of the appropriate temperature compensating characteristic and operating current solely by altering internal component values.

Current source with adjustable temperature variation

Apparatus for determining the content of moisture or other substance in a material by measuring its relative reflectance at two infrared wavelengths. A chopped radiation beam is produced by arranging a tuning fork such that an oscillating element alternatively moves first and second spaced optical bandpass filters having first and second passband wavelengths into position to intercept a beam of source radiation. The chopped beam is directed on the material being analyzed, and radiation reflected therefrom is applied to a radiation detector. The relative transmittances of the filters at their passband wavelengths are such that the radiation detector generates alternating pulses of equal amplitude for a material having a specified content of the substance. The tuning fork also includes a third filter of zero transmittance which periodically interrupts the beam of source radiation so that the detector provides a background signal which is used to correct the amplitudes of the alternating pulses. The alternating pulses are separated and applied to a ratio-determining circuit. The output from the detector is also applied a feedback circuit regulating the temperature of the detector.

Infrared moisture measuring apparatus

A preamplifier network or circuit for converting non-linear signal information, such as is produced by a mercury cadmium tellurium (MCT) detector, to a substantially linear voltage signal output corresponding to the incident light levels on the MCT detector Conceptually speaking, the subject preamplifier functions as a constant-voltage variable-current source to the MCT detector, and incorporates positive feedback for being effective as a negative resistance to nullify the MCT detector resisance introduced signal component of the signal information being monitored

Detector preamplifier for use with a MCT detector

Gain of a photosensitive avalanche member, such as an avalanche photodiode, is stabilized so that a variation in gain of the photosensitive member in terms of temperature is compensated for by applying to the photosensitive member a bias voltage varying with temperature according to a predetermined relationship. The relationship depends on the variation with temperature in the voltage applied to terminals of at least one diode. The gain stabilizing device comprises a temperature-stabilized voltage source, a dc-dc voltage converter having an adjustable gain for applying a bias voltage to the photosensitive member, and at least one diode series-connected between the supply source and an input of the converter.

Device for stabilizing gain of a photosensitive avalanche member

of EP0594012Method and radiation sensor for detecting radiation, in particular light. The change in the physical properties of the electronic components is compensated. Pairs of values are stored in a memory in accordance with the input signal (4) and the output signal (5) of an amplifier (3), or relationships between two signal values are stored. The output signal (5) serves as a measure of the received radiation. For the purpose of compensation, at specific times in the sequence the output signal (5) and the input signal (4) are compared as a pair of values - or in its relationship - with the stored pair of values relating to the respective input signal (4) of the variable which is in agreement. In the event of a deviation in the output signal, the latter is matched by means of appropriate loading of the amplifier (3) to the value of the output signal (5) which is assigned to the input signal (4).

Method for the detection of radiation and radiation sensor.

A temperature compensating circuit for a photoconductive cell whose resistance R varies with temperature and whose responsivity is a function of cell resistance. The circuit includes a transistor connected to the cell to provide a constant bias voltage thereacross so as to provide compensation for an R2 resistance dependence of cell responsivity. A positive feedback circuit for the transistor controls the transistor conduction as a function of cell resistance to cause the transistor to change the level of the cell bias voltage to provide compensation for a resistance dependence of cell responsivity in excess of R2, and more specifically between R2 and R3.

David Coleby Peter Rodney

Papers

Temperature compensating circuits for photo-conductive cells

Temperaturkompensationsschaltung fuer eine Photowiderstandszelle