Analog to digital conversion using an integrater and a sample and hold circuit
AssigneeLinear Instruments
InventorsJames L. Mills, Louis Hlousek
Life of this patent
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Abstract
An analog to digital signal converter includes an integrator and a sample and hold circuit. Precisely repeatable timing signals for both the integrator and sample and hold circuit are provided by a microprocessor. The device provides low pass filtering without the phase lag normally associated with linear filters. The device allows one set of data to be acquired while the previous set of data is being digitized. The device is especially applicable to analysis of data generated by a spectrophotometer.
Claims15
A device for converting an analog signal to a digital signal comprising:
- integrating means for integrating the analog signal substantially continually;
- sample and hold means for sampling and holding an output of the integrating means;
- control means for providing a plurality of control signals at predetermined time intervals to the integrating means and to the sample and hold means;
- a voltage to frequency converter for receiving an output of the sample and hold means and converting the output of the sample and hold means to a digital signal having a frequency which is a function of a voltage of the output of the sample and hold means and representative of the analog signal;
- and
- a counter for counting the frequency of the digital signal of the voltage to frequency converter.
A method for converting an analog signal to a digital signal comprising the steps of:
- integrating the analog signal substantially continually;
- sampling and holding the integrated analog signal;
- converting the sampled and held signal to a frequency varying signal which is a digital representative of the analog signal;
- and
- counting a frequency output of said frequency varying signal.
A circuit for converting an analog current derived from a photosensor to a digital signal comprising:
- a current to voltage converter for converting the analog current derived from the photosensor to a first voltage substantially continually;
- an integrator for integrating the first voltage substantially continually and providing an integrated voltage, the integrator being rest in response to a first signal;
- a sample and hold circuit for sampling and holding the integrated voltage in response to a second signal;
- a converter for analog to digital conversion of a voltage held by the sample and hold circuit to a frequency varying signal, the frequency varying signal being a digital representative of the analog current;
- a counter for counting a frequency of the frequency varying signal produced by the converter;
- and
- a processor for generating first signals to the integrator at predetermined intervals of time and second signals to the sample and hold circuit at predetermined intervals of time.
Dependencies are inferred from the claim text.