Sensor circuit for controlling flow in an instrument loop

Details Sensor circuit for controlling flow in an instrument loop Sensor circuit for controlling flow in an instrument loop

1990-11-28

1992-12-08

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Photocell controlled circuit

250214A, G05F 156, H01J 4014

Patent

active

051700352

ABSTRACT:
A circuit for controlling current flow in an instrumentation loop includes a light sensor receiving impinging light and delivering a signal varying with the intensity of the impinging light. The signal is amplified and produces a reference signal which is a current signal of about four milliamperes in the absence of incoming light and about twenty milliamperes in maximum light. A voltage controlled current driver presents an impedance to current flow through the loop which varies with the reference signal and with the intensity of the incoming light. The sensor includes a mounting plate, a photodetector mounted on the mounting plate, a filter mounted over the photodetector, and a diffuser mounted on the mounting plate forming a dome over the filter and photodetector. The diffuser disperses incoming light before the incoming light impinges the photodetector. The filter blocks infrared light thereby blue enchancing impinging light to approximate the light sensitivity response of a human eye. The sensor circuit uses a photovoltaic cell and an amplifier to obtain an output that is linearly proportional to the light level.

REFERENCES:
patent: Re33205 (1990-04-01), Blake
patent: 3709615 (1973-01-01), Blakeslee et al.
patent: 3976875 (1976-08-01), Engstrom et al.
patent: 4135116 (1979-01-01), Smith
patent: 4538063 (1985-08-01), Bulat
patent: 4656353 (1987-04-01), Thompson
patent: 4742574 (1988-05-01), Smith et al.
patent: 4926340 (1990-05-01), Goetzinger et al.

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