JPS6111611Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an insertion type electromagnetic flowmeter that is inserted into piping to measure the flow rate of fluid.

The following three types of noise can be cited as noise in an insertion-type electromagnetic flowmeter that measures the flow rate of fluid in a pipe.

a Electromagnetic induction noise caused by using a sine wave alternating current as the excitation power source to form a magnetic field b Electrostatic induction noise induced in the electrode by applying voltage to the excitation coil c Electrochemical phenomena between the electrode and the fluid Electrochemical noise based on electrochemical noise Because these noises vary greatly depending on the type of fluid in the pipe or the installation environment of the electromagnetic flowmeter, zero point adjustment is required every time a flowmeter is installed or replaced. Therefore, accurate zero point adjustment has been performed by inserting a flow meter into a pipe during which fluid is moving and temporarily stopping the movement of the fluid within the pipe. As is well known, insertion-type electromagnetic flowmeters have the advantage of being extremely easy to install into existing piping while fluid is being transferred; however, accurate zero point adjustment cannot be made without interrupting the movement of fluid within the pipes. Therefore, the features could not be fully utilized, and for example, when installation work was required due to a water outage, some deviation of the zero point had to be adjusted as it was unavoidable.

The present invention has been made in view of the above points, and aims to provide an insertion type electromagnetic flowmeter that can eliminate the influence of various noises and perform zero point adjustment without interrupting the movement of fluid in the pipe.

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

The figure is an electric circuit diagram showing the configuration of the insertion-type electromagnetic flowmeter according to the present invention, in which the detection part 2 of the electromagnetic flowmeter is inserted inside the pipe 1 that is transferring fluid, and a magnetic field is applied inside the detection part 2. Excitation coil 3 for forming
Further, electrodes 4 are provided on both outer surfaces of the detection section and are in contact with the fluid within the tube. Both of these exciting coils 3 and electrodes 4 are connected to a converter 5, and the output of the electrodes 4 is applied to an arithmetic circuit 6 in the converter 5 to perform the arithmetic operations necessary to calculate the flow rate of the fluid in the pipe. After the change is made, it is arranged to be displayed by a display instrument 10 outside the converter through a variable resistor 8 for zero point adjustment,
On the other hand, the excitation coil 3 is connected via a switch 7 in the converter 5 to the output end of a signal generator 9 which supplies a square wave current, and is supplied with an excitation current. Here, the switch 7 is provided on the ground side of the signal generator 9.

The operation of the insertion type electromagnetic flowmeter according to the present invention constructed as described above will be explained below.

First, the signal generator 9 is oscillated to supply a square wave voltage necessary for operation to the arithmetic circuit 6, and the switch 7 is closed to apply a square wave current necessary for flow rate detection to the excitation coil 3. As long as this square wave current has an appropriate period within a range that does not cause polarization, the polarity may alternately change, or a direct current with no change in polarity may be applied intermittently. In any case, the arithmetic circuit 6
When the current value becomes sufficiently stable after a predetermined period of time has elapsed from the rise of the current waveform that flows into the signal generator 9 through the switch 7, the voltage signal generated between the electrodes 4, 4 is sampled and, for example, amplified. Add to display instrument 10. At this time, the excitation coil 3 is excited by the square wave current and can remove the above-mentioned electromagnetic induction noise.

Next, when the signal generator 9 is caused to oscillate and current is supplied to the arithmetic circuit 6, and the switch 7 is opened, no current is supplied to the excitation coil 3, so no magnetic field is generated. However, since the excitation coil is connected to the signal generator 9 through the line on the side where the switch 7 is not inserted, the same voltage as when measuring the flow rate is applied, causing electrostatic induction noise to the electrode 4. On the other hand, electrochemical noise has been generated between the electrodes 4 from the beginning. That is, if the switch 7 is opened while the signal generator 9 continues to oscillate, the magnetic field will not act on the fluid, and therefore electrostatic induction noise and electrochemical noise that does not include the fluid flow rate signal will be generated. The sum of the noises becomes the output of the arithmetic circuit 6. Therefore, by adjusting the variable resistor 8 to make the indicated value of the display meter 10 zero, the zero point adjustment is performed with the above-mentioned noise value corrected.

After performing such zero point adjustment, by closing the switch 7, the correct flow rate value of the fluid in the pipe will be displayed on the meter 1.
Displayed as 0.

As is clear from the above explanation, the insertion-type electromagnetic flowmeter of the present invention uses square wave current, so high electromagnetic induction noise can be removed, and the flow of fluid in the pipe is not interrupted. Zero point adjustment can be performed extremely easily.

Furthermore, if the zero point adjustment of the variable resistor 8 is not performed at all with the signal generator 9 oscillating and the switch 7 open, the sum of electrostatic induction noise and electrochemical noise will be displayed on the display meter 10. , these noise levels can be measured indirectly, and at the same time, it can also be used as a means to investigate the cause of noise generation.

[Brief explanation of the drawing]

The figure is an electrical circuit diagram showing the configuration of an insertion type electromagnetic flowmeter according to the present invention. 1... Piping, 2... Detection unit, 3... Excitation coil, 4... Electrode, 5... Converter, 6... Arithmetic circuit, 7... Switch, 8... Variable resistance, 9... Signal generation Instrument, 10...display instrument.

Claims (1)

[Scope of utility model registration request] In an electromagnetic flowmeter that measures the flow rate of a fluid to be measured in a pipe by inserting an electrode and an excitation coil into the pipe, a signal generator that supplies a square wave current to the excitation coil, and a ground side between the coil and the signal generator. 1. An insertion-type electromagnetic flowmeter comprising: a switch provided in a line, the switch being opened to adjust the zero point of an indicator.