Time difference ultrasonic flow measurement is a common method of ultrasonic heat meter for flow measurement. Its principle is to use a pair of ultrasonic transducers to alternately (or simultaneously) transmit and receive ultrasonic waves, indirectly by observing the time difference between the upstream and backward propagation of ultrasonic waves in the medium. An indirect measurement method of measuring the flow rate of the fluid, and then calculating the flow rate through the flow rate, but in actual applications, the flow rate is affected by different factors, such as: the length of the sound channel, the installation angle of the ultrasonic transducer, the measurement accuracy of the pipe section radius, Signal distortion or loss, the measurement accuracy of the ultrasonic time difference, the temperature change of the measured liquid, etc., will introduce errors to the flow measurement. In order to solve this problem, most of the existing methods are to introduce a correction compensation coefficient, through which the correction compensation coefficient is used to calibrate the flow rate, thereby reducing the measurement error.
However, since the flow correction compensation coefficient is non-linearly distributed within the full-scale flow range, if you want to ensure the accuracy of the flow error within the full-scale flow range, you need to calibrate many flow points to obtain a more accurate correction compensation curve. However, this method will cause very low production efficiency due to more flow points to be calibrated and corrected during production. Therefore, in order to improve production efficiency, most manufacturers reduce the calibration of flow points in the actual production process, resulting in a large difference between the corrected compensation curve and the actual, which cannot guarantee the accuracy of the flow measurement error within the full-scale flow range. At the same time, due to the wide range of water temperature required by the heat meter, the same flow point has different errors at different water temperatures. A single correction compensation curve can no longer guarantee the error of each flow point within the full range of water temperature range, resulting in the flow point at The flow measurement error is not accurate under different water temperatures. The purpose of the present invention is to provide a fast and effective method for correcting the flow measurement error of the time difference ultrasonic heat meter.
The flow error correction method of the time-difference ultrasonic heat meter provided by the present invention includes the following steps: Step one, adopts the method of inter-zone correction: divide the full-scale flow range into three intervals, and select within the full-scale flow range Three basic flow points, the basic flow points are respectively distributed in three intervals; two standard compensation correction curves are set at the same time: one is the standard compensation correction curve for the full-scale flow range under the water temperature of M degrees, and the other is different under the full-scale water temperature The standard compensation correction curve of water temperature to the basic flow point error; step two, the three basic flow points of the ultrasonic heat meter are calibrated and corrected at a water temperature of M degrees, and the flow value before the basic flow point is not corrected, and the error correction compensation coefficient are saved And the water temperature during calibration; step three, according to the error correction compensation coefficient and water temperature during the basic flow point calibration, move the two standard compensation correction curves up or down in sections to obtain the true compensation correction curve of the ultrasonic heat meter Step 4: Obtain the real error correction compensation coefficient according to the two real compensation correction curves, and thus obtain the flow rate of the ultrasonic heat meter.
Figure is a schematic diagram of ultrasonic fluid flow measurement of the present invention
The second step includes the following steps: step 1, take out the original flow rate Q to be corrected and the water temperature T measured this time; step 2, confirm according to the full-scale flow range partition array D[2] The partition number p corresponding to the original Q; Step 3, take out the two-dimensional array C of calibration parameters of the three basic flow points [3] [3] Confirm the original flow Q basis of the basic flow points within the range of p value, and the correction coefficient K base and water temperature T base. The step three includes: obtaining the original array number i corresponding to the Q according to the two-dimensional array A [m] [2] of the standard compensation correction curve in the full-scale flow range at the water temperature of M degrees, and obtaining the corresponding array number i according to the number i Correction coefficient Ka_i; According to the two-dimensional array A [m] [2] of the standard compensation correction curve in the full-scale flow range under the water temperature of M degrees, the array number ii corresponding to the Q basis is obtained, and the corresponding correction is obtained according to the number ii Coefficient Ka_ii; according to the two-dimensional array B[n] [4] of the standard compensation correction curve for the basic flow point error of different water temperatures under the full-scale water temperature, get the array number j corresponding to the T measurement, and confirm the interval range according to the p value The corresponding correction coefficient Kb_p_j is obtained for the basic flow point of the T base; the two-dimensional array B[n] [4] of the standard compensation correction curve for the error of the basic flow point at different water temperatures at the full range of water temperature is obtained. , And at the same time confirm the basic flow point in the interval according to the p value to obtain the corresponding correction coefficient Kb_p_jj.
The error correction compensation coefficient K for any flow point at any water temperature within the full-scale water temperature and full-scale flow range is: K=(Ka_i×Kb_p_j&TImes;K基原)/(Ka_ii&TImes;Kb_p_jj); full-scale water temperature and full-scale flow The corrected flow rate Q measurement at any flow point at any water temperature within the range is: Q measurement = K&TImes; Q original.
The invention only needs to calibrate the three basic flow points at a certain water temperature during production, and can ensure the accuracy of the flow error within the full-scale water temperature and the full-scale flow rate range, thereby greatly improving the production efficiency.
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