JPH0351703Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a measuring device that measures the process amount of a fluid to be measured in a process piping system via a wetted electrode. This invention relates to means for avoiding the occurrence of abnormalities.

[Technical background of the invention and its problems]

In a measurement device that measures process quantities such as the electrical conductivity and flow rate of a conductive fluid to be measured in a process piping system via a wetted electrode, if periodic disturbances exist, this periodic disturbance will cause the measurement signal to This may cause abnormalities in measurement results. Periodic disturbance elements include electric fields, magnetic fields, vibrations, pressure, and the like.

[a] In the case of electric fields: When a measuring device is used in an environment where it is difficult to ground, such as the upper floors of a high-rise building, incomplete grounding has been a problem.

[b] For magnetic fields: If the measuring device is used near a large thyristor-driven motor, a large-scale magnetic shield is required, so it must be placed in a large magnetic container or compensated using a compensation search coil. It was very difficult. Particularly in electrical conductivity measurements, the pair of electrodes, including the fluid resistance between the electrodes, form a one-turn coil, making it difficult to escape from the magnetic field.

[c] In the case of vibration: When using a measuring device at a site where there is ground vibration over a wide area, such as a continuous foundry or a large hydroelectric power plant, the output may fluctuate due to vibrations in circuits, wiring, etc. This caused problems with precision measurements.

[d] For pressure: The pressure in the process piping fluctuates, the electrochemical activity of the electrode surface of the measuring device changes, electromotive force noise corresponding to the pressure is generated, and in some cases measurement errors may occur. There was a problem with the size of the product, and the measuring device could only be used as a guide.

[Purpose of invention]

An object of the present invention is to provide a measuring device that can avoid abnormalities in measurement results caused by periodic disturbances even in an environment with periodic disturbances as described above.

[Summary of the idea]

The present invention comprises a process piping system having a detection section in which an electrode is placed in contact with the fluid to be measured in the pipe, and an alternating power generation section for supplying alternating power for the detection section necessary for measurement. In a measuring device in which a periodic disturbance from the electrode of the detection section is superimposed on the measurement signal during process quantity measurement, causing an abnormality in the measurement result, the frequency of the periodic disturbance and the alternating power for the detection section are A measuring device comprising a disturbance avoidance processing section that detects a frequency of disturbance that interferes with the frequency and causes an abnormality in the measurement result, and shifts the frequency of the alternating power for the detection section to a frequency that does not cause an abnormality in the measurement result. was realized and the intended purpose was achieved.

[Example of idea]

Embodiments of the present invention will be described below with reference to the drawings.

A measuring device according to an embodiment of the present invention is shown in FIGS. 1 and 2.
As shown in the figure. FIG. 1 is a block diagram showing the overall configuration, and FIG. 2 is a detailed diagram showing an example of the detection section of FIG. 1. In Figure 1, 1 is a process piping system 2
10 is a converting unit that converts the output signal 14 of the detecting unit 1 into an output signal 16 of the measuring device; 11 is a periodic converter; An abnormality detection unit receives a disturbance signal from a disturbance detection unit 23 that detects disturbance, and determines that an abnormal state has occurred when the frequency of this disturbance signal matches the frequency that causes an abnormality in the measurement result. This is a clock section that shifts the frequency of the alternating power for the detection section of the alternating power generation section 13 to a frequency that does not cause abnormalities in the measurement results in response to a frequency change command output at the time of detection. The above abnormality detection section 11 and clock section 12 constitute a disturbance avoidance processing section 15.

FIG. 2 shows an example of the detection section 1, in which a pair of electrodes 6, 6' are provided facing each other in a process piping system 2 consisting of a pipe 3 provided with an insulating lining 4. The electrical conductivity of the fluid to be measured is measured by detecting the fluid electrical resistance 7 between the two points as a piece of a Wheatstone bridge. As the power source for Wheatstone Bridge, the alternating power generation section 1 shown in Figure 1 is used as the power source for the Wheatstone Bridge.
For example, a 50 Hz alternating power 8 for the detection section is supplied from the power source 3.

The converter 10 includes a bandpass filter 9 and a converter circuit 10A, and the bandpass filter 9 mainly passes the frequency of the alternating power 8 for the detector, and passes frequencies apart from the frequency of the alternating power 8 for the detector. It is configured so that it cannot pass through.

In the measuring device of the embodiment of the present invention configured as described above, when a periodic disturbance acts on the process piping system 2, the alternating power 8 for the detection section and the periodic disturbance interfere, causing an abnormal error. This may occur. The case where an electric field or a magnetic field acts as a periodic disturbance is common sense, so it is omitted, and an example of pressure will be described here.

Examples of periodic pressure fluctuations that occur in the process piping system 2 include when fluids containing sewage or solid slurry are delivered using a piston pump, when chemicals are delivered using a piston-type metering pump, or when pumping fluids to a reservoir on a high mountain. There are cases where water is raised using a rotary piston pump, and recently, the pump speed of the pumps used in these applications is often varied using a mechanical remote drive continuously variable transmission or thyristor speed control. When the load on the pump discharge side is large, the pressure at the pump outlet is high, the pressure on the pump discharge side pulsates, and the flow rate also fluctuates.

Such pressure fluctuations and flow rate fluctuations in the process piping system 2 disturb the electrochemical stability of the surfaces of the liquid contact electrodes 6, 6', changing the electrochemical activity, and when the pressure is constant, the electrochemical activity changes. The electrochemical electromotive force fluctuates in response to pressure fluctuations, resulting in cyclic fluctuations in electrode potential, that is, electrochemical fluctuation noise.

Now, the pressure frequency in the process piping system 2 is the frequency of the alternating power 8 for the detection part (50Hz in this example).
, the pulsation of the electrochemical electromotive force, that is, the electrochemical fluctuation noise, and the frequency of the alternating power 8 for the detection unit may interfere with each other, and the measurement device output 16 output from the conversion unit 10 may fluctuate greatly. be.

In the measuring device of this embodiment, the disturbance detection section 2
3, the frequency of pressure fluctuation within the process piping system 2 is detected and sent to the abnormality detection section 11. The abnormality detection unit 11 detects that the input frequency matches the frequency at which the frequency of electrochemical fluctuation noise based on pressure fluctuations and the frequency of the alternating power 8 for the detection unit interfere with each other, causing abnormal fluctuations in the output of the measuring device, for example, 50 Hz. When,
It is determined that an abnormal condition has occurred, and a frequency change command 20 is output and sent to the clock section 12. The clock section 12 receives the frequency change command 20 and starts the alternating power generation section 13.
The frequency of the alternating power 8 for the detection section is changed to a preset frequency at which no abnormality occurs, for example, 40 Hz. At the same time, the abnormality detection unit 11 also switches the bandpass filter 9 to 40Hz. This results in
Interference between the electrochemical fluctuation noise and the alternating power 8 for the detection section disappears, and fluctuations in the output 16 of the measuring device disappear.

Note that the present invention is not limited to the above-described embodiments, and can be implemented with modifications as described below.

[a] The disturbance detection unit 23 is not limited to one that directly detects the frequency of pressure fluctuations, but also receives a synchronization signal from the crankshaft of the piston of a piston pump or the rotating shaft of an electric motor, and converts it into the frequency of pressure fluctuations based on this signal. It can be anything.

[b] The measurement device output signal 16 output from the conversion section 10 is input to the abnormality detection section 11, and when a fluctuation occurs in the measurement device output signal 16, it is determined that an abnormal state has occurred, and the clock section 12 is activated. The frequency of the alternating power 8 for the detection section outputted from the alternating power generating section 13 under control is continuously changed, and the frequency change is stopped at a frequency at which fluctuations in the measuring device output signal 16 disappear. The alternating power generating section 13 may supply the alternating power 8 for the detection section.

[c] In the above-mentioned embodiment, the measurement of electrical conductivity was explained as an example of the detection unit 1, but the same applies to flow rate measurement using an electromagnetic flowmeter excited using a low frequency power supply as the alternating power supply 8 for the detection unit. It can be implemented by

[Effect of idea]

As described in detail above, according to the present invention, the process piping system includes a detection section in which an electrode is placed in contact with the fluid to be measured in the pipe, and an alternating power generation section that supplies alternating power for the detection section necessary for measurement. In a measuring device in which a periodic disturbance from the electrode of the detection section is superimposed on the measurement signal and causes an abnormality in the measurement result when measuring the process amount of the fluid to be measured, the periodic disturbance is a disturbance avoidance processing unit that detects a frequency of disturbance that causes an abnormality in the measurement result due to interference between the frequency of the alternating power for the detection unit and the frequency of the alternating power for the detection unit, and shifts the frequency of the alternating power for the detection unit to a frequency that does not cause an abnormality in the measurement result; By providing this, it is possible to avoid occurrence of abnormalities due to disturbances in the measurement results of the measuring device that measures the process amount of the fluid to be measured in the process piping system in an environment where periodic disturbances exist. , it becomes possible to maintain measurement accuracy.

[Brief explanation of the drawing]

1 and 2 show a measuring device according to an embodiment of the present invention, FIG. 1 is a block diagram showing the overall configuration, and FIG. 2 is a detailed view showing an example of the detection section of FIG. 1. 1...detection section, 2...process piping system, 3...
Pipe, 6, 6'... Electrode, 8... Alternating power for detection section, 10... Conversion section, 11... Abnormality detection section, 1
2... Clock section, 13... Alternate power generation section, 1
4...Output signal of the detection section, 15...Disturbance avoidance processing section, 16...Measuring device output, 20...Frequency change command, 23...Disturbance detection section.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) The process piping system has a detection section in which an electrode is placed in contact with the fluid to be measured in the pipe, and an alternating power generation section that supplies alternating power for the detection section necessary for measurement. In a measuring device in which a periodic disturbance from the electrode of the detection section is superimposed on the measurement signal and causes an abnormality in the measurement result when measuring the process amount of the fluid to be measured, the frequency of the periodic disturbance and It has a disturbance avoidance processing unit that detects a frequency of disturbance that interferes with the frequency of the alternating power for the detection unit and causes an abnormality in the measurement result, and shifts the frequency of the alternating power for the detection unit to a frequency that does not cause an abnormality in the measurement result. A measuring device characterized by: (2) When the disturbance avoidance processing unit receives a disturbance signal from the disturbance detection unit that detects periodic disturbances and the frequency of this disturbance signal matches the frequency that causes an abnormality in the measurement result, the disturbance avoidance processing unit determines that an abnormal state has occurred. It comprises a detection section, and a clock section that shifts the frequency of the alternating power for the detection section of the alternating power generation section to a frequency that does not cause an abnormality in the measurement results in response to a frequency change command output from the abnormality detection section when an abnormality is detected. A measuring device according to claim 1 of the utility model registration claim, characterized in that: