JPS61253430A - Coefficient setter - Google Patents

Abstract

PURPOSE:To achieve a higher accuracy in the measurement of flow rate, by setting and memorizing an instrumental curve beforehand while a reference value is set with a reference setter to determine counts of flow rate by addition and subtraction between the reference value and deviation. CONSTITUTION:A coefficient setter is made up of a Schmitt trigger circuit 1, a correction factor memory unit 2, a control unit 6, an N bit shift register unit 7, an N division correction factor deviation selection unit 9, a setting unit 11, an addition/subtraction unit 12 and the like. A correction factor address is selected with the N division correction factor deviation selection unit 9 according to the current flow rate and sent to the correction factor memory unit 2 through the adder/subtractor 12 to perform a correction according to the instrumental error characteristic. When the instrument error characteristic curve little changes in the long-term service or the like, the reference value is set optimum for the instrumental error characteristic with the setting unit 11 to calculate the flow rate coefficient according to the flow rate thereby enabling highly accurate measurement of flow rate.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coefficient setter for changing reference values for instrumental error characteristics of a flowmeter through subsequent tests.

The weight of the flow rate of the flow rate pulse emitted from the Shimeigougisei flowmeter, that is, the flow rate coefficient, changes depending on the flow rate, and the change in the flow rate coefficient with respect to the flow rate indicates the instrumental error characteristics of the flowmeter. However, since this instrumental error characteristic has excellent reproducibility, the flow coefficient is corrected according to the flow rate based on this instrumental error characteristic, and the applicant has proposed a correction device for this purpose. This correction device transmits a fixed number (K) of clock pulses each time a flow rate pulse is transmitted, and from these clock pulses, it adds or subtracts the correction amount for that flow rate according to the instrumental error characteristics, and then makes corrections. The subsequent clock pulse is divided by the number of clock pulses to generate a corrected flow rate pulse that is approximately synchronized with the flow rate pulse.

However, in the above correction method, first, the instrumental error characteristic is n
Divide it into sections and store each section in an EPROM, etc., select the address of the EPROM corresponding to this flow rate according to the flow rate obtained by converting the flow rate pulse into analog, and set the correction amount corresponding to this address. , K clock pulses through a rate multiplier.

In the conventional method where the number of days is 6 or more, the number of divisions n of the instrumental error characteristic is
If you increase , the correction will be correct accordingly.

However, on the other hand, this results in a corresponding increase in the amount of memory, but if the instrumental error characteristics change over the long term, the number of divisions n
Attempts to make the correction more accurate by increasing the number of errors become meaningless, and there is a problem in that it also requires a lot of effort to correct the writing of the EPROM.

In order to solve the problems in the prior art described above, the present invention has the following steps:
According to the statistics of the secular change of the instrumental error characteristics of the flowmeter, it is simple and
This is to perform accurate correction.

Looking at changes in the instrumental error characteristics over time, in positive displacement flowmeters, the instrumental error characteristics deteriorate in the low flow range, but the characteristic curve does not change much and tends to move in parallel, whereas in the case of estimation type flowmeters, it tends to shift in parallel. There are many cases where the reference value moves due to the influence of piping, but the instrumental error curve does not change.

The present invention utilizes the above-mentioned tendency, and the instrumental error curve, that is, the deviation from the reference value, is set and stored in advance, and the reference value itself can be set by a reference value setting device. Therefore, the instrumental error characteristic is a combination of the reference value and the deviation. That is, by adding and subtracting the reference value and the deviation, a flow rate coefficient at the constant flow rate is obtained, which becomes the weight of the flow rate other than the flow rate pulse, and is corrected for each flow rate pulse. In this case, it goes without saying that if the reference value is provided in units such as the flow coefficient ec/Q, the deviation must also be given in the same units as cc/Q.If the deviation is expressed as %, etc. If it is a dimensionless quantity, it is necessary to add a conversion function to convert it to the same unit.

FIG. 1 is an electric circuit diagram for explaining one embodiment of the present invention, in which 1 is a Schmitt trigger circuit, 2 is a correction coefficient storage unit, 3 is a counter unit, and 4 is a frequency divider (1
/N), 5 is a buffer, 6 is a control unit, 7 is an N-bit shift register unit, 8 is a par display section, 9 is an N-divided correction coefficient deviation selection unit, 10 is an arithmetic unit, 1
1 is a setting unit (semi-fixed correction coefficient), and 12 is an addition/subtraction unit.

FIG. 2 is a diagram showing a time chart of the control unit 6 shown in FIG. 1. As shown in the figure, the gate circuit is opened by the signal A, and the input pulse (pulse proportional to the flow rate in the divided section) is transmitted to N bits. The output of the N-bit shift register unit 7 is latched into the N-divided correction coefficient deviation selection unit 9 by the signal B, and the N-bit shift register 7 is reset by the signal C to select the N-divided correction coefficient deviation. Select the correction coefficient address corresponding to the flow rate from unit 9 at that time.

The signal is sent to the correction unit 2 via the addition/subtraction unit 12, and correction is performed according to the instrumental error characteristics.

Although the correction device described above has a sufficient correction function under certain conditions, the instrumental error changes due to long-term use or the influence of piping, etc.
In that case, the instrumental error characteristic curve hardly changes, and only the reference value changes.

The present invention was made based on the above-mentioned discovery, and in FIG. 1, a setting unit 11 is added according to the present invention, and the reference value for the instrumental error characteristic can be changed by the setting unit 11. This is how it was done.

Effects As is clear from the above description, according to the present invention, the reference value of the instrumental error characteristic can be reset to the optimum value by the setting unit, so that more accurate flow rate measurement is possible.

[Brief explanation of drawings]

FIG. 1 is an electric circuit diagram for explaining one embodiment of a coefficient setter according to the present invention, and FIG. 2 is a time chart for explaining the operation of the control unit shown in FIG. 1... Schmitt trigger circuit, 2... Correction unit, 3... Counter unit, 4... Frequency divider (1/N
), 5...buffer, 6...control unit, 7...
・N bit shift register unit, 8... Bar display section, 9... N division correction coefficient deviation selection unit, 10.
...Arithmetic unit, 11...Setting unit, 12...
・Addition and subtraction unit. Patent applicant Oval Equipment Industry Co., Ltd. No. 1
Figure 2ffl

Claims (2)

[Claims] (1), the flow pulse transmitted at the maximum flow rate of the flowmeter is N
a control function that sets a bit capture time, stores and releases the flow rate pulse in a storage means such as an N-bit shift register, and an N-bit bar indicator that displays the flow rate pulse stored in the storage means; In the flow rate range of the flowmeter above,
A correction coefficient deviation device that stores non-linear deviation from a reference value in correspondence with each bit, a reference value setter that sets the reference value, an adder/subtractor that adds or subtracts the reference value and the non-linear deviation, and the adder/subtractor. and a correction means for correcting the flow rate pulse based on the result of the coefficient setting device. (2) The coefficient setter according to claim 1, further comprising conversion means for converting the non-linear deviation and the reference value into the same unit.