JPH0353129A - Correlational flow meter - Google Patents

Abstract

PURPOSE:To calculate an accurate correlation value to prevent the error of flow rate measurement by subjecting detection signals of respective sensors and their inverted signals to cross-correlation operation. CONSTITUTION:A pipe 10 is provided with an upstream sensor 11 and a downstream sensor 12, and ultrasonic waves are transmitted from transmitters 11a and 12a and are received by receivers 11b and 12b. Reception signals are inputted to demodulators 14a and 14b, and signals corresponding to disturbance are outputted from demodulators to signal recorders 15a and 15b at the time of abnormality of input signals due to a turbulent flow of the fluid in the pipe 10 and are subjected to A/D conversion by recorders 15a and 15b and are not only temporarily stored as disturbance signal data D1 and D2 in an incorporated memory but also supplied to averaging devices 16a and 16b and a correlator 17. The correlator 17 performs the cross-correlation operation to obtain a correlation value Rj and uses numerical values obtained by inverting signals from sensors 11 and 12 to obtain a correlation value Sj, and a computing element 18 obtains a correlation value by a maximum value of the correlation value Rj+Sj. Thus, disturbance of the fluid is accurately recognized independently of absolute values of signals from sensors 11 and 12.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a correlation type flowmeter that detects flow information at multiple locations in a flow path and measures the flow rate from the cross-correlation values.

``Prior Art'' Conventionally known correlation type flowmeters are known to have rAI/; A sensor is installed at a location of several meters, and this sensor measures information related to the flow, such as the propagation characteristics of ultrasonic waves or the electrostatic capacity of the fluid. From the correlation of the measurement data of each sensor, the fluid The system calculates the time difference between when each sensor detects the "flow turbulence" that occurs, and calculates the flow rate using flow velocity data obtained from this time difference.

For example, if two sensors are installed on the upstream and downstream sides, the flow information obtained from these sensors is expressed as f(t
), g(t), these functions have almost identical waveforms with a phase difference of τ, and there is a cross-correlation between these functions with τ as a variable. A relationship is established.

Therefore, the formula R=I;Bt)・g(t−τ)d t , which integrates the product of the function f (t) and g(t−τ) over a certain interval [0, T]・
By determining τ when (1) is the maximum, the flow velocity and flow rate can be determined from this τ.

"Problem to be Solved by the Invention" By the way, the above equation (1) is the function f(t) and g(
If the absolute value of t) is large, it will take the maximum value, so for example, the above two functions will be shown in Figure 2 (a) and (b), respectively.
Assuming that it has the characteristics shown in , the parts with large absolute values (mountain parts) as shown by chain lines A and A'
Therefore, there is a problem in that it is impossible to detect true correlation values occurring in portions (valley portions) of small absolute values as shown by chain lines B and B'.

An object of the present invention is to eliminate the drawback of conventional correlation type flowmeters in that true correlation values cannot be detected, and to perform accurate correlation calculations based on more appropriate data.

"Means for Solving the Problems" In order to achieve the above object, the present invention provides a method in which sensors that output detection signals corresponding to changes in flow are arranged at multiple locations spaced apart from each other in the fluid flow direction. In the correlation type flowmeter, the flow flt of the fluid is measured by cross-correlating the detection signals of each sensor with a correlation power, and the correlator calculates the detection signals of each sensor and these detection signals. It is configured to perform a cross-correlation calculation with the inverted signal of .

"Operation" With the above configuration, correlation calculation can be performed based on changes due to either positive or negative disturbances in the detection signal, regardless of the magnitude of the absolute value of the detection signal supplied from each sensor.

"Example" Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

Figure 1 shows the application of the present invention to an ultrasonic flowmeter.
Reference numeral 10 in the figure is a pipe through which the flow rate is measured.

An upstream sensor 1l is provided on the upstream side (left side in the figure) of the outer periphery of the pipe 10, and an upstream sensor 1l is provided on the downstream side (right side in the figure) at an interval from the upstream sensor 1l in the pipe axis direction. A downstream sensor l2 is provided. The upstream sensor 11 and the downstream sensor l2 have the same configuration, and include transmitters 11a-l2a installed in the pipe 10 and transmitting ultrasonic waves, and It is comprised of receiving sections 1, 1, and 12b that are placed at opposite positions to receive ultrasonic signals.

Transmission from each of the sensors 11 and l2 W l 1 a and 12a
An ultrasonic source 13 is connected to the ultrasonic source 1.
Each transmitter 11a, 1
Ultrasonic waves are emitted from 2a, and the ultrasonic waves cross the pipe, are received by the receivers 1lb and 12b, and are converted into electrical signals.

Further, each of the receiving i11lb-12b has a demodulator 14a-
14b is connected so that electrical signals from the respective receivers 1lb and 12b are input to these demodulators 14a and 14b. When turbulence occurs in the flow of fluid in the pipe 10 and this input signal is modulated, the turbulence is dealt with. The signals are outputted from the demodulators 14a-14b.

Furthermore, the disturbance signals outputted from each fEJX'l2:+14a-14b are signal recording domains 15a and 15b.
These signal records 2315a and 15b are input to
The human input signals from fEl'lml4a and 14b are A/D converted, and are temporarily stored in a built-in memory, and the temporarily stored signals are used as disturbance signal data D1, D,
average? :4 1 6 a-1 6 b and correlation delay I7
It is designed to supply each.

In the correlation type flowmeter configured as described above, the correlator 17 performs the above-mentioned (1
) and outputs the result to the calculation glue 18 as a correlation result C.

In the correlator 17, the correlation calculation corresponding to the above-mentioned equation (1) is performed as R j =”X [X sX Y l+J
(However, X+, y+ generally indicate the signals sampled at the upstream and downstream sensors 1l and 12 at time i, and j indicates the phase difference when the correlation value is maximum. Also, x.yi are all D/ with n-pit configuration.
This is the number in the range O~2'' obtained from A converter.
Using the numerical value obtained by inverting the signals from both sensors 11 and l2 by the calculation, s j = 4 (2" - x .) x (2゜ Y I + J)
A similar correlation calculation is performed based on the formula, and these Rj
By calculating the sum of and Sj, the influence of the absolute value of the signal is eliminated. That is, the above Rj+
By the correlation calculation of Sj, it is possible to accurately distinguish disturbances occurring on either side of the peaks or valleys of the data obtained from both sensors 1 and 12 from other data.

The formula is obtained, and in this formula, 2 n "X x . is 2'(m+1) of the average value of
(however, this value varies depending on the value of j).

Therefore, in the correlation type flowmeter of the above embodiment, based on the above expansion formula, the correlation value Rj, the average value of the data obtained from the average 23 t e a · 16b, and the A/D conversion are calculated in the calculation mat 18. By processing the number n of pits constituting the device, a correlation calculation corresponding to [Rj+Sj] is performed using the detection signal itself and its inverted signal, and the absolute value of the measurement data obtained from the sensors 11 and 12 is calculated. influence has been eliminated. Note that it is of course possible to calculate [Rj+Sj] itself without using such an arithmetic expression.

Furthermore, in the above embodiment, the correlation value is calculated from the maximum value of [RJ+Sj], but the signal obtained from the sensor at time t and its inverted signal are compared, and the correlation value is determined by the signal with the larger change. The value Rj or Sj may be employed as the correlation value.

In the above embodiment, the sensors for measuring flow turbulence are provided at two locations, but the sensors may be provided at more locations. Further, as for the sensor, it is of course possible to use not only the ultrasonic sensor of the embodiment but also a sensor of other types such as a capacitance type.

"Effects of the Invention" As is clear from the above description, the present invention provides a current meter that measures flow rate by cross-correlation calculation based on information obtained from sensors provided on the upstream and downstream sides of the flow. Since the correlation calculation is performed using the signal itself obtained from the sensor and the inverted signal of this signal, flow disturbances can be accurately grasped regardless of the magnitude of the absolute value of the signal from the sensor. , it is possible to calculate an accurate correlation value and prevent flow measurement errors from occurring.

[Brief explanation of drawings]

FIG. 1 is a graph showing a correlation type current meter, and FIG. 2 is a graph showing examples of waveforms of detection signals from upstream and downstream sensors, respectively. 10. ．． ... Piping, 11 ... Upstream sensor, 12 ... ．． ．． Downstream sensor, 16a, 16b...
...Average 2asl7... Correlation domain, I8...
...Arithmetic unit.

Claims (1)

[Claims] Sensors that output detection signals corresponding to changes in the flow are arranged at multiple locations spaced apart from each other in the fluid flow direction, and a correlator calculates the cross-correlation of the detection signals of these sensors. 1. A correlation type flowmeter configured to measure a flow rate of the flow rate of the flow rate, wherein the correlator performs a cross-correlation calculation using the detection signals of each sensor and their inverted signals.