JPH102823A - Differential pressure measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the load on a host device by determining the variation of a detected differential pressure signal from the differential pressure signal of one sampling period before, performing a primary delay operation to the variation, and outputting the resulting value as a rocking signal. SOLUTION: A differential pressure detecting part 1 measures the pressure to be measured as discrete value, and outputs a differential pressure signal to a signal shaping part 2 and a differential pressure absolute value converting part 21 every prescribed sampling period. The signal noise-removed and shaped by the shaping part 2 is outputted from a signal converting part 3. The converting part 21 determines the difference of the differential pressure signal from the differential pressure signal of one sampling period before, converts the differential value to an absolute value, and outputs it to a digital primary delay filter 22. The filter 22 reads the time constant held in a memory 23 in order to determine the average value of the differential absolute value and smoothes the differential absolute value. A rocking signal converting part 24 converts the magnitude of the differential absolute value to a prescribed output signal, and outputs it as rocking signal. Thus, the load on a host computer side can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for calculating a swing signal on a differential pressure measuring device, which is capable of easily calculating a swing signal. The present invention relates to a differential pressure measuring device capable of outputting only necessary arranged swing information to a host device.

[0002]

2. Description of the Related Art FIG. 2 is a diagram illustrating the configuration of a conventional example generally used in the prior art. For example, "Yokogawa Technical Report" Vol.
No.1 (Vol.167) P25 Figure 8 Published by Yokogawa Electric Corporation
Issued January 20, 1992. In the figure, reference numeral 1 denotes a differential pressure detecting unit that measures a differential pressure of a measurement target at a certain sampling cycle and outputs differential pressure value data.

[0005] Reference numeral 2 denotes a signal shaping unit for shaping the waveform of the output signal of the differential pressure detecting unit 1. Reference numeral 3 denotes a signal conversion unit that converts an output signal from the signal shaping unit 2 so as to correspond to a predetermined span width, for example, a 4 to 20 mA span width, and outputs the converted signal.

In the above configuration, the measured differential pressure Pm is detected by the differential pressure detecting section 1, and an electric signal output I _out corresponding to the measured differential pressure Pm is output from the signal converting section 3.

[0005]

The differential pressure measuring device is mainly used together with an orifice to be used as a flow meter for measuring a flow rate of a fluid flowing in a pipe. The pressure difference generated before and after the orifice installed in the pipe is transmitted to and measured by a differential pressure measuring device via a pressure guiding tube.

The troubles that occur here include clogging of the pressure guiding tube. When the pressure guiding tube is clogged, the pressure in the piping is not correctly transmitted to the differential pressure measuring device, and an erroneous pressure signal is output.

[0007] At present, maintenance workers are regularly on-site,
The clogging is presumed from checking the clogging and the operator's instructions of the differential pressure measuring device output to the monitor of the control computer or the recorder from the normal.

However, in such a method, there is a possibility that a man-hour for inspection is generated, and the detection of the clogging is inaccurate because the judgment of the occurrence of the clogging is different for each person, and an appropriate measure is delayed.

By the way, as shown in FIG. 3, the pressure measured by the differential pressure measuring device is not always constant, but always includes a swing component. Until now, this oscillating component was unnecessary as a signal for plant control, and has been removed as noise in the differential pressure measuring device or the control computer.

However, as shown in FIG. 4, when the pressure guiding tube is clogged, the oscillating component is reduced, and when the pressure guiding tube is completely clogged, the oscillating component is eliminated and the pressure value becomes constant. From this, it is possible to predict the occurrence of clogging by using this swing component to quantitatively grasp the change in the swing component. Thus, the state of the plant can be known by using the swing component included in the signal, which has not been used until now.

Now, the measured pressure value P (t) is a discrete value that is updated at regular intervals. In calculating the magnitude of oscillation, the current pressure value P (t) and the immediately preceding measured value P (t-1)
The difference dP (t) is calculated. dP (t) = P (t)-P (t-1)

If the swing is large, the value of dP (t) becomes large. However, since this value greatly changes every time, it cannot be used as a clogging detection parameter as it is. It needs to be smoothed in some way.
Therefore, the average value of dP (t) within a certain time is defined as the magnitude X (t) of the swing component.

In this case, as shown in FIG. 5, in calculating the moving average, memory areas are required for the number of measured values for calculating the average value. If the number of measured values is n = 20, this requires one memory area for calculating the measured values, so that 21 memory areas are required.

[0014] FIG. 5, and read the new measured value at time t, discarding the oldest measurement values held in the memory Me A _b
Then, the new measured value is stored in the memory Me. This means that the contents of all memories are added, divided by the total number of memories, and an average value is obtained. In addition, when calculating the average value, it is necessary to add up the number of measured values and divide the result by the number. X (t) = (dP (tn) + dP (t-n + 1) + ・ ・ ・ + dP (t-1) + d
P (t)} / (n + 1)

Since such a complicated calculation is required,
The data cannot be processed unless the data of the measurement value relating to the swing is sent to a host computer and calculated. .

However, in such a device, in addition to the differential pressure measurement signal, all of the measured values relating to fluctuations are sent from the differential pressure measuring device to the host computer due to the limitation of the communication capability such as the communication speed. Have difficulty. It is not necessary that the measurement value relating to the swing is continuous data as compared with the measurement signal of the differential pressure, and it is considered that intermittent data to some extent is sufficient as diagnostic information.

Therefore, it is required that the processing of the oscillating component be processed on the differential pressure measuring device side so that information necessary for diagnosis can be appropriately obtained.

The present invention solves these problems. SUMMARY OF THE INVENTION An object of the present invention is to arrange a calculation process of a swing signal so as to be easily processable, to enable a calculation process of a swing signal on a differential pressure measuring device side, and to organize the necessary process for diagnosis of the device. It is an object of the present invention to provide a differential pressure measuring device capable of outputting only swing information to a host device.

[0019]

In order to achieve the above object, the present invention provides a differential pressure detecting section for detecting a differential pressure at a predetermined sampling period and outputting a differential pressure signal; Differential pressure measurement, comprising: a signal shaping section for removing a swing component from the differential pressure signal detected in step (a); and a differential pressure signal converting section for converting the differential pressure signal shaped by the signal shaping section into a predetermined output signal. In the apparatus, a difference absolute value calculation unit for calculating an amount of change between the differential pressure signal detected by the differential pressure detection unit and the differential pressure signal detected one sampling cycle before, and a first-order lag calculation for the amount of change And a first-order lag calculating section for outputting the calculated value as a swing signal.

[0020]

In the above configuration, for example, the differential pressure detecting section
Using a semiconductor pressure sensor and a CPU, the pressure of a measurement target is measured as a discrete value, and is output at predetermined sampling intervals.

The differential pressure signal output from the differential pressure detecting section is output to a signal shaping section and a differential absolute value converting section. The signal value output to the signal shaping unit is shaped to remove noise, and is output from the signal conversion unit as a differential pressure signal.

On the other hand, a difference between the differential pressure signal output to the differential absolute value converter and the previous differential pressure signal output one sampling cycle before is calculated by the differential absolute value converter.
The difference value is converted to an absolute value and output to a digital first-order lag filter.

The digital first-order lag filter reads the time constant stored in the memory and smoothes the absolute value of the difference with the digital first-order lag filter in order to obtain an average value of the difference absolute value.

The swing signal converter converts the magnitude of the smoothed absolute difference value output from the digital first-order lag filter into a predetermined output signal, and outputs the output signal as a swing signal. Hereinafter, a detailed description will be given based on embodiments.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of a main part of an embodiment of the present invention. In the figure, the configuration of the same symbol as FIG. 2 represents the same function. Hereinafter, only differences from FIG. 2 will be described.

Numeral 21 denotes a difference absolute value converter for taking the difference between the differential pressure signal output from the differential pressure detector 1 and the differential pressure signal output immediately before, and converting the difference into an absolute value. . 22
Is a digital first-order lag filter that makes the difference absolute value a stable value. 23 is a digital first-order lag filter 22
This is a memory for storing a settable time constant used in.

The magnitude of the swing component included in the differential pressure signal is calculated by the absolute difference converter 21 and the digital first-order lag filter 22. Reference numeral 24 denotes an oscillating signal converter that converts the smoothed absolute difference value output from the digital first-order lag filter 22 into a predetermined signal, for example, a digital signal, as an oscillating signal.

In the above configuration, the differential pressure detecting section 1 measures the pressure of the object to be measured as a discrete value by using, for example, a semiconductor pressure sensor and a CPU, and outputs it at predetermined sampling intervals.

The differential pressure signal output from the differential pressure detector 1 is
The signal is output to the signal shaping unit 2 and the absolute difference conversion unit 21.
The signal value output to the signal shaping unit 2 is subjected to signal shaping to remove noise, and as a differential pressure signal similar to the conventional example in FIG.
The signal is output from the signal converter 3.

On the other hand, a difference between the differential pressure signal output to the differential absolute value converter 21 and the immediately preceding differential pressure signal output one sampling cycle before is calculated in the differential absolute value converter 21. The difference value is converted into an absolute value and output to the digital first-order lag filter 22.

The digital first-order lag filter 22 reads the time constant held in the memory 23 in order to obtain an average value of the absolute value of the difference.
2, the absolute difference value is smoothed.

[0032] In the oscillating signal converter 24, is outputted from the digital first-order lag filter 22, the magnitude of the smoothed difference absolute value is converted into a predetermined output signal is output as oscillating signal I _a.

Thus, the measured pressure value P (t)
Is a discrete value that is updated every fixed time. In calculating the magnitude of the swing, the difference dP between the current pressure value P (t) and the immediately preceding measured value P (t-1) is calculated by the difference absolute value converter 21.
Calculate (t). dP (t) = P (t)-P (t-1)

If the swing is large, the value of dP (t) becomes large. However, since this value greatly changes every time, it cannot be used as a clogging detection parameter as it is. It needs to be smoothed in some way.

In the present invention, a first-order lag filter 22 is used as a method of the smoothing processing. Swing component X (t)
X (t) = X (t-1) + K {dP (t)-X (t-1)} K = 1 -exp (-Ts / T) Ts: Output period of discrete values T: Time constant Becomes

As a result, the variables to be stored are X (t-1) and
Only K is required, and the computational power required for the calculation may be very small. Therefore, even in the case of a general differential pressure measuring device in which only a CPU or the like having a small processing capacity is mounted, the calculation process becomes possible, and the differential pressure measuring device can process the swing signal calculation process. Thus, the burden on the upper computer can be reduced.

In the method using the moving average as in the conventional example shown in FIG. 2, the degree of smoothing is determined by the number of measured values used for calculating the average value.
In the method using 2, the value can be easily changed by changing the value of K. Therefore, it is possible to flexibly respond to the object for which the swing is calculated. As described above, the method of the present invention is advantageous in all respects of calculation processing and memory area.

[0038]

As described above in detail, in the present invention, the first-order lag filter 22 is used as a method of smoothing the swing signal. As a result, the number of variables to be stored may be small, and the calculation capability required for the calculation may be very small.

Therefore, even in a general differential pressure measuring device in which only a CPU or the like having a small calculation processing capacity is mounted, the calculation process can be performed, and the calculation process of the swing signal is performed by the differential pressure measuring device side. And the burden on the host computer can be reduced.

In the method using the moving average as in the conventional example, the degree of smoothing is determined by the number of measured values used for calculating the average value. However, in the method using the first-order lag filter as in the present invention, It can be easily changed by changing the value of the constant. Therefore, it is possible to flexibly respond to the object for which the swing is calculated.

As described above, the method of the present invention employs calculation processing,
This is advantageous over the entire memory area.

Therefore, the swing signal calculation processing is configured to be easily processable, and the swing signal calculation processing on the differential pressure measuring device side is enabled, so that the sorted swing necessary for the diagnosis of the device is obtained. A differential pressure measuring device capable of outputting only dynamic information to a host device can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a main part configuration of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a configuration of a conventional example generally used in the related art.

FIG. 3 is an operation explanatory diagram of FIG. 2;

FIG. 4 is an operation explanatory diagram of FIG. 2;

FIG. 5 is an operation explanatory diagram of FIG. 2;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 differential pressure detecting section 2 signal shaping section 3 signal converting section 21 absolute difference value converting section 22 digital first order lag filter 23 memory 24 swing signal converting section

Claims (1)

[Claims] 1. A differential pressure detecting section for detecting a differential pressure at every predetermined sampling period and outputting a differential pressure signal, and a signal shaping for removing a swing component from the differential pressure signal detected by the differential pressure detecting section. Unit, and a differential pressure measuring device comprising a differential pressure signal converting unit for converting the differential pressure signal shaped by the signal shaping unit to a predetermined output signal, wherein the differential pressure signal detected by the differential pressure detecting unit is A difference absolute value calculation unit for calculating a change amount from a differential pressure signal detected one sampling period before; a first order delay calculation unit for performing a first order delay operation on the change amount and outputting the operation value as a swing signal A differential pressure measuring device comprising: