JP2644044B2 - Correlation type flow meter - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a correlation type flow meter which detects flow information at a plurality of locations in a flow path and measures a flow rate from a cross-correlation value thereof.

[Prior Art] Conventionally known correlation type flow meters include, for example, Japanese Patent Application No. 62-1047 (Japanese Patent Application Laid-Open No.
As shown in No. 79219), sensors are cut at a plurality of points spaced in the direction of flow to measure information about the flow, such as the propagation characteristics of ultrasonic waves or the capacitance of fluid. From the correlation of the measurement data of each of these sensors, a method is employed in which a time difference in which “turbulence of the fluid” generated in the fluid is detected by each sensor is calculated, and the flow rate is calculated based on the flow velocity data obtained from the time difference. I have.

For example, when two sensors are provided on the upstream side and the downstream side, flow information obtained from these sensors is
When these functions are represented by time functions of (t) and g (t), these functions are waveforms having substantially the same waveform and having a phase difference of τ, and between these functions, τ is a variable. A cross-correlation holds.

Therefore, an equation obtained by integrating the product of the function f (t) and g (t−τ) in a fixed section [0, T] By obtaining τ when becomes maximum, the flow velocity and the flow rate can be known from τ.

"Problem to be Solved by the Invention" By the way, the above-mentioned formula (I) expresses the functions f (t) and g
When the absolute value of (t) is large, the peak value takes a maximum value. Therefore, a peak value irrelevant to a peak related to the correlation calculation (due to turbulence of flow) due to external noise or the like is applied to one of the sensors. If detected, an erroneous correlation value may be calculated.

The present invention has been made in view of the above circumstances, and has as its object to eliminate the influence of a peak value that causes an error in a correlation operation.

Means for Solving the Problems In order to achieve the above object, the present invention provides a sensor that outputs a detection signal corresponding to a change in flow at a plurality of locations spaced apart from each other in a flow direction of a fluid. A correlation means for measuring the flow rate of the fluid from the cross-correlation calculation value of the detection signal of each sensor, a storage means for sequentially storing data of the calculated cross-correlation calculation values in time series, Comparing means for comparing a reference value set based on the time-series correlation operation value stored in the means with a newly supplied correlation operation value, and a correlation operation value determined to be out of reference by the comparison means And invalidation processing means for invalidating.

[Operation] With the above configuration, when a peak value irrelevant to the turbulence of the flow to be correlated is erroneously correlated, the resulting data is obtained from the data measured so far. It becomes a value outside the reference value, and the comparison means determines that, and as a result, is invalidated.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment in which the present invention is applied to an ultrasonic flowmeter. In FIG. 1, reference numeral 10 denotes a pipe for measuring a flow rate.

An upstream sensor 11 is provided on the upstream side (left side in the figure) of the outer periphery of the pipe 10, and on the downstream side (right side in the figure), an interval is provided in the pipe axis direction from the upstream sensor 11. In addition, a downstream sensor 12 is provided. The upstream sensor 11 and the downstream sensor 12 have the same configuration as each other, and are arranged in the pipe 10 and emit a ultrasonic wave transmitted by the transmitter 11a.
12b and a receiver 11 that is provided at a position facing the transmitters 11a and 12a with the pipe 10 interposed therebetween and receives an ultrasonic signal.
b and 12b.

The transmitters 11a and 12a of the sensors 11 and 12 have an ultrasonic source.
13 is connected, ultrasonic waves are transmitted from each of the transmitters 11a and 12a by a drive signal output from the ultrasonic source 13, and the ultrasonic waves are received by the receivers 11b and 12b across the pipeline. And converted into an electric signal.

Further, demodulators 14a and 14b are connected to the receivers 11b and 12b, respectively, so that electric signals from the receivers 11b and 12b are input to the demodulators 14a and 14b. And
When a disturbance occurs in the flow of the fluid in the pipe 10 and the input signal is modulated, a signal corresponding to the disturbance is transmitted to the demodulators 14a and 14a.
Output from 4b.

Furthermore, the turbulence signals output from the demodulators 14a and 14b are input to signal recorders 15a and 15b, and these signal recorders 15a and 15b convert the input signals from the demodulators 14a and 14b into A / D signals.
After the conversion, the data is temporarily stored in a built-in memory. The functions of the signal recorders 15a and 15b are controlled by the memory controllers 16a and 16b, and the data are supplied to the correlator 17 under the control of control signals supplied from the memory controllers 16a and 16b. It is supposed to.

The correlator 17 performs a cross-correlation calculation on the turbulence signal data D ₁ and D ₂ supplied from the signal recorders 15 a and 15 b based on the equation (1), and calculates the turbulence of the flow between the two sensors 11 and 12. and outputs to the control arithmetic unit 18 a time delay τ as the measurement result data S _1.

The control arithmetic unit 18, the measurement results and the ability to determine the correctness of the data S _1, a function of storing the measurement result data S ₁ for the past several times as a reference for this determination, measurement result data judged to be correct a function to calculate the flow rate output as flow data S ₂ regular according S _1, and the function of storing the number of occurrences of error data. Also the measurement data storage area of the control arithmetic unit 18, the measurement result data S ₁ over a predetermined time (predetermined number of sampling times) is chronologically stored,
These data are sequentially written and read in accordance with a first-in first-out principle, and are updated.

Hereinafter, explaining the contents of determination processing of the measurement result data S ₁ by the control arithmetic unit 18.

STEP1: Signal recorder 15 by memory controllers 16a and 16b
a.15b is controlled, and the flow disturbance signals D ₁ and D ₂ are read out,
Supply to correlator 17.

STEP2: A time τ is obtained by performing a cross-correlation operation on the turbulence signals D ₁ and D ₂ .

STEP3: Multiple measurement result data S ₁ stored in the storage area
Calculate the standard deviation of

STEP4: The calculated standard deviation is compared with a preset reference value. If the standard deviation is out of the reference value, the process proceeds to STEP5 and below. If the standard deviation is within the reference value, the process proceeds to STEP9 and below.

STEP5: calculating an average value of data S ₁ in the storage area.

STEP6: If the difference between the calculated average value and the measured data S ₁ is judged whether it is within the reference value, it is within the reference value STEP7
If the value is outside the reference value, the process proceeds to STEP 13 described later.

STEP7: The time-series data in the storage area is sequentially shifted, and the data is newly written. Further, the count value E of the counter that stores the number of occurrences of the error gater is reset.

STEP 8: The measured data S ₁ in terms of flow rate, and outputs it as a flow value.

On the other hand, if it is determined in STEP 4 that the standard deviation value is larger than the reference, it means that the measurement data has changed, and the processing of STEP 9 and the subsequent steps is performed on the degree of the change.

STEP 9: Measure the state of change of the measurement data in the storage area. That calculates the change rate of the measurement data S _1.

STEP10: Judge whether it is gradually increasing or gradually decreasing, and if any of them is applicable, STEP
Go to 11; if none of the above, go to STEP13.

STEP 11: Calculate the amount of change in the measurement data S1 stored in the storage area.

STEP 12: the calculated amount of change, to compare the variation between the measured data S ₁ of this and the previous, in the case of a difference between a predetermined reference captures a valid measurement data the
Proceed to STEP7, and if it is outside the prescribed standard,
Proceed to STEP 13 to process as a measurement error.

That is, in the above-described STEP 6 or STEP 12, when the measured data is out of the standard of the predetermined variation or the change rate, the following steps are performed for the measurement of such data.

STEP13: Count up the error counter in the control arithmetic circuit 18.

STEP14: Compare the count value E with the reference value N. If the number of errors is less than the reference value, return to STEP1 to repeat the measurement and calculation, and if it exceeds the reference value, proceed to STEP15.

STEP 15: the abnormality by continuous detection of the data, since the subsequent state not output the normal flow data S _2, causes abnormal data is measured, for example, failure of the flow meter itself, or the disturbance factor to the flow meter Activate alarms, etc. to encourage inquiries.

Through the above steps, even when a specific correlation operation value occurs due to the influence of noise or the like, an accurate flow rate is calculated without reflecting this data in the flow rate measurement data.

Further, in the case of the embodiment, a Japanese Patent Application No.
As disclosed in Japanese Patent Application Laid-Open No. 62-10447 as an embodiment, a control arithmetic unit is used to reduce the arithmetic load and eliminate the influence of noise.
18 correlator 17 and to the memory controller 16a · 16b control signals C ₁ -C ₃ was supplied from, to limit the delivery of the flow of data to the control computation unit 18 based on the control signal C ₁ -C ₃ It has become.

That is, the control calculator 18 refers to the past flow rate data S2 stored therein, that is, the change amount corresponding to the flow change, and calculates the expected value τ ′ of the time delay of the flow between the two sensors 11 and 12. Calculate. The setting of the predicted value is arbitrary, but, for example, the average value of the past flow rate data S2 or the flow rate data sampled last time and _two times before is used. The correlator is configured to perform a cross-correlation calculation within a range of [τ ′ ± Δτ] which is a time delay having a predetermined width Δτ before and after the set expected value τ ′ of the time delay. 17 and memory controllers 16a and 16b
The control signal C ₁ -C ₃ are supplied to the.

In the above embodiment, two sensors for measuring the turbulence of the flow are provided. However, more sensors may be provided. Also, as for the sensor, it goes without saying that not only an ultrasonic sensor but also other types of sensors such as a capacitance type may be used in the embodiment.

[Effects of the Invention] As is clear from the above description, according to the present invention, when performing a correlation operation based on a phase difference of a turbulence generated in a flow, a reference value based on time-series data of a past operation result and a new reference value are calculated. When the flow rate is out of the standard, the flow rate calculation value based on the calculation result is invalidated. This has the effect of preventing erroneous measurement due to the detected value and increasing the reliability of the flow meter.

[Brief description of the drawings]

1 shows an embodiment of the present invention. FIG. 1 is an overall block diagram, and FIG. 2 is a flowchart showing the processing contents of a control arithmetic unit. 10 ... Piping, 11 ... Upstream sensor (sensor), 12 ... Downstream sensor (sensor), 18 ... Control arithmetic unit.

Claims (1)

(57) [Claims] A sensor for outputting a detection signal corresponding to a change in flow is provided at a plurality of positions spaced from each other in a flow direction of a fluid, and the fluid is calculated from a cross-correlation calculation value of the detection signal of each sensor. In the correlation type flow meter for measuring the flow rate, a storage means for sequentially storing the data of the calculated cross-correlation calculation values in time series, and setting based on the time-series correlation calculation values stored in the storage means Comparing means for comparing the calculated reference value with the newly calculated correlation operation value, and invalidation processing means for invalidating the correlation operation value determined to be out of the reference value by the comparison means. Correlation type flow meter.