Abstract: A water depth measuring method comprises steps of making a bundle of reference water column pressure measuring tubes of a U character form of the number of n≧2 at a same length with a water depth measuring tube in order to compensate for a total error of a water depth measurement; filling an amount of water into the reference water column pressure measuring tubes to form water columns therein; measuring the water pressure in the reference water column pressure measuring tube by a pressure transducer before measuring a water depth; subtracting previously known water column pressure values derived from the measured water pressure values to calculate total error values; calculating a total error based on the total error values, in which the total error was generated upon measuring of the bubble generating pressure in the water column pressure measuring tubes; subtracting the total error from the bubble generating pressure, dividing the calculated water column pressures by the water column pressure in the refe

Abstract: A sonic water level measuring method and system for mounting a wave-guide tube for measuring a water level in a reservoir, a river, etc. generating sonic pulses at the upper of the wave-guide tube, measuring transit times that it takes for the sonic pulses to transit from an original point to a water surface through air medium and transit back to the original point after being reflected on the water surface and multiplying the transit times by a sound velocity to compute a water level is configured to measure the sound velocity using the times that it takes for the sonic pulse to transit in two intervals in order to exactly measure the sound velocity that is changed according to the changing of an air temperature, pressure and component in the wave-guide tube and then measure the water level considering an arithmetical average value of the sound velocities measured as a sound velocity in the wave-guide tube.

Abstract: An ultrasonic flow rate measuring method comprises steps of measuring an inner diameter of a pipe in a manner to subtract a corrosive resistance layer and its possible thickness deviation from the maximum deviation of an inner diameter presented as a pipe size within the range of being able to be estimated, measuring a flow rate QI of the ideal circular section having the measured inner diameter based on the ultrasonic multi-channel flow rate measuring method, calculating a flow rate QII of the remaining section according to a flow velocity distribution curve and adding the flow rate QII to the flow rate QI to calculate a total flow rate Q. Therefore, the method can enhance the accuracy of the flow rate measurement, if the section area of a pipe can't be measured, exactly, and the inner diameter of the pipe has a deviation due to an ovalness.

Abstract: A sonic level measuring method comprises steps of disposing N sonic receivers 51,52,53, . . .

Abstract: An ultrasonic flow measuring method that includes selecting a section area in a right angle to an ultrasonic transit trajectory line for measuring a flow velocity as a section area necessary for a flow measurement; and multiplying a flow velocity component of a direction corresponding to an ultrasonic transit trajectory, which is directly measured by an ultrasonic wave, by the section area thereby to compute a flow or flowrate, so that a flow measuring error and a measuring error of a section area can be significantly reduced, thereby enhancing the accuracy of the flow measurement. The apparatus having a plurality of paired transducers disposed within the pipe at opposing sides; a mechanism for measuring a flow velocity of the fluid for each of a plurality of chords dividing the section area; and a mechanism for determining the flow of the fluid based on a product of the average flow velocity of the fluid and a flow computing area.