| 摘要 |
A method of measuring the level of liquid in a flow path comprising the steps of: locating an ultrasonic sensor 12 above a water level 31 at one end of a sonic path, the opposite end of the sonic path to the one end being at a reference level 33 in the flow path (located below the water level); positioning a datum element 18 at an intermediate position in the sonic path; establishing the datum height A between the datum element and the reference level by surveying means; using the sensor to measure the datum range B between the sensor and the datum element; establishing the standing distance C between the sensor and the reference level by adding the datum height to the datum range; mechanically withdrawing the datum element from the sonic path; using the sensor to measure the distance E of the water level from the sensor and thereafter establishing the water level D relative to the reference level by subtracting the distance of the water level from the standing distance. The apparatus compensates for changes in the velocity of sound in air and reference is given to measuring the height of a river above the level of a weir. The disclosure refers to apparatus for undertaking the method and for a remote monitoring installation to be supplied with information from at least one such apparatus. <IMAGE> |
