| 摘要 |
An electrooptical instrument for detecting the presence of liquid and a method of operating the same, comprising at least one monochromatic infrared source, a light conductor which totally reflects infrared radiation from at least one surface thereof, an infrared detector, and signal processing circuitry. According to the invention the infrared source has a maximum radiation strength of less than 200 mW/sterad, the main maximum in the angular distribution of the infrared radiation is at least approximately axially symmetric and oriented in the direction of the optical axis of the light conductor, and the angular distribution of the infrared radiation is such that the intensity falls off to half its maximum value less than 4 DEG away from the symmetry axis. An electronic circuit causes the system to oscillate when no liquid is present. The instrument may be operated in a self-monitoring mode by monitoring the oscillations with two monostable multivibrators connected in parallel. |
