JPH04198718A - Vortex flow meter - Google Patents

Abstract

PURPOSE:To measure the flow quantity jointly for a liquid and a gas with the same pipe by converting the flow quantity of a measured fluid into a vortex signal, automatically judging whether the fluid is the liquid or the gas from this vortex signal, and switching band filter circuits. CONSTITUTION:An AC vortex signal Vs corresponding to the measured flow quantity is outputted from an adder 22. The vortex signal Vs is compared with a preset value by a judging means 47, and control signals CS1, 2 corresponding to whether the fluid is a liquid or a gas are outputted from a logical circuit 48. The signal Vs is outputted to a filter 38 from a switch SW1 for the gas or to a filter 39 from a switch SW2 for the liquid, it is converted into the frequency signal Fv by a Schmitt trigger circuit 40, it is converted into the voltage signal through a switch SW3 via the signal CS2 for the gas or through a switch SW4 via the signal CS1 for the liquid, and the flow quantity signal is outputted via a voltage/current converting circuit 43. The classification of the measured fluid is automatically judged, and the corresponding flow quantity signal is outputted.

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. 5 and 6 below.
This will be explained using figures.

FIG. 5 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 a 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 on the flange portion 14 side of the vortex generator 12. A pair of piezoelectric elements 16.17 are arranged vertically at a predetermined interval in this recess 15, and these piezoelectric elements 16.1
7 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 16.1
7, the piezoelectric material sandwiched between the upper and lower electrodes on the left side and the piezoelectric material sandwiched between the upper and lower electrodes on the right side are polarized in opposite directions. Generates a polar charge.

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

Charges QVl and QV2 having a frequency corresponding to the vortex frequency of the vortex signal generated in the piezoelectric element 16.17 of the vortex sensor are input to a 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 together in an adder 22, and the added output is filtered into low-frequency r waves by a low-pass filter 23, and then sent to the amplifier 2.
4, it is amplified to a predetermined size.

The output of the amplifier 24 is input to a Schmitt trigger 25 having a predetermined steresis width, and a vortex signal having an amplitude greater than the steresis width is converted into a pulse signal corresponding to the vortex frequency in a 1:1 ratio.

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

This voltage signal is converted into 'r&output I[ by controlling the base current of the transistor 31 by the DC amplifier 30 whose zero point is set by the regulator 29, and output terminals T1 and T2 from the collector and emitter terminals. The signal is transmitted to a receiving resistor RL of a receiving instrument having an external power source Es. In this case, a feedback resistor R/ 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 at this input terminal is It is controlled by a unified t current output IL of 4-20 mA corresponding to the signal.

Mana! Approximately 4 mA of the base portion of the output IL is used to generate an internal power supply for the conversion circuit. That is,
A part of this current is passed through the constant current circuit 32 to the constant voltage circuit 3.
The group 2I supplied to 3 and generated here! A voltage is used to generate zero voltage across the volume 29. Furthermore, 4m
The other part of t7X of A is supplied to the transistor 34 and input to the AC/DC conversion circuit 35, where it is converted to an AC voltage, and this converted AC voltage is sent to the internal power supply circuit 37 via the transformer 36. Supplied. Internal power supply circuit 37
creates an internal voltage V, -■ necessary for the operation of the conversion circuit.

<Problems to be Solved by the Invention> However, although the above-described vortex flowmeter can measure the flow rate of fluids such as gas, steam, and liquid,
Since the vortex frequencies generated by waste (including steam) and liquid are different, the circuit configurations for processing these signals are also different. In other words, the signal processing circuits for liquid and gas are different.

Therefore, when liquid and gas flow in the same pipe,
There was the trouble of having to replace the signal processing circuit each time.

Means for Solving the Problems> In order to solve the above problems, the present invention provides a signal conversion means that converts a measured flow rate into an alternating current vortex signal and outputs it, and a first switch to which this vortex signal is input. A first series circuit in which a first bandpass filter is connected in series, and a second switch and a second bandpass filter having a different band from the first bandpass filter are connected in series to form a first series circuit. A second series circuit connected in parallel, and these first and second series circuits.
Frequency detection means receives the output of the bandpass filter and outputs it as a frequency signal; frequency/voltage conversion means receives the frequency signal and converts it into a voltage signal corresponding to the measured flow rate and outputs it as a flow rate signal; The input signal is compared with a predetermined set value that distinguishes whether the fluid to be measured is a liquid or a gas.When the fluid is a liquid, a first control signal is generated to open and close the first switch.When the fluid is a gas, a second control signal is generated to open and close the second switch. The apparatus further includes a determination means for outputting the output.

<Operation> The signal processing means converts the flow rate of the measured fluid into an alternating current vortex signal, and this vortex signal is changed in frequency by the first and second control signals output by the discriminating means depending on whether the measured fluid is liquid or gas. Two band pass filters with different bands are automatically switched to output the frequency / to the pressure converting means.

The frequency/voltage conversion means outputs a flow rate signal of the measured fluid at a frequency corresponding to the type of the measured fluid.

<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. Note that parts having the same functions as those in the conventional configuration are designated by the same reference numerals, and the description thereof will be omitted as appropriate.

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 38 and 39, respectively. The band pass filters 38 and 39 each have a center frequency set at a high frequency.The band pass filter 38 is selected for a frequency band that occurs when measuring a gas (steam) flow rate, and the band pass filter 39 is selected for a frequency band that occurs when measuring a gas (steam) flow rate. Each frequency band is selected according to the frequency band that occurs.

In the case of a vortex flowmeter, the center frequency depends on the diameter or the measured fluid; for example, in the case of a diameter of 200A, it is 1.75Hz for liquid, about 30Hz for gas, and for a diameter of 15A, it is about 30Hz. , 31.4 when liquid
In the case of gas, the frequency is selected to be about 502 Hz.

The other ends of the bandpass filters 38 and 39 are connected to the input end of a Schmitt trigger circuit 40, and the output end thereof is connected to one end of the switches SW3 and SW4.

The other ends of the switches SW3 and SW4 are respectively connected to one end of a frequency/voltage conversion circuit 41 and 42, and the other ends are both connected to a voltage/current conversion circuit 843.

The output end of the voltage/current conversion circuit 43 is connected to the flow rate output end 44.

On the other hand, the output end of the adder 22 is connected to a rectifier circuit 46 via an amplifier 45, this output end is connected to one end of the input of a comparator 47, and the other end is connected to a constant voltage Eb through a resistor R1.
, R2 are connected to the voltage dividing point. The output terminal of the comparator 47 is connected to the input terminal 11 of the logic circuit 48.

Further, the output frequency Fv of the Schmitt trigger circuit 40 is outputted to the window comparator 50 via the frequency/voltage conversion circuit 49.

Constant voltage Bb is divided by resistors R3, R4, and R5, and the divided voltage between resistors R3 and R4 is the voltage of operational amplifier Q1, which has resistor R6 connected to its output terminal and non-inverting input terminal (10). The divided voltage between resistors R4 and R5 is applied to the non-inverting input terminal (+) of the operational amplifier Q2, which has a resistor R7 connected to its output terminal and non-inverting input terminal (+), respectively. is being applied.

Further, the output end of the frequency/voltage conversion circuit 49 is connected to the inverting input end (-) of the operational amplifiers Q1 and Q2, respectively. The output terminal of the operational amplifier Q1 is connected to the input terminal 2 of the logic circuit 48, and the output terminal of the operational amplifier Q2 is connected to the logic circuit 48.
is connected to the input terminal I3 of.

Switches SW2 and SW4 are connected to the output terminal Q of the logic circuit 48.
A control signal C3I is output to each of them to control opening and closing thereof. Further, a control signal C32 obtained by inverting the control signal C81 via the inverter 51 is output as a control signal for controlling the opening and closing of the switches SWI and SW3.

Next, the operation of the vortex flowmeter configured as described above will be explained using the truth value diagram shown in FIG. 2 and the characteristic diagram of the flow rate measurement range shown in FIG. 3.

An alternating current voltage corresponding to the measured flow rate is generated at the output end of the adder 22 as an alternating current vortex signal Vs.

When the fluid to be measured is gas (including steam), this vortex signal Vs is output to the switch SWI by the control signal C32.
is turned on and output to the bandpass filter 38.

This bandpass filter 38 removes unnecessary noise and outputs it to the Schmitt trigger circuit 40, where the vortex signal is set at an output frequency Fv corresponding to the measured flow rate. The maximum frequency of the output frequency Fv at this time is Fg as shown in Figure 3.
m and the minimum frequency is Fgn.

Furthermore, the measured output frequency Fv is turned on by the control signal C32 which is turned on when the gas is on, and the switch SW3 is turned on and outputted to the frequency/voltage conversion circuit 41, where it is converted into a voltage signal and is converted into a voltage/current conversion circuit. 43 to the flow rate output end 44 as a flow rate signal Qvl.

Next, when the measured fluid is liquid, rlJflll signal C8
1 turns on the switch SW'2, and the vortex signal VS is output to the bandpass filter 39. This bandpass filter 39 removes unnecessary noise from the eddy signal and outputs it to the Schmitt trigger circuit 40, where it is set to an output frequency Fv corresponding to the measured flow rate. Output frequency F at this time
As shown in FIG. 3, the maximum frequency of v is Ffm and the minimum frequency is Ffn.

Further, the measured output frequency Fv is turned on by the control signal C3I that is turned on when the liquid is present, and the switch SW4 is outputted to the frequency/voltage conversion circuit 42, where it is converted into a voltage signal, and the voltage/ is converted into a current. It is output as a flow rate signal Qv2 to the flow rate output end 44 via the circuit FI&43.

Therefore, as shown in Figure 3, when the output frequency FV is very large, it means that the gas flow rate is being measured.
When it is very small, liquid is measured, and when it is in the intermediate frequency range shown by range S, there are times when it is gas and times when it is liquid.

Next, a discriminating means for discriminating whether the range being measured is liquid or gas will be explained.

The amplitude of the vortex signal Vs is input to a rectifier circuit 46 via an amplifier 45.
is input to the circuit and rectified here, and its output is the voltage Va
A comparator 47 compares the constant voltage Eb with a divided voltage Vdl obtained by dividing the constant voltage Eb by resistors R1 and R2, and outputs it from its output terminal to the input terminal 11 of the logic circuit 48 as a comparison signal Cot. In this case, the divided voltage Vdl is the density ρ×(
The minimum flow rate of gas) is set to a value corresponding to 2.

Further, the output frequency Fv of the vortex signal Vs is converted into a voltage signal by the frequency/voltage conversion circuit 49, and the inverting input terminals (-
) is output as a frequency voltage vb, and this frequency voltage v
b is compared with the divided voltages Vd2 and Vd3 obtained by dividing the constant voltage Eb by resistors R3, R4, and R5, and the operational amplifiers Q1 and Q
The comparison signals CO2 and CO3 are outputted from the respective output terminals of the logic circuit 48 to the input terminals I2 and 3 of the logic circuit 48, respectively. In this case, the partial voltage Vd2 is the voltage Vfm corresponding to the highest flow rate corresponding to the highest frequency Ffm of the measured liquid, and the partial voltage Vd3 is the voltage Vfm corresponding to the lowest flow rate corresponding to the lowest frequency Fgn of the measured gas.
Set to g and n respectively.

Logic circuit 48 performs logic operations corresponding to the truth diagram shown in FIG.

When the comparison signals CO2 and CO3 are both at low level L, the frequency voltage vb shows a value larger than Vd2, so the logic circuit 48 assumes that gas is being measured.
sets the control signal C3I to a high level H regardless of the magnitude of COI, and converts the control signal C32 to a low level L to turn on the switches SWI and SW3.

Next, when the comparison signals CO2 and CO3 are both at high level H, the frequency voltage vb shows a smaller value than Vd3, so the logic circuit 48 assumes that a liquid is being measured and outputs the control signal C3I. Regardless of the size of COI, it is set to low level L and switches SW2 and SW4 are turned on.

Next, when the measurement frequency Fv is in the range of Fgn<Fv<Ffm, it is not possible to determine whether a liquid or gas is being measured just from the magnitude of the measurement frequency Fv. , that is, in this case, the truth table shown in Figure 2 shows the ratio IF5! Signal c02 is high level H″QCO
3 corresponds to the case of low level L.

Therefore, in this case, the determination is made by looking at the amplitude of the vortex signal Vs. The signal corresponding to this amplitude is the comparison signal COI
It is. That is, in this case, it is determined whether it is a liquid or a gas based on the level of the comparison signal C01 in the truth diagram shown in FIG.

The amplitude voltage Va is compared with a partial voltage Vdl set to a value corresponding to the density ρ of the measurement fluid x (flow velocity corresponding to the lowest frequency Fgn of gas) 2, and is output as a comparison signal C01. In general, in the case of a liquid, its density ρ is larger than that of a gas, but its output frequency is smaller, and conversely, in the case of a gas, its density ρ is smaller but its output frequency is larger. With the density ρ set to a value corresponding to , it is determined whether it is a liquid or a gas.

When the amplitude voltage Va is larger than the partial voltage Vdl, it is determined that the density ρ is large and it is determined to be a liquid, and when the opposite is the case, it is determined that it is a gas. In other words, as shown in FIG.
When OI is low level L, control signal C81 is used as a liquid.
When the comparison signal COI is at a high level H, it is determined that it is gas, and the control signal C3I outputs a control signal that makes the control signal C32 a high level H1, that is, a control signal that sets the control signal C32 to a low level L.

As described above, the logical operation of the logic circuit 48 according to the truth diagram shown in FIG. 2 automatically determines whether the measured fluid is liquid or gas, and outputs a corresponding flow rate signal.

FIG. 4 is a block diagram showing the configuration of another embodiment of the present invention. In this case, whether the measured fluid is a liquid or a gas is determined by paying attention to the difference in density.

The vortex signal Vs is amplified by an amplifier 52, and further outputted to an inverting input terminal (-) of a comparator 54 as a density signal Vm via a second-order low-pass filter 53.

On the other hand, the comparator 54 connects the constant voltage Eb to the resistors R8 and R9.
The divided voltage V divided by and applied to the non-inverting input terminal (+)
d4 and the density signal Vm, and outputs the comparison result to the switches SW1 and SW3 as a control signal C34, and the control signal C3 whose level is inverted via the inverter 55.
3 is output to switches SW2 and SW4. In this case, the partial voltage Vd4 is set to a voltage corresponding to a predetermined value that can distinguish between gas and liquid.

The vortex signal Vs has an amplitude proportional to ρV2, where ρ is the density and V is the flow velocity, so if it is extracted through a first-order filter, it becomes a signal proportional to ρV, and then it is passed through the first-order filter again. By passing the signal through a second-order filter as a whole, a signal proportional to the density ρ is obtained.

Therefore, the output of the low-pass filter 53 has a density signal Vm
can be obtained.

When the density signal Vm smaller than the predetermined divided voltage Vd4 is output from the low-pass filter 53, the comparator 54 determines that the fluid to be measured is gas, sets the control signal C84 to high level H, and turns on the switches SW1 and SW3. . In the opposite case, assuming that the liquid is liquid, the control signal C34 is set to low level L, that is, the control signal C33 is set to high level H, and the switches SW2 and SW4 are turned on.

Through the above operations, it is possible to automatically discriminate between liquid and gas and output the measured flow rates for each.

<Effects of the Invention> As specifically explained above in conjunction with the embodiments, according to the present invention, it is possible to automatically determine whether the measured fluid is a liquid or a gas using the vortex signal itself of the measured fluid. Even when liquid and gas (including steam) flow separately, the flow rate can be measured as a vortex flowmeter without distinguishing between liquid and gas and without requiring any adjustment.

[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 truth diagram explaining the operation of the embodiment shown in FIG.
FIG. 3 is an explanatory diagram explaining the measured flow rate range of the embodiment shown in FIG. 1, FIG. 4 is a block diagram showing the configuration of another embodiment of the present invention, and FIG. A 1:1 sectional view showing the configuration of the vortex sensor part, and FIG. 6 is a block diagram showing the overall configuration of a conventional vortex flowmeter. 16.17... Piezoelectric element, 19.20... Charge converter, 22... Adder, 25... Schmitt trigger, 38.39... Band pass filter, 40...
... Schmitt trigger circuit, 47... comparator,
48...Logic circuit, 50...Window converter, 53...Low pass filter, 54...Contractor. Figure 2 3 [a1 111 → 1 vortex frequency (Fv) 5th ['

Claims (1)

[Claims] a signal conversion means for converting the measured flow rate into an alternating current vortex signal and outputting it; a first series circuit to which the vortex signal is input and a first switch and a first bandpass filter are connected in series; and a second switch. a second series circuit in which a second bandpass filter having a band different from that of the first bandpass filter is connected in series and connected in parallel to the first series circuit; a frequency detection means that receives the output of the pass filter and outputs it as a frequency signal; a frequency/voltage conversion means that receives the frequency signal and converts it into a voltage signal corresponding to the measured flow rate and outputs it as a flow rate signal; and the vortex signal. is input and compared with a predetermined setting value that distinguishes whether the fluid to be measured is a liquid or a gas.
A vortex flow meter characterized by comprising: a discrimination means for outputting a first control signal for opening and closing a switch, and a second control signal for opening and closing the second switch when gas is detected.