JPH0626812Y2 - Vortex flowmeter converter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a liquid which is installed in one vortex flowmeter disposed in a flow tube with a fluid flow rate of either liquid or gas flowing in the same flow tube. And a converter of a vortex flowmeter having a function of automatically switching either of the gas conversion circuits to selectively output a flow rate pulse of a corresponding fluid.

BACKGROUND ART As is well known, a vortex flowmeter is an extremely simple principle in which a vortex generator is mounted in a flow tube, Karman vortices generated and separated from the vortex generator are detected, and the flow rate is calculated from the number of vortices per unit time. The vortex signal can be easily converted to a pulse signal to obtain a digital flow rate signal, and the flow rate range is wide, making it useful as a flow rate detection end in instrumentation.
The types of measurement fluids and the applicable range have been expanded. Also,
The pulse constant of the flow pulse of the vortex flowmeter is determined by the Strouhal number. Since this Strouhal number depends on the Reynolds number, the pulse constant is determined within a certain range of Strouhal number, and the density of gas and liquid is Even in the case of different fluids, there is also an advantage that the flow rate pulse can be calculated and measured without changing the pulse constant in the Reynolds number range,
It has been attempted to measure the flow rates of liquids and gases with a single vortex flowmeter. For example, after repeating measurement of the liquid A, steam cleaning, switching to the liquid B, steam cleaning again, and measurement of the liquid A are repeated. In this case, the flow rates of the liquid A, the liquid B, and the vapor are naturally measured for each liquid.

On the other hand, a method that uses vortex fluctuation pressure or lift change is often used as a vortex detection method for vortices in vortex flowmeters.
These detection signals have signal levels proportional to the fluid density and the square of the flow velocity. In industrial applications, the liquid to be measured is liquid with high density and low flow velocity, but gas has low density and high flow velocity, so the frequency range and signal level in the measurement flow range of the eddy signal between liquid and gas are also different from each other, When measuring the flow rates of liquid and gas with one vortex signal, conventionally, a signal converter for liquid (hereinafter simply referred to as a converter) and a converter for gas are placed side by side, and each converter is switched. Was manually switched at the time of switching the flow path from the fluid source of liquid or gas.

Problems of the Prior Art In the conventional vortex flowmeter described above, there is a trouble of switching the fluid converter at the time of switching the fluid flow path flowing from the fluid source of the liquid or gas into the flow tube, which causes a malfunction. There was also a risk of.

Means for Solving Problems The present invention has been made in view of the above problems, and automatically switches the flow of liquid or gas by using the conversion output of the vortex signal, and only the flow rate signal concerned. It is an object of the present invention to provide a converter incorporating a switching means for outputting a liquid flow pulse for amplifying a vortex signal in a liquid flow range having a low upper limit frequency and an amplification circuit for amplifying the vortex signal. And a conversion circuit for liquid which outputs a high level signal at the time of conversion, a conversion circuit for gas which converts a vortex signal in a gas flow range having a high upper limit frequency into a gas flow pulse, and a conversion circuit for liquid in the amplification circuit. And a gas conversion circuit are respectively connected, and when measuring the liquid flow rate, the gas flow rate pulse output is closed by the high level signal, and only the liquid flow rate pulse signal is output. The gate means outputs only the gas flow rate pulse in the high frequency band without outputting the body flow rate pulse, and determines and outputs the flow rate pulse of the measurement fluid of either liquid or gas.

Embodiment FIG. 1 is a block diagram showing the structure of the vortex flowmeter converter of the present invention, in which 1 is provided in a flow tube (not shown),
A sensor that detects a vortex signal of a vortex flowmeter that measures a liquid or gas flow rate, and the illustrated one is a piezoelectric element sensor that detects a vortex fluctuation pressure as an electric signal. The detection signal is output at a level proportional to the piezoelectric coefficient, the fluid density, and the square of the flow rate. Reference numeral 2 is a charge amplifier that receives a high-impedance piezoelectric signal from the sensor 1 and proportionally amplifies a wide range of vortex frequencies corresponding to the flow rate range of liquid to gas. Reference numeral 3 is a charge amplifier 2 that is connected to the charge amplifier 2 and has a high upper limit frequency. A gas converter that outputs a vortex signal in the range as a gas flow rate pulse, and includes an amplifier 31, a trigger circuit 32, and a digital filter 3.
3 and 3. A liquid converter 4 is a liquid converter that is connected to the charge amplifier 2 and outputs a vortex signal in the flow rate range of the liquid having a low upper limit frequency as a liquid flow pulse. The amplifier 41, the trigger circuit 42, and the digital filter 43 are provided. It consists of The digital filter 43 has a switching signal terminal 43a that outputs a high level signal when measuring a liquid and outputs a low level signal when measuring a gas.
A first AND gate 5 inputs the output of the gas converter 3 and the inverted output of the switching signal via the inverter 7. A second AND gate 6 receives the output of the liquid converter 4 and the switching signal. An OR gate 8 receives the first and second gate outputs and outputs a liquid or gas flow rate pulse from an output terminal 9.

Next, the operation in the above block diagram will be described. The output of the charge amplifier 2 is simultaneously input to the gas amplifier 31 and the liquid amplifier 41.
A high-order low-pass filter is provided for amplifying a high vortex frequency corresponding to a gas flow rate having a large flow velocity, blocking frequency components outside the flow rate range, and reducing a signal level change. The liquid amplifier also has a high-order low-pass filter suitable for a low vortex frequency corresponding to a liquid flow rate having a small flow rate.

FIG. 2 shows the amplifier characteristics of the liquid amplifier 42 and the gas amplifier 31 during liquid measurement.
A (solid line) is the liquid amplifier characteristic, and B (dotted line) is the gas amplifier characteristic. Area of the shaded C not represent a liquid flow rate range Q _L, the liquid flow rate range Q _L, intended to be amplified to a level sufficient to flow pulse converter in the next stage of the trigger circuit 42 the vortex signal course , Liquid amplifier output A
_L (solid line) shows this and has a gain of 0 dB at the lower flow limit. However, gas amplifier output _BL (dotted line)
Is amplified to a level sufficient to output a flow rate pulse with the frequency of P _G as the lower limit.

FIG. 3 shows the amplifier characteristics of the liquid amplifier 42 and the gas amplifier 31 at the time of gas measurement.
Are amplifier characteristics common to FIG. The hatched area D indicates the gas flow rate range Q _{G. In} this range, the output B _G (dotted line) of the gas amplifier 31 has a sufficient gain and the vortex signal is output, but the liquid amplifier 41 output. A
_G (solid line) is not output. That is, at the time of liquid measurement, the liquid amplifier 41, the gas amplifier 31 and the trigger circuit 32,
A vortex signal of a sufficient level that triggers 42 is obtained and a flow rate pulse is output, but the gas amplifier 31 is used during gas measurement.
A sufficient level of the vortex signal for triggering the trigger circuit 32 can be obtained only from the above, but there is no output from the liquid amplifier 41.
The digital filters 33 and 43 output as a vortex signal of a noise component which is intermittently generated in a short time due to the fluctuation of the fluid, and also outputs a high level signal when the vortex signal is being output.

FIG. 4 is a block diagram showing the principle thereof, in which 11 is an input terminal, which is connected to the outputs of the trigger circuits 32 and 42.
12 is set to a count value that is slightly larger than the number of vortex signals of noise components that are expected to occur intermittently in the accumulation counter, and when the set value is reached, an overpulse is emitted and a flip-flop (FF) 14 is set. It has a terminal 12b for outputting a high level signal to be set and a reset terminal 12a. 13 is a timer which is set by an input signal, and when the set time is reached, the accumulation counter 12 and a flip-flop (FF)
A reset signal for resetting 14 is transmitted. The set time of the timer 13 is determined by the number of vortices per unit time of the lower limit flow rate in the normal flow rate and the frequency of the noise component. The operations of the digital filters 33 and 43 are performed as follows. Input signal is AND gate 15, accumulation counter 1
2 and the timer 13, and the accumulated counter 12 is integrated. When this signal is a noise vortex signal and does not reach the set value and a signal that continues even after the set time of the timer 13 has not been input, the timer 13 outputs a reset signal that resets the accumulation counter 12 and the FF 14. Therefore, the gate 15 remains closed and does not output to the output terminal 17. If the signal is normal and continues to be input, and the set value is reached within the set time of the timer 13, the overflow pulse becomes 12
The signal is output from terminal b, the FF 14 is set, the gate 15 is opened, and the signal is output from the terminal 17. On the other hand, a high level signal is output from the terminal 18, and the timer 13 is reset by the differentiating circuit 16, and the accumulation counter 1 is output from the timer 13.
2. A reset signal for resetting the FF 14 is output, but a normal vortex signal pulse continues to be output. The first AND gate 5, the second AND gate 6, the inverter 7, and the OR gate 8 are gate circuits that output the liquid vortex pulse when measuring the liquid flow rate and the gas flow pulse signal when measuring the gas flow rate by using the above-mentioned vortex signal characteristics. At the time of measuring the liquid flow rate, the high level (H) signal of the terminal 43a of the digital filter 43 (terminal 18 in FIG. 4) is input to the first AND gate 5 via the inverter 7 to output the gas converter 3 signal. By shutting off and directly connecting to the second AND gate 6, only the liquid flow rate pulse of the liquid converter 4 is output to the output terminal 9 via the OR gate 8. When measuring the gas flow rate, there is no output from the liquid converter 4, and therefore the terminal 4 of the digital filter 43
3a becomes low level (L), and the first
The AND gate 5 is opened to output a gas flow rate pulse signal,
Only the gas flow rate pulse is output from the terminal 9 via the OR gate 8. In the above description, the gate is opened and closed using the high (H) and low (L) level signals output from the terminal 18 of the digital filter in FIG.
Not limited to this, the fact that the liquid flow rate signal is output may be used.

Effect As described above, according to the vortex flowmeter converter of the present invention, even when liquid or gas flows through the same flow tube, the flow pulse signal of the liquid or gas is automatically discriminated and switched and output. There is no mistake, and simple instrumentation is possible without the complexity of switching gas and liquid converters at the same time as switching the flow path.

[Brief description of drawings]

FIG. 1 is a block diagram of circuit elements constituting the vortex flow rate converter of the present invention, FIG. 2 is an amplifier characteristic during liquid measurement, FIG. 3 is an amplifier characteristic during gas measurement, and FIG. The circuit block diagram of the digital filter employ | adopted for the structural circuit of a figure is shown. 1 ... Sensor, 2 ... Charge amplifier, 3 ... Gas converter, 4 ... Liquid converter, 5,6 ... And gate,
7 ... Inverter, 8 ... OR gate, 9 ... Output terminal.

Claims (1)

[Scope of utility model registration request] 1. A converter of a vortex flowmeter for measuring a fluid flow rate of either liquid or gas flowing in the same flow pipe, the converter comprising an amplifier circuit for amplifying a vortex signal and a low upper limit frequency. A liquid conversion circuit that converts a vortex signal in the liquid flow rate range with a liquid flow rate pulse and outputs a high level signal during conversion, and a gas conversion circuit that converts the vortex signal in the gas flow rate range with a high upper limit frequency into a gas flow rate pulse A conversion circuit and a conversion circuit for liquid and a conversion circuit for gas are respectively connected to the amplification circuit, and when measuring the liquid flow rate, the gas flow rate pulse output is closed by the high level signal, and only the liquid flow rate pulse signal is output. When measuring the flow rate, it consists of gate means that does not output the liquid flow rate pulse in the low frequency band but only the gas flow rate pulse in the high frequency band. Vortex flowmeter converter and outputs to determine the scan.