| 摘要 |
<p>A measuring apparatus in the form of a pressure gauge includes a pointer movable over a dial. An adjustable set point forms part of an arm which can move around the dial and carry with it a plastics housing in which are mounted an infrared emitting diode and a silicon photodarlington transistor. The pointer has an end portion which reflects the infra-red radiation from the diode to the transistor when the pointer is in alignment with the set point. The set point is movable around the dial by means of a friction roller which engages the periphery of an annular disc attached to the arm.</p> |
