Development of a voltage controlled resistor for use in a self-balancing resistance bridge

A Tadić; A Reyes Borunda; M W Ray

doi:10.1063/1.5119720

Development of a voltage controlled resistor for use in a self-balancing resistance bridge

Rev Sci Instrum. 2019 Dec 1;90(12):124706. doi: 10.1063/1.5119720.

Authors

A Tadić¹, A Reyes Borunda¹, M W Ray¹

Affiliation

¹ Department of Physics and Astronomy, California State University, Sacramento, California 95819, USA.

PMID: 31893857
DOI: 10.1063/1.5119720

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.