| 摘要 |
<p>PROBLEM TO BE SOLVED: To obtain an electronic distance meter which measures the level of a liquid surface inside a tank containing an inflammable liquid such as, e.g. gasoline, LPG or the like. SOLUTION: An electronic distance meter is provided with a light-emitting element 12 by which radiant light carrying a modulation signal is radiated to a target 18, with a light-receiving element 20 which receives incident light reflected by the target 18 so as to obtain a measured value, with a changeover means, i.e., an automatic disphragm device 28, through which calibration light carrying the modulation signal is received by the light-receiving element 20 via an internal calibration passage having a prescribed length so as to obtain a calibration value and with a control circuit 32 containing a microcomputer which is operated at a low voltage and which computes a distance up to the target 18 on the basis of the measured value and the calibration value. In order to adjust the quantity of incident light from the target 18, an automatic dispphragm device 24 which is operated at a low voltage is used. The automatic diaphragm device 28 is replaced by a second light-emitting element and an electric changeover means. The automatic diaphragm device 24 is replaced by a multiplier which makes the output to the light-emitting element 12 variable.</p> |
