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Updated: Dec 31, 2025

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Published on: September 30, 2014
Development of a voltage controlled resistor for use in a self-balancing resistance bridge
A Tadić1, A Reyes Borunda1, M W Ray1
1Department of Physics and Astronomy, California State University, Sacramento, California 95819, USA.
Abstract:
We report on a simple design for a voltage controlled resistor that can operate in a continuous range from ∼50 Ω to over ∼100 kΩ. The device consists of a light emitting diode (LED) placed near a photocell. Varying the voltage across the LED changes its brightness, which, in turn, changes the resistance of the photocell. The resistance of the photoresistor is measured by calibrating the output of a nearby phototransistor against the photoresistor resistance, allowing for an independent measurement of the resistance. The performance of the device is tested in the context of a temperature measuring system involving a Wheatstone bridge.
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