JPH0573165B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an electromagnetic flowmeter, and in particular to an electromagnetic flowmeter suitable for removing sudden changes in output caused by various sudden noises that surround conventional flow rate signal data. Regarding flowmeters.

[Conventional technology]

Generally, in an electromagnetic flowmeter, the following voltages are considered to occur between the electrodes of the detector.

(1) Signal voltage proportional to fluid flow velocity, (2) Magnetic induction noise voltage that occurs when the excitation current, that is, the polarity of the magnetic field changes over time, (3) Induction noise voltage that circulates from the commercial power supply, (4) ) DC noise voltage generated in the closed loop created via the measuring fluid and electrodes and the converter circuit, and these voltages are output in a combined form between the electrodes.

As an electromagnetic flowmeter, among the above four voltages,
It must be possible to separate only the signal voltage mentioned in (1) above.

Therefore, the above-mentioned
Time ts from the time when the voltage in (2) disappears until the excitation is cut off
to sample. Furthermore, when the sampling time ts is controlled in synchronization with the power supply, the voltage in (3) above is averaged and removed by integration processing. Further, in order to remove the voltage mentioned in (4) above, the microprocessor performs an integral value difference calculation according to the following equation.

{(Es+Eo+Eb)−Eb}+{(−1)(−Es+Eo−Eb)
−Eb}/2=Es……(1) where Es: Positive excitation flow signal voltage (current value) −Es: Negative excitation flow signal voltage (previous value) Eo: DC noise voltage (offset voltage) Eb: Bias voltage of D/A converter 13 Stable flow rate measurement is performed by the above-described noise removal processing (see Japanese Patent Laid-Open No. 158516/1983).

[Problem that the invention seeks to solve]

However, in equation (1) above, the signal data Es, -Es, and Eo obtained by synchronizing with the power supply, in other words, the current value and the previous value, may be affected by a momentary power failure (generally, the sampling time t becomes longer) or the power supply If an abnormal value is incorporated into one sampling data due to the introduction of sudden noise equivalent to a synchronization signal (generally, the sampling time t becomes shorter), it will affect the results of two calculations.

Therefore, in order to suppress output fluctuations caused by this sudden noise, the conventional technology has been designed to: 1) primary CR of the electrical circuit;
Processing by converting the filter to sampling calculation, 2) Smoothing as much as possible using moving average processing, 3)
Focusing on the fact that fluctuations in flow rate are gentle with respect to sampling time, we monitor the rate of change in sampling data and take actions such as forcibly cutting off part of the data when it exceeds a set value range. Ta. That is, in the above-mentioned sudden noise removal processes 1) to 3), discrimination between normal flow rate signal data and abnormal flow rate signal data was not clearly processed, and the process was simply to suppress fluctuations in output.

An object of the present invention is to provide an electromagnetic flowmeter that clearly discriminates between normal flow signal data and abnormal flow signal data and performs stable flow measurement.

[Means for solving problems]

In order to achieve such an objective, the present invention
The detector includes a conduit through which the fluid to be measured passes, an excitation coil that applies a magnetic field in the radial direction of the conduit, and a pair of electrodes provided on the conduit surface perpendicular to the direction of the magnetic field and the axial direction of the conduit. In an electromagnetic flowmeter that calculates the integral value difference of the signal obtained from the above and extracts it as a flow rate signal, an even number of at least 6 storage areas for the flow rate signals to be sequentially captured are provided, and the areas are arranged sequentially from the minimum value to the maximum value. The present invention is characterized in that it includes means for treating the average value of the two values placed at the center of the results as a flow rate signal.

[Effect]

In this way, when the suddenly changed flow rate data is taken into the storage area and rearranged from the minimum value to the maximum value, it will be arranged as the minimum value or maximum value, or as a value close to the minimum value or maximum value. Become. Therefore, since the two pieces of data placed in the center of the storage area cannot correspond to sudden changes, stable flow rate measurement can be performed.

〔Example〕

An embodiment of an electromagnetic flowmeter according to the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic configuration of the electromagnetic flowmeter. In the figure, 1 is an excitation coil attached to the detection pipe wall, 2 is an insulated conduit through which the measurement fluid passes, and 3
A and 3b are a pair of electrodes installed in the insulated conduit 2 for detecting a flow rate signal, and these constitute an electromagnetic flow rate detector. The excitation current a flowing through the excitation coil 1 is connected to the microprocessor 4.
, an excitation signal control circuit 5, and an excitation circuit 6. That is, the signals b and c from the microprocessor 4 are divided into a positive excitation signal d and a negative excitation signal e by the excitation signal control circuit 5, and the signals b and c from the excitation signal control circuit 5 are divided into a positive excitation signal d and a negative excitation signal e. An excitation current a having a waveform shown in FIG. 3 is supplied. As shown in FIG. 3, both the positive excitation current A and the negative excitation current B are on for a period of _t2 out of one measurement time T.
The remaining time _t1 is an excitation current suspension period. The flow rate signal generated in the electrodes 3a, 3b by the excitation current a is amplified by the preamplifier 7, as shown in FIG. 1, and becomes a signal having the waveform shown in FIG. 3(iv). ing. This signal is outputted from the preamplifier 7 as a positive flow rate signal or a negative flow rate signal depending on the polarity of the excitation currents A and B and the flow direction of the fluid. Therefore, the negative flow rate signal -Es shown in FIG.
Further, the positive flow rate signal Es is directly connected to the A/D converter 13. This operation is performed by controlling the semiconductor switches 9 and 10 with the measurement-calibration control signal f from the microprocessor 4, so that only positive voltage is input to the A/D converter 13. It's getting old.

The microprocessor 4 executes the processing (steps 20 to 100) shown in FIG. 2, which is preprogrammed in the storage device 15, every period T shown in FIG. 3(v), and also executes the processing shown in FIG. The hardware control process 200 synchronized with the power supply is controlled by the power supply synchronization signal shown in FIG. 3 (for example, 4→3→2→1→(0
= 4) → 3...) is counted and executed by interrupt processing. Further, the microprocessor 4 is adapted to output a normalized flow rate signal Io via a D/A converter 14 after performing flow rate calculations.

Here, if an instantaneous power outage occurs in the commercial frequency as shown in Figure 5, the interrupt signal shown in the figure is lost, and as a result, the time management control by power synchronization becomes abnormal as shown in Figure 5. Due to the sampling time t _s ⁺ _o shown in the figure, abnormal data is mixed into the flow rate signal data. When this abnormal data is mixed in, abnormal data removal processing is performed in steps 40 to 80 of the flowchart shown in FIG. In the flowchart of FIG. 2, after initialization is performed in step 10 from the start, a determination is made in step 10 to wait for a cycle. Next, in step 30, it is determined whether the data is a flow rate signal, and if it is a flow rate signal, the current flow rate data is set in step 40. Next, in step 50, the previous flow rate data is moved onto the memory. Furthermore, in step 60, the flow rate data are sequentially rearranged from the minimum value to the maximum value.

The operation on the memory in this case will be explained using FIG. 2 and 3. The memory used has, for example, six storage areas. In the figure, after setting the current flow rate signal data, discarding the oldest data among the previous flow rate signal data (symbol (a)), and setting the current flow rate signal data in six storage areas (symbol (b)) Rearrange data 1 to 6 in order from minimum value to maximum value. Furthermore, in step 70, the average value processing of flow rate data 3 and 4 (corresponding to the shaded area in FIG.
Then, the average value thus obtained is set in the flow rate calculation register (see (c) in FIG. 2).

Here, the memory has six storage areas as described above, and may have eight or ten storage areas, for example. However, if the storage area has four storage areas, the effects of the present invention cannot be obtained. The reason is that the flow rate data stored in the memory has been subjected to an integral difference calculation in order to remove the DC noise voltage described above. That is, before the integral value difference calculation, five signals are sent out in sequence, and the four values calculated in sequence, such as the first and second, the second and third, and the third and fourth, are It will be stored in the memory. However, if there is one abnormal data among the five signals, two difference calculation values including the abnormal data will be generated and stored in the memory as the minimum value or maximum value. In this case, the memory is arranged with two normal values placed adjacent to each other and two abnormal values placed adjacent to these normal value groups. Therefore, if one maximum value and one minimum value are removed and two pieces of flow rate data placed in the center are selected, one of them will become abnormal data.

From what has been explained above, according to this embodiment, two
By taking the average value of the individual flow rate data, it is possible to obtain flow rate data that does not include abnormal data, so that stable flow rate measurement can be performed.

By performing the processing of this embodiment, as shown in Fig. 6, the flow rate signal _I0 maintains output stability even when sudden noise of several milliseconds is introduced, as in the conventional example and the example. I was able to do that. Note that Fig. 5 shows the case where the sampling time ts becomes long, but on the contrary, when it becomes short, the output of the conventional example shown in Fig. 6 suddenly changes in the negative direction, but as mentioned above, the output stability Needless to say, we aim to

Further, in this embodiment, the number of storage areas for the flow rate signal data is six, but it goes without saying that the same effect can be obtained by removing an even number of minimum and maximum values.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, when the suddenly changed flow rate data is taken into the storage area and rearranged from the minimum value to the maximum value, it becomes the minimum value or the maximum value, or The values will be arranged according to that value.
Therefore, since the two pieces of data placed in the center of the storage area cannot correspond to sudden changes, stable flow rate measurement can be performed.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the electromagnetic flowmeter according to the present invention, FIGS. 2 1 to 3 are flowcharts showing the operation of the electromagnetic flowmeter, and FIGS. 3 and 4 show the electromagnetic flowmeter in normal operation. Waveform diagram of each part of flowmeter,
FIG. 5 is a waveform diagram of each part of the electromagnetic flowmeter when an instantaneous power failure occurs, and FIG. 6 is a graph showing the effects of the electromagnetic flowmeter according to the present invention. 1... Excitation coil, 2... Insulated conduit, 3a, 3
b... Electrode, 4... Microprocessor, 5...
Excitation signal control circuit, 6... Excitation circuit, 7... Preamplifier, 8... Inverting amplifier, 9 to 12... Semiconductor switch, 13... A/D converter, 14... D/
A converter, 15... storage device.

Claims (1)

[Claims] 1 A detector consisting of a conduit through which the measurement fluid passes, an excitation coil that applies a magnetic field in the radial direction of the conduit, and a pair of electrodes provided on the conduit surface perpendicular to the direction of the magnetic field and the axial direction of the conduit, and In an electromagnetic flowmeter that calculates the integral value difference of a signal obtained from an electrode and extracts it as a flow rate signal, an even number of at least 6 or more storage areas for the flow rate signals to be sequentially captured are provided, and the areas are arranged sequentially from the minimum value to the maximum value. An electromagnetic flowmeter characterized in that the electromagnetic flowmeter is equipped with means for handling the average value of two values placed in the center as a flow rate signal.