| 摘要 |
<p>Potentiometer whose resistance is varied by a light beam falling on a photo - resistive surface. The potentiometer has no adjustable electrical contact on the resistance surface and minimises the ageing process normally associated with photo - sensitive resistors. The series resistance to the potentiometer is also minimised. The design is based on the use of a resistive track which has several parallel paths exposed to the light spot (26) at any setting position. The resistor form may be linear or circular and has a band of photo-sensitive material (22) laid parallel on a substrate (20) to a similar band (21) of comparatively high resistance, both bands being by interdigitised Indium or Tin conductors (23, 24) such that the light spot covers several such groups at any one time.</p> |
