A Light Differential Amplifier as a Core of a Speed Measuring System

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A Design of a Special Light Differential amplifier [ First Photo], originally designed to Detect Direct Light and Filter Out the Reflected Light from the Sky [ the primary function of which was to Orientate a Solar Collector by Locating and Tracking the Sun”], was specially designed for incorporation into a conceptual “SPEED MEASURING SYSTEM” for testing speeds of air-engines’ nozzle actuators, in the lab.

The system measured TIME and for a given LENGTH of a Moving Blade attached to and moved with a nozzle actuator Rod, covering/uncovering one of two [drilled on a metal flat plate] holes, under which correspondingly two Photoconductor Sensors were housed [Second Photo], changing thus the state conditions of the amplifier from 0 to 1 and back from 1 to 0 and so triggering the Timer Counter to off/on/off operation recording the Lapsed TIME.

The speed was simply found by dividing the lapsed TIME recorded by the standard LENGTH of the blade used [actually two such blades were used of different sizes].The MINIMUM TIME requirement [and achieved by this simple system] was 80 % of a SECOND.
The system conceptual invention was requested by my Company for me to undertake. I proposed a by-product form ,of my Solar Tracking System which was acceptable [ Shown in the Third Photo with Amplified the yellowish box, and in the Video-Clip ].
Final Drawings incorporated, apart from the Light Differential Amplifier Electronics, the Electrical and Mechanical Components and Devices including a Timer Counter [incorporated on the used Main Fuel Control Test Stand] and a Torch to Beam Directly Light [in excess of the lab normal lighting] on the two holes drilled on the metal plate under which the two sensor photoconductors housed.

The short VIDEO-CLIP released [ and presented by me to a Conference of the Technical Chamber of Greece in 1993 titled “SENSORS 93”] by Special Permission of the Hellenic Aerospace Industry S.A. Management, after my request [as I had LEASED it to my Company FREELY]] bearing in mind that patents of my own were held valid at the time, and Company’s Final Drawings depicted my name and patents.

The amplifier [including the photocells’ housing] was given back to me, on my retirement as the particular programme used it had finished.

This is an occasion for me to thank all Departments of my Company and assisted Colleagues.


Personal info: http://www.stefanides.gr

Patents: expired.



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    Panagiotis Stefanides
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