Beckman Industrial Corporation

Eastman-Kodak Company

Donald F Kaiser

Lee F Frank

Improved accuracy in solution conductivity or resistivity measurment uses a center-sampling technique in which an AC drive is applied to a conductivity cell and the conductivity cell voltage is sampled during a predetermined time interval in the center of a half cycle drive waveform. The effects of cell capacitance, and particularly the electrode-solution capacitive, are compensated by periodically sampling during a second time interval which is different from the first interval. Based upon the difference between the sampled voltages in the first and second intervals, a correction to the measured conductivity or resistivity is made to compensate for capacitance induced errors.

Technique of compensating for capacitive effects in conductivity

Apparatus for generating a constant current, comprising a storage device for storing a voltage corresponding to the constant current, the storage device including a resistor-capacitor filter and having an input and an output; a Zener diode for supplying a constant voltage; a first high off-state impedance device for connecting the Zener diode to the input in response to a first actuation signal; a second high off-state impedance device for connecting the input to a source of discharge potential in response to a second actuation signal; a microprocessor for supplying the first actuation signal to the first high off-state impedance device for a first time interval and the second actuation signal to the second off-state impedance device thereafter for a second time interval, and then providing no first and second actuation signals for a third time interval much greater than the combined first and second time intervals; and a voltage-to-current converting circuit connected to the output and having a high input impedance, for converting the voltage stored in the storage device to the constant current.

Microprocessor controlled constant current circuit

A film video player for producing a standard television signal from photographic film includes an image sensor for sensing a film image illuminated by a pulse of light from an electronic strobe light. The electronic strobe light includes a high voltage power supply with a voltage greater than the minimum ignition voltage of a flash tube in the strobe light for igniting an arc in the flash tube, a low voltage power supply having a voltage less than the minimum ignition voltage of the flash tube for producing an extended pulse of light of constant intensity, means including a photocell for sensing the quantity of light produced by the flash tube and including a control device in series with the flash tube for terminating the pulse of light after a predetermined quantity of light is produced, and means for dispersing the light from the flash tube to produce more uniform illumination. The film video player has the advantage of providing a video signal free from visible flicker, of uniform intensity, and constant color balance. A further advantage is that the video player generates very little heat from its electronic strobe light source and therefore requires minimal cooling.

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Parsippany, NJ, United States of America

Donald F Kaiser