Communications: electrical – Audible indication – Percussion-type sound producer
Patent
1976-03-10
1978-04-04
Miller, Charles D.
Communications: electrical
Audible indication
Percussion-type sound producer
340347NT, H03K 1320
Patent
active
040830446
ABSTRACT:
In a unipolar version of an analog-to-digital converter of low-level signals involving a self-zeroing current-to-frequency converter, which virtually eliminates the effects of voltage offsets at the input to the converter while avoiding large leakage currents, improved circuitry is provided in order to avoid paralysis of the converter which could be caused by small input currents or charges of polarity opposite to that of the normal signal current or by drifts in the converter input voltage which produce a negative-charge offset. The circuitry includes provision for the automatic introduction at the converter input of a relatively-large restoration current with the same polarity as the signal current, and this current can also be used for converter checking and calibration. One version of this circuitry involves exposing a junction diode at the converter input to light, causing it to act as a photodiode. One easily controlled source of such light may be a light-emitting diode conducting a suitable current placed in close proximity to the junction diode within the same enclosure. When the junction diode forms a part of a secondary feedback loop used during the discharge period of a primary capacitive feedback, then exposing it to light speeds up the secondary feedback, thereby reducing converter dead time. Other devices may be used for current introduction at the converter input, including a mechanical switch, but they are less preferable from the standpoint of leakage current, size and speed of response.
REFERENCES:
patent: 3688305 (1972-08-01), Goldsworthy
Rogers "The Review of Scientific Instruments" vol. 34, No. 6, June 1963, pp. 660-663.
Furuta "The Review of Scientific Instruments" vol. 41, No. 1, Jan. 1970, pp. 11-15.
Harrington Timothy M.
Marshall, III J. Howard
Doble Arthur V.
MDH Industries Inc.
Miller Charles D.
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