JPH0257918A - Electromagnetic flowmeter - Google Patents

Abstract

PURPOSE:To eliminate waste of an arithmetic processing and to shorten a time for execution by providing noise removal processing means in an arithmetic control element and by operating selectively only the noise removal processing means corresponding to noise identified by an identifying means. CONSTITUTION:When an arithmetic instruction is inputted from a communicator 17, an arithmetic control element 9 turns switches 5, 6 ON/OFF to make positive, zero and negative exciting currents flow through an exciting coil 3, takes in a signal voltage e0 at each timing, computes a flow rate signal and outputs it to the communicator 17, while displaying the same in a display element 18. Next, it is judged whether a noise component contained in the flow rate signal is larger than a prescribed level or not. When it is larger, the kind of the noise is identified and the result of identification is displayed in the display element 18. When an instruction key for removal of the noise of the kind identified is operated, the instruction is transmitted to the control element 9, and in the control element 9, a flow rate signal wherefrom the noise component corresponding to said instruction is removed is outputted and trend-displayed in the display element 18.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to an electromagnetic flowmeter, and particularly to an electromagnetic flowmeter having a noise removal processing function.

(b) Conventional technology In general, an electromagnetic flowmeter consists of a conduit through which a fluid to be measured flows, a pair of electrodes exposed within the conduit and arranged facing each other, and a pair of electrodes arranged facing each other in the axial direction of the conduit and in the direction in which the positive electrode is arranged. The apparatus includes excitation means for applying a magnetic field in orthogonal directions, and circuit means for outputting an electric signal depending on the fluid flow type obtained between the electrodes. In this type of electromagnetic flowmeter, signals proportional to fluid flow rate include electromagnetic induction noise voltage generated due to temporal changes in excitation magnetic flux density, commercial frequency noise voltage caused by commercial power supply, and electrode It contains several superimposed electrochemical noise voltages that occur electrochemically between fluids and low-frequency random noises (flow noise) that increase with flow velocity that occur in slurry fluids and fluids with low conductivity. It is normal that Conventional electromagnetic flowmeters are equipped with hardware or software noise removal processing functions to remove these noises.

(c) Problems to be Solved by the Invention An electromagnetic flowmeter that is equipped with only a means for removing specific noises among the various noises described above cannot cope with the occurrence of other noises. However, if you try to remove noise by using only hardware circuits, only software, or a combination of hardware and software in order to deal with all of the various types of noise mentioned above, the circuit will become complicated and the calculation processing time will be longer when using software. There are problems such as increased costs and higher costs.

The present invention has been made in view of the above-mentioned problems, and aims to provide an electromagnetic flowmeter that can cope with various types of noise, has a quick response, and has excellent cost performance.

(d) Means and operation for solving the problems This electromagnetic flowmeter consists of a conduit whose inner surface is insulated and through which the fluid to be measured flows, and a pair of conduits exposed inside the conduit and placed facing each other. an electrode, excitation means for applying a magnetic field in a direction orthogonal to the axial direction of the conduit and the arrangement direction of the electrodes, a circuit means for outputting an electric signal according to a fluid flow rate between the electrodes, and an output of the circuit means. an arithmetic control unit that converts and takes in a digital signal, performs digital arithmetic operations, converts the output signal into an analog signal, and outputs the output signal; and a communicator that instructs the arithmetic control unit to perform arithmetic control contents, the communicator comprising: A display means for displaying a trend of the output data from the arithmetic control section; and an identification means for identifying the type of generated noise based on the trend display data; The noise removal processing means is provided, and only the noise removal processing means corresponding to the noise identified by the identification means is selectively operated.

In this electromagnetic flowmeter, the output signal of the noise removal process from the arithmetic control section is displayed as a trend on the display means of the communicator. By looking at this trend display data or by automatically processing the trend display data, it is possible to identify which type of noise is larger. The identified content is transmitted to the arithmetic control section, and the arithmetic control section operates only the corresponding noise removal means. Thereafter, the arithmetic control section outputs a signal from which the identified noise has been removed. It is not necessary to identify only one type of noise, and two or more types of noise may be identified. It is rare for all noises that actually appear to have the same effect, so it is sufficient to select one or several noise types based on the noise and operate the corresponding noise removal processing means.

(E) Examples The present invention will be explained in more detail with reference to Examples below.

FIG. 1 is a block diagram of an electromagnetic flowmeter showing an embodiment of the present invention. In the figure, a pair of electrodes 2a and 2b are provided inside a conduit 1, and a magnetic field is applied to the outside of the conduit 1 in a direction perpendicular to the axial direction of the conduit 1 and the arrangement direction of the electrodes 2a and 2b. An excitation coil 3 is provided to apply .

A switch 5.6 for polarity switching is connected between the excitation coil 3 and the constant current power supply 4, and by turning on/off the changeover switch 5.6, the excitation coil 3 can be set to positive, 0, or negative excitation. Current flows alternately.

When fluid flows through the conduit l and a voltage e0 is induced between the electrodes 2a and 2b, this voltage e0 is amplified by the preamplifier 7 and converted into a digital signal by the A/D converter 8. The signal is input to an arithmetic control section (microcomputer) 9. The arithmetic control unit 9 includes CPUIOROMII, R
AM12, input/output interface 13, D/A converter 1
4 and a communication interface 15, it performs calculations on the digital signal taken in from the A/D converter 8, converts the flow rate signal into an analog signal with the D/A converter 14, and sends it to the receiver 16. It will be done. The output of the D/A converter 14 and the communication interface 15 are connected in parallel, and a communicator 17 is connected to these. Input/output interface 1
3, timing signals P, , P, , P, shown in FIG. 2 are output in response to a command from CPU10. The switch 5 is turned on by the timing signal P, and the timing signal P2
The switch 6 is turned on, and the induced voltage e0 is sampled using the timing signal P3.

In addition to the function of calculating the flow rate signal, the calculation control unit 9 has a function of removing sudden noise (slurry noise), a function of removing electrochemical noise, a function of removing commercial frequency noise, and a function of removing flow noise. It has a function to remove magnetic flux differential noise and a function to remove magnetic flux differential noise.

Sudden noise (slurry noise) is caused by slurry fluid, etc.
When slurry such as pebbles, sand, or pulp chips contained in the fluid collides with the electrode, the electrical equilibrium at the interface between the electrode and the fluid is temporarily broken, causing an instantaneous voltage of several mV to several hundred mV between the electrodes. This generates a voltage of .

This causes a whisker-like signal to appear in the output.

Countermeasures for removal include binary excitation, moving average, increasing the damping time constant, and adding a rate limit function, any of which should be adopted.

The rate limit function constantly monitors changes in measured values,
If the measured value suddenly changes, and the sudden amount is larger than a preset value, the output is held at the previous measured value for a certain period of time, and the measured value still changes even after that period. Only when the hold is held is released and the measured value is output to the outside.

Electrochemical noise can cause changes in fluid pH and conductivity upstream of electromagnetic flowmeters.
It is caused by a change in the potential of the electrodes relative to the fluid, which causes a gradual change in the voltage between the electrodes.

For example, in the case of three-value excitation, each sampling data of positive direction excitation, de-excitation, negative direction excitation, and de-excitation is El,
When E2, E3, and E4 are used, the measured value E can be removed by performing calculations such as Eo = E1 + 3E2 3E3 + E4.

Note that this calculation formula can also remove commercial frequency noise and magnetic flux differential noise, which will be described later, in addition to electrochemical noise.

Commercial frequency noise is superimposed on signals due to common potential, induction, etc. If the sampling period is an exact integer multiple of the commercial frequency, or is completely synchronized with the commercial frequency, and the above calculation is performed, it will be removed, but if the sampling period is not completely synchronized with the commercial frequency, the deviation will be removed. appears in the output as a beat. As a result, the output changes gradually.

Flow noise occurs particularly when the conductivity of the fluid is low or when the flow rate is relatively high. From several Hz @I OHz
Since the output has a relatively high frequency component, the output exhibits random hunting. Eliminate it by increasing the moving average, increasing the excitation frequency, and increasing the damping time constant.

Magnetic flux differential noise appears as a so-called differential waveform in response to changes in magnetic flux at the start and end of excitation. If the time from excitation switching to sampling is constant, the magnitude for each sampling is the same, but the polarity is the same as the direction in which the magnetic field changes. In the case of three-value excitation, it can be removed by executing the above-mentioned calculation.

The communicator 17 includes a display section 18 and a key input section 19. The display section 18 displays the output data from the calculation control section 9 as a trend.

The key power section 19 includes keys for giving calculation commands to the calculation control section 9, keys for instructing removal processing of the above-mentioned various noises, and the like. In addition, the communicator 17 is
It is equipped with a machine Nr that identifies the type of noise based on the data displayed as a trend.

Next, the overall operation of the electromagnetic current meter needle of the above embodiment will be explained with reference to the flowchart shown in FIG.

First, the communicator 17 is connected to the output line of the electromagnetic flowmeter body, that is, the output line of the arithmetic and control section 9 (step 5TI). Then, a calculation command is inputted from the communicator 17 to the calculation control unit 9, and the calculation control unit 9 turns on/off the switch 5.6 to cause positive, zero, and negative excitation currents to flow through the excitation coil 3. Signal voltage e0 at timing
The flow rate signal is calculated and output to the communicator 17. The communicator 17 displays this output data as a trend on the display unit 18 (step 5T2).

Next, it is determined whether the noise component included in the flow rate signal is higher than a predetermined level (step 5T3), and if it is, it is determined what type of noise the noise is (step 5T4), and the identified result is is displayed on the display section 18. When the operator sees this display and operates the identified type of noise removal command key, the command is transmitted to the calculation control section 9 (step 5T5). Arithmetic control unit 9
selects and operates only the corresponding noise removal processing routine in response to this command. Therefore, the flow rate signal from which the noise has been removed is output from the calculation control unit 9, and the trend is displayed on the display unit 18 of the communicator I7 (
Step 5T6).

In the above embodiment, the identification of noise in the communicator 17 is automatically processed by the communicator 17, but the operator visually observes the trend display of the flow rate signal containing noise and determines what kind of noise is included. may be identified.

In addition, in the identification process, if multiple types of noise causes correspond, the arithmetic control unit 9 executes composite noise processing by commanding each from the communicator 17.

Further, the arithmetic control section 9 calculates the standard deviation and average value of the sampling data, displays these standard deviations and average values on the trend display screen of the display section 18 of the communicator 17, and sets the values to predetermined settings. It may be used to compare the values and determine whether noise processing is necessary.

(f) Effects of the Invention According to the present invention, the communicator is provided with a display means for displaying a trend of output data from the arithmetic control section, and an identification means for identifying the type of generated noise based on the trend display data. , since the arithmetic control unit is equipped with separate noise removal processing means for multiple types of noise, and only the noise removal means corresponding to the noise identified by the identification means is selectively operated, other unnecessary noise removal processing is performed. It is possible to obtain an electromagnetic flow π needle with a short execution time without operating the processing means, eliminating wasteful calculation processing. Furthermore, since noise identification is performed on the communicator, it does not affect the actual output signal of the electromagnetic flowmeter. On top of that,
The output data before and after the noise removal process is displayed as a trend, so you can check the effectiveness of the noise removal process.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an electromagnetic flowmeter showing an embodiment of the present invention, Fig. 2 is a time chart showing timing signals of the electromagnetic flowmeter, and Fig. 3 shows the noise removal processing operation of the electromagnetic flowmeter. It is a flow diagram for explanation. ■ = conduit, 2a/2b: electrode, 3: excitation coil, 7: pre-amplifier, 8: A/D converter, 9:
Arithmetic control unit, 17: Communicator, 18: Display unit, 1
9: Key human resources department. Figure 2 Figure 3

Claims (1)

[Claims] (1) A conduit whose inner surface is insulated and through which the fluid to be measured flows; a pair of electrodes exposed within the conduit and arranged facing each other; excitation means for applying a magnetic field; circuit means for outputting an electric signal according to the fluid flow rate between the electrodes; the output of the circuit means is converted into a digital signal and taken in, digital calculation is performed, and the output signal is converted to analog. In the electromagnetic flowmeter, the electromagnetic flowmeter includes a calculation control unit that outputs the calculation control unit, and a communicator that commands the calculation control content to the calculation control unit, a display unit that displays a trend of output data from the calculation control unit on the communicator; an identification means for identifying the type of generated noise based on the trend display data, and the arithmetic control section includes separate noise removal processing means for a plurality of types of noise, and the noise identified by the identification means An electromagnetic flowmeter characterized in that only a noise removal processing means corresponding to the above is selectively operated.