JPH0465633A - Vortex flow meter - Google Patents

Abstract

PURPOSE:To eliminate the trouble of replacing a signal processing circuit corresponding to the kind of fluid and to prevent misadjustment by discriminating the kind of the fluid and switching the signal processing circuit automatically. CONSTITUTION:A decision circuit 47 which decides the kinds of, for example, steam and liquid is composed of switches SW1 and SW2, a comparator 45, an inverter 46, etc. Charge signals from piezoelectric elements 16 and 17 are converted by charge converters 19 and 20 into voltage signals, which are added by an adder 22 to obtain a good-S/N vortex signal. A temperature detecting element 39, on the other hand, discriminates between the steam and liquid according to the output of the comparator 45 which is, for example, low in level for the steam and high for the liquid. The switch SW1 is turned on for the steam and the switch SW2 is turned on for the liquid according to the difference in level, thereby performing automatic switching.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a vortex flowmeter that converts the flow rate of a measured fluid into an electrical signal, and particularly relates to a vortex flowmeter that converts the flow rate of a measured fluid into an electrical signal, and in particular automatically determines the type of measured fluid and generates a corresponding flow rate signal. This paper relates to a vortex flowmeter that has been improved to be able to output .

<Prior art> The configuration of a conventional vortex flow rate converter is shown in Figs. 3 and 4 below.
This will be explained using figures.

FIG. 3 is a vertical sectional view showing a cross section of a conventional vortex sensor.

10 is a conduit through which fluid flows, and 11 is an inner cylindrical nozzle provided perpendicular to the conduit 10. Reference numeral 12 designates a columnar vortex generating body having a trapezoidal cross section inserted perpendicularly into the conduit 10 at a distance from the nozzle 11, one end of which is fixed to the conduit 10 with a screw 13, and the other end of which is fixed to the conduit 10 with a flange portion 14. It is fixed to the nozzle 11 by screws or welding. 15 is a recess provided in the flange portion 14fill of the vortex generator 12. A pair of piezoelectric elements 16 and 17 are arranged vertically at a predetermined interval in this recess 15, and these piezoelectric elements 1
6.17 is insulated and sealed with a sealing body 18 such as glass. In the piezoelectric elements 16 and 17, semicircular electrodes divided into two are arranged on the upper and lower sides, respectively. Each piezoelectric element 1
6.17 shows that the piezoelectric material sandwiched between the upper and lower S poles on the left side and the piezoelectric material sandwiched between the upper and lower electrodes on the right side are polarized in opposite directions, and the upper and lower sides of each other are polarized in response to stress in the same direction. Generates a charge of opposite polarity on the electrode.

The vortex signal from the vortex sensor configured as described above is input to the conversion circuit shown in FIG. 4.

Electric currents 'RQv+, Qv2 with frequencies corresponding to the vortex frequency of the vortex signal generated in the piezoelectric elements 16 and 17 of this vortex sensor
is input to the charge converter 19, 20 and converted into an alternating current voltage signal. The voltage signal of the charge converter 19, the voltage signal of the charge converter 20, and the voltage signal passed through the volume controller 21 are added in an adder 22, and the added output is filtered into a low-frequency P wave by a low-pass filter 23, and then sent to an amplifier 24. is amplified to a predetermined size.

The output of the amplifier 24 is input to a Schmidt driver 25 having a predetermined hysteresis width, and a vortex signal having an amplitude greater than the hysteresis width is converted into a pulse signal corresponding to the vortex frequency of 1=1.

This pulse signal is DC-insulated by a transformer 26 and inputted to a frequency/S pressure converter 27, where a volume 28
is converted into an analog voltage signal corresponding to the span.

This voltage signal is converted into a current output IL by controlling the base current of the transistor 31 by a DC amplifier 30 whose zero point is set by a regulator 29, and is externally transmitted from the collector end and emitter end to the output terminals T1 and T2. Power supply B
S is transmitted to the receiving resistor RL of the receiving instrument. In this case, a feedback resistor Rf is inserted between the transistor 31 and the output terminal T2, and the feedback voltage Ef generated across the feedback resistor Rf is fed back to the input terminal of the DC amplifier 30, and the voltage signal at this input terminal is It is controlled to a unified current output IL of 4 to 20 mA corresponding to .

In addition, approximately 4 mA of the base portion of the output output I is used to create the internal power supply of the conversion circuit. That is,
A part of this current flows through a constant voltage circuit 32 through a constant voltage circuit 32.
Using the reference voltage supplied to and generated therein, zero voltage is generated across the two volumes. Furthermore, a portion of the 4 mA S current is supplied to the transistor 34 to generate an AC/AC current.
The voltage is input to the DC conversion circuit 35, where it is converted into an AC voltage, and the converted AC voltage is supplied to the internal power supply circuit 37 via the transformer 36. The internal power supply circuit 37 generates internal voltages +V and -■ necessary for operation of the conversion circuit.

<Problems to be Solved by the Invention> However, although the above-described vortex flowmeter can individually measure the flow rate of fluids such as steam and liquid, the vortex frequencies generated by steam and liquid are different. Therefore, the same signal processing circuit cannot perform signal processing.

In other words, it is necessary to use separate signal processing circuits for liquid and steam.

Therefore, when different types of fluids, such as liquid and steam, flow into the same pipe, there is a problem in that the signal processing circuit must be replaced and adjusted each time.

Means for Solving the Problems> In order to solve the above problems, the present invention provides a signal converting means for converting the flow rate of a measured fluid into an alternating current vortex signal and outputting the signal, and a signal converting means for measuring the temperature of the measuring fluid. temperature detecting means for outputting the temperature signal as a temperature signal; discriminating means for inputting the Jl signal and the temperature signal and determining the type of fluid to be measured by distinguishing based on the temperature signal; 1st
The apparatus includes a first signal processing means for outputting a flow rate signal, and a second signal processing means for performing signal processing and outputting a second flow rate signal when the measured fluid is of a second type. The device is configured to automatically switch to either the first signal processing means or the second signal processing means, and to ignore either the first flow rate signal or the second flow rate signal.

Function> The signal conversion means converts the flow rate of the measured fluid into an alternating current vortex signal and outputs it, and the temperature detection means measures the temperature of the measured fluid and outputs it as a temperature signal.

Then, the discrimination means uses this temperature signal to distinguish the type of fluid from the difference in temperature of the measured fluid.

Depending on the result of the discrimination by the discrimination means, either the first signal processing means or the second signal processing means is automatically switched to output either the first flow rate signal or the second flow rate signal.

<Examples> Examples of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of one embodiment of the present invention, and FIG.
The figure shows the vortex generator part of the embodiment shown in Figure 1.
11 is a sectional view.

In the following description, parts having the same functions as those in the conventional configuration are denoted by the same reference numerals, and the description thereof will be omitted as appropriate. Furthermore, for convenience of explanation, the description will be made assuming that steam and fluid are flowing through the same pipe.

The output end of adder 22 is connected to one end of switches SWI and SW2, the other ends of which are connected to one end of bandpass filters 40 and 41, respectively.

The temperature detection element 39 is inserted and fixed together with the piezoelectric element 16, 17 into the vortex generator 43 shown in FIG. 2, and detects the temperature of the fluid to be measured. A constant voltage (1) is applied to this temperature detection element 39 via a resistor 44.

The connection point between the temperature detection element 39 and the resistor 44 is connected to the non-inverting input @(+) of a comparator 45 to which the reference voltage 2 is applied to the inverting input terminal (-). The comparison output CO of the comparator 45 controls the opening and closing of the switch SW1 via the inverter 46, and directly controls the opening and closing of the switch SW2. In other words, the comparison output CO controls the switch 5WISW2 in a complementary manner.

These switches swi, SW2, comparator 45, inverter 46, and the like constitute a discrimination circuit 47 that discriminates between steam and liquid, for example.

The bandpass filters 40 and 41 have different center frequencies, and the bandpass filter 4° is selected for the frequency band that occurs when measuring the flow rate of steam (gas), and the bandpass filter 41 is selected for the frequency band that occurs when measuring the flow rate of steam (gas). Each frequency band is selected according to the frequency band that occurs.

In the case of a vortex flowmeter, the center frequency differs depending on the diameter or the measured fluid, but for example, in the case of a diameter of 200A, it is 1.75H2 for liquid and 30H for steam.
When the diameter is 15A, it is about 31 when it is a liquid.
．． When using steam at 4 Hz, the frequency is selected to be about 502 Hz.

The other ends of the bandpass filters 40 and 41 are connected to the input ends of Schmitt trigger circuits 42 and 43, and the output ends thereof are connected to one ends of the switches SW3 and SW4.

The other ends of the switches SW3 and SW4 are respectively connected to one end of a frequency/positive conversion circuit 44, and the other ends are both connected to a voltage/current conversion circuit 45. Further, the outputs of the bandpass filters 40 and 41 are adjusted in size by attenuators 46 and 47 as appropriate.

The input signal of the bandpass filter 40 and the output signal of the Schmitt trigger circuit 42 are input to a noise discrimination circuit 48, which determines whether the input fSd word is caused by noise or not. When it is determined that this is the case, switch SW3 is turned on. Similarly, the input signal of the bandpass filter 41 and the Schmidt Drika circuit 4
The output signal No. 3 is input to a noise discrimination circuit 49, which judges whether the input signal is caused by noise or not. If it is judged that the signal is not caused by noise, switch SW4 is turned on. .

In the above configuration, the charge signals from the piezoelectric elements 16, 17 are converted into voltage signals by the charge converters 19, 20, and added by the adder 22 to form vortex signals with a good S/N ratio. On the other hand, if the resistance value of the temperature detection element 39 at 100°C is set as R1 and the resistance value of the RO5 resistor 44 is set as multi-value so that the relationship RO-Vl/(R1+RO)=V2 is established, the steam In this case, the output of the comparator 45 is, for example, a low level, and in the case of liquid, it is a high level, so that steam and liquid can be distinguished.

Due to this difference in level, in the case of steam, switch SW
In the case of liquid, switch SW2 can be turned on to automatically change these settings.

In the above examples, the measuring fluid is a liquid (T<100°C)
Although the case of 1 and the case of steam have been described, the present invention is not limited to these cases, and the present invention can be applied in the same manner as long as the temperature of the fluid to be measured is different.

Further, the temperature detection element 39 can be appropriately selected from a resistance temperature detector and a thermocouple.

<Effects of the Invention> As specifically explained above in conjunction with the embodiments, according to the present invention, the signal processing circuit is automatically configured to distinguish between the types of fluid by focusing on the fact that the temperature differs depending on the type of fluid to be measured. Since it is designed to switch, even when two types of fluids alternately flow through the same piping, there is no need to change the signal processing circuit according to the fluid type, and problems such as adjustment mistakes are avoided. be able to.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of one embodiment of the present invention, Fig. 2 is a vertical cross-sectional view showing the configuration of the vortex generator used in Fig. 1, and Fig. 3 is the detection end of a conventional vortex flowmeter. FIG. 4 is a block diagram showing the structure of a conventional thin flow meter. 16.17...Piezoelectric element, 19.20...Charge converter, 22...Adder, 25...Schmidt driver, 39...Temperature detection element, 40.41...Band pass filter, 42 .43... Schmidt Drika circuit, 45... Comparator, 47... Discrimination circuit. Agent Patent Attorney Shinsuke Obama 2Lξ臂

Claims (1)

[Claims] a signal conversion means for converting the flow rate of the measurement fluid into an alternating current vortex signal and outputting it; a temperature detection means for measuring the temperature of the measurement fluid and outputting it as a temperature signal; and the vortex signal and the temperature signal are inputted. a discriminating means for discriminating the type of the measured fluid by distinguishing it based on the temperature signal; and a first discriminating means for performing signal processing and outputting a first flow rate signal when the measured fluid is of a first type.
a signal processing means; and a second signal processing means for performing signal processing and outputting a second flow rate signal when the measured fluid is of a second type; Alternatively, the vortex flowmeter is characterized in that it automatically switches to either the second signal processing means and outputs either the first flow rate signal or the second flow rate signal.