JPH0697178B2 - Flowmeter instrumental error correction method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow meter which transmits a plurality of flow rate pulses per revolution from a rotor which rotates according to the flow rate of fluid, and the error between the actual flow rate of fluid and the measured value is large. The present invention relates to an instrumental error correction method for correcting the display of measured values in the low flow rate range so as to approach the actual flow rate of fluid.

[0002]

2. Description of the Related Art Generally, in a flow meter for measuring an instantaneous flow rate or an integrated flow rate of a fluid, it is necessary to display the measured value in a low flow rate region where the error between the actual fluid flow rate and the measured value becomes large. The instrumental error is corrected so that it approaches the flow rate of the fluid, but with a flow meter that sends multiple flow pulses per revolution from the rotor that rotates according to the flow rate of the fluid, each moment in the low flow rate range The instrumental difference for the flow rate, that is, the correction data, is obtained from the data at the time of verification of the flowmeter and stored in large numbers, and the correction data is called according to the instantaneous flow rate measured each time the flow rate pulse is transmitted. An instrumental difference correction method for performing correction is used.

[0003]

This instrumental error correction method is
Since a large amount of correction data is required, it takes a great deal of man-hours and time to obtain data for flow meter verification, so the instrumental error of flow meters produced in large quantities of the same model is corrected. In this case, the correction data can be applied to flowmeters of the same model, which is an effective instrumental error correction method, but on the contrary, when correcting instrumental error of flowmeters for small-lot production of multiple models, the cost However, there are drawbacks such as an expensive instrumental error correction method. Further, even if the instrumental difference of the same type of flowmeter is compensated by this instrumental error correction method, since the correction data is shared, there arises a drawback that variations in instrumental characteristic of each flowmeter cause an error. There is. Besides, regardless of the type of flow meter,
With respect to changes in instrumental error characteristics due to changes over time in the flowmeter itself, it is necessary to re-verify each flowmeter and obtain a large amount of correction data again, which causes a problem such as being extremely troublesome. ing.

The present invention is intended to eliminate the above-mentioned drawbacks, and stores the instrumental error of several points in the low flow rate region, that is, the correction data, and calculates the correction data for the instantaneous flow rate in the meantime by linear interpolation. As a result, correction data can be obtained over the entire flow rate range, and correction data can be easily obtained even for each flow meter, which is advantageous for both mass production models and multi-model small-quantity production models. An object of the present invention is to provide an instrumental error correction method that can easily cope with variations in instrumental error characteristics due to changes over time.

[0005]

Means for Solving the Problems In a flow meter that transmits a plurality of flow rate pulses per revolution from a rotor that rotates according to the flow rate of fluid, the cycle of the flow rate pulse is measured, and the instantaneous flow rate is calculated from this cycle. Then, it is determined which of the plurality of boundary values the instantaneous flow rate is stored between, and two boundary values between which the instantaneous flow rate is stored and the corresponding boundary values are stored. The correction data corresponding to the instantaneous flow rate is calculated from the other two correction data by linear interpolation, and the instantaneous flow rate or the integrated flow rate is corrected from the calculated correction data.

[0006]

In the above flow meter, the instantaneous flow rate at several points in the low flow rate region and the correction data for matching the measured value and the actual flow rate at that time are stored in advance from the data at the time of verification of the flow meter. After that, when the flow pulse is transmitted from the rotor that rotates according to the flow rate of the fluid, the cycle is measured from two adjacent flow pulses. Furthermore, the instantaneous flow rate conversion value is calculated from this cycle measurement value and the meter factor of the flow meter,
It is determined which two boundary values among the boundary values stored in advance the instantaneous flow rate conversion value is sandwiched between.
When boundary values sandwiching the instantaneous flow rate conversion value are selected, correction data for each of the boundary values and the difference between the boundary value and the instantaneous flow rate conversion value are used to calculate correction data for the instantaneous flow rate conversion value by linear interpolation. The instantaneous flow rate display value is calculated and displayed from the calculated correction data and the instantaneous flow rate conversion value, and the corrected flow rate per unit pulse is calculated from this correction data and the meter factor, and the integrated value is displayed, and the actual value is displayed. The flow rate and the displayed value can be matched. Moreover, in this method, it is only necessary to obtain the correction data for a few points, and the correction data can be easily obtained for each flow meter.

[0007]

Embodiments Embodiments will be described below with reference to the drawings. In FIG. 2, reference numeral 1 is a flow rate measuring unit connected to a flow meter 2 in which a plurality of flow rate pulses are transmitted per revolution from a rotor (not shown) that rotates according to the flow rate of fluid. The flow rate measuring unit 1 includes a storage unit 3 that stores a momentary flow rate at a boundary value and instrumental error or correction data for each instantaneous flow rate, a control unit 4 including a one-chip microcomputer, an instantaneous flow rate and an integration. The display unit 5 displays the flow rate. The storage unit 3 includes correction data for correcting the difference between the actual flow rate at the time of verification of the flow meter 2 and the flow rate obtained from the flow rate pulse number and the meter factor F together with the instantaneous flow rate at several points in the low flow rate region. It is configured to remember. The instantaneous flow rate forms a boundary value of the converted values of the instantaneous flow rate obtained from each flow rate pulse, and the smaller the number of the boundary values, the better, but consider the maximum error according to the fluctuation of the instrumental error in the low flow rate region. The above is configured to be appropriately selected. For example, in this storage unit 3, the instantaneous flow rate at four points (100 l / h, 60 l
/ H, 40 l / h, 20 l / h) and correction data (-0.05%, -0.1%,-) for these instantaneous flow rates.
0.2%, -0.6%) is stored.

Further, as shown in FIG. 1, the control unit 4 a) measures the cycle of the flow pulse each time the flow pulse of the flow meter 2 is transmitted, and obtains a cycle measurement value T. b) The instantaneous flow rate is converted from the cycle measurement value T and the meter factor F of the flow meter 2 to obtain an instantaneous flow rate conversion value x, where x = F / T
Get by. c) From the comparison between the instantaneous flow rate conversion value x and the boundary value, select two boundary values sandwiching this and call the correction data for the two boundary values (the instantaneous flow rate conversion value x is the maximum boundary value, 100
When it is larger than 1 / h, or when the instantaneous flow rate conversion value x is the minimum boundary value, and is smaller than 20 l / h, the correction data P for the instantaneous flow rate conversion value x is the correction for each maximum boundary value or the minimum boundary value. It becomes data. ). d) The correction data P for the instantaneous flow rate conversion value x is calculated from the boundary value, the recalled correction data and the instantaneous flow rate conversion value x by linear interpolation (see FIG. 3). e) The instantaneous flow rate display value M is calculated from M = x (1−P) from the instantaneous flow rate conversion value x and the correction data P corresponding thereto, and this is sent to the display unit 5. f) From the correction data P for the instantaneous flow rate conversion value x and the meter factor F, the correction flow rate V per unit flow rate pulse,
V = (1−P) F is calculated, this is integrated, and the integrated value is sent to the display unit 5 as an integrated flow rate. Is configured.

Further, the display section 5 has a mode switch (not shown), a changeover switch (not shown), an increment switch (not shown) and a decrement switch (not shown). It is configured to switch between the setting mode and the measurement mode.
The changeover switch sequentially calls the instantaneous flow rate stored in the storage section 3 and the correction data for the instantaneous flow rate on the display section 5 in the setting mode, and the increment switch or the decrement switch can change the values of these data. Further, the display section 5 is configured to display the instantaneous flow rate display value M or the integrated flow rate sent from the control section 4 in the measurement mode. It is configured to calculate and display the integrated flow rate from the integrated values of a plurality of correction flow rates per unit flow rate pulse.

In the above flow meter, when a flow pulse is transmitted from the rotor that rotates according to the flow rate of the fluid, every time the control unit 4 receives the flow pulse, the cycle between the flow pulse and the flow pulse transmitted last time is measured. To be done. Further, the instantaneous flow rate is converted from the period measurement value T and the meter factor F, and the instantaneous flow rate conversion value x is compared in order from the larger boundary value of preset boundary values, 100 l / h, whichever 2
It is determined whether or not the boundary values are sandwiched. When the instantaneous flow rate conversion value x is 100 l / h or more of the boundary value, 10
The correction data (-0.05%) corresponding to 0 l / h is recalled. This correction data is set as the correction data P for the instantaneous flow rate conversion value x, and the instantaneous flow rate display value M is calculated from this and the instantaneous flow rate conversion value x as M = 1.0005x,
Next, from the correction data P and the meter factor F of the flow meter 2, the correction flow rate V per unit flow pulse is V =
It is calculated as 1.0005F, which is integrated and the integrated value is displayed on the display unit 5.

The instantaneous flow rate conversion value x is 100 l, which is a boundary value.
Between 100 / h and 60 l / h, 100 l / h, 6
Correction data for each of 0 l / h (-0.05%,
-0.1%) is called, and the correction data P for this instantaneous flow rate conversion value x is calculated by linear interpolation from each boundary value, each correction data, and the instantaneous flow rate conversion value x (see Formula 1). The calculated correction data P and the instantaneous flow rate conversion value x
As described above, the instantaneous flow rate display value M is calculated, and subsequently the corrected flow rate V per unit flow rate pulse is calculated (see Formulas 2 and 3). However, integrated values of the plurality of corrected flow rates V per unit flow rate pulse are calculated, and these are displayed on the display unit 5. For example, when the instantaneous flow rate conversion value x becomes 80 l / h, the correction data P at this time is -0.00075, the instantaneous flow rate display value M is 80.06 l / h, and the correction flow rate V per unit flow pulse is 1. It becomes 00007F.

[Equation 1]

[Equation 2]

[Equation 3]

Similarly, the instantaneous flow rate conversion value x is between the boundary values of 60 l / h and 40 l / h or 40 l / h.
When it is between h and 20 l / h, the correction data (-0.
1%, -0.2% or -0.2%, -0.6%) is called, the correction data P for the instantaneous flow rate conversion value x is calculated, and the instantaneous flow rate display value M and the correction flow rate per unit flow rate pulse are calculated. V is calculated, and the instantaneous flow rate display value M and the integrated flow rate are displayed on the display unit 5 as described above.

The instantaneous flow rate conversion value x is the boundary value of 20 l /
When it is equal to or less than h, the correction data (-0.6%) is called, and this correction data is set as the correction data P for the instantaneous flow rate conversion value x, and from this correction data P, the instantaneous flow rate display value M and the unit flow rate pulse The corrected flow rate V is calculated, and the instantaneous flow rate display value M and the integrated flow rate are displayed on the display unit 5 as described above.

[0014]

As described above, according to the present invention, the correction data for the instantaneous flow rate in the low flow rate range where the instrumental error fluctuates is stored together with the instantaneous flow rate at that time, and these instantaneous flow rates are used as boundary values. When measuring the instantaneous flow rate between these boundary values, the correction data for this instantaneous flow rate is calculated from the two boundary values sandwiching this instantaneous flow rate and the correction data for these, so that the entire flow rate range is calculated. It is possible to match the displayed value on the display with the actual instantaneous flow rate, and moreover, it is only necessary to obtain the correction data for several instantaneous flow rates during flow meter verification, and it is possible to easily obtain the correction data for each flow meter. , There is no need to prepare instrumental error characteristics for each model, and it is not affected by variations in instrumental error characteristics for each flowmeter at all, and instrumental error characteristics due to changes over time Change performs a re-test each time as long seen, there are advantages such as correction data can be easily obtained.

[Brief description of drawings]

FIG. 1 is a flow chart illustrating the present invention.

FIG. 2 is a block diagram showing a configuration of a flow rate measuring unit according to the present invention.

FIG. 3 is a device characteristic curve diagram of a flow meter according to the present invention.

[Explanation of symbols]

 1 Flow rate measurement unit 2 Flow rate meter 3 Storage unit 4 Control unit 5 Display unit

Claims (1)

[Claims] 1. A flow meter, which transmits a plurality of flow rate pulses per revolution from a rotor that rotates according to the flow rate of a fluid, measures the cycle of the flow rate pulse, calculates the instantaneous flow rate from this cycle, and calculates the instantaneous flow rate. It is determined which of the plurality of boundary values the flow rate is stored in advance is sandwiched between,
The correction data corresponding to the instantaneous flow rate is calculated by linear interpolation from the two boundary values sandwiching the instantaneous flow rate and the two correction data stored corresponding to the boundary values, and the fluid correction value is calculated from the calculated correction data. An instrumental error correction method characterized by correcting a flow rate.