JPH0622173Y2 - Vortex flowmeter converter - Google Patents

Description

Description: TECHNICAL FIELD The present invention provides a liquid or gas flowing in the same flow tube, which has a fluid flow rate of either one of the flow rates when the gas is high-pressure, high-temperature vapor. The present invention relates to a converter for a vortex flowmeter, which has a function of discriminating one of a liquid and a gas conversion circuit mounted on another vortex flowmeter based on the state quantity of the fluid and switching the flow pulse of the 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 selects one of the state quantities of the vapor particularly when the gas is vapor having a temperature and pressure higher than that of the liquid. The purpose of the present invention is to provide a converter having a built-in switching means for detecting the difference between the state quantity of the vapor and the similar state quantity of the liquid and outputting only the flow rate signal. In the vortex flowmeter, a converter is used to amplify a vortex signal, a liquid conversion circuit for converting a vortex signal in the liquid flow rate range having a low upper limit frequency into a liquid flow rate pulse, and a gas having a high upper limit frequency. A gas conversion circuit for converting a vortex signal in a flow rate range into a gas flow rate pulse, a sensor for detecting a fluid state quantity, a comparator for transmitting a high level signal when the detection level of the sensor is equal to or lower than a set value, and a comparator for the comparator. A liquid conversion circuit and a gas conversion circuit connected to an amplifier circuit by a high level signal. A gate means for outputting only a liquid flow pulse, closing the gas flow pulse, and closing a low level liquid flow pulse to output a gas flow pulse. It is composed of and.

Embodiment FIG. 1 is a block diagram showing the structure of a vortex flowmeter converter of the present invention, in which 1 is arranged in a flow tube (not shown),
A sensor that detects a vortex signal in a vortex flowmeter that measures the flow rate of liquid or vapor, and the one shown in the figure is a piezoelectric element sensor that receives the vortex signal as fluctuating pressure and detects it as an electric signal.
The detection signal level is proportional to the piezoelectric coefficient, the density and the square of the flow rate. A charge amplifier 2 receives a high-impedance piezoelectric output signal from the sensor 1 and performs proportional amplification over a vortex frequency corresponding to a flow range of liquid to gas. Reference numeral 3 is a gas connected to the charge amplifier 2 and having a high upper limit frequency. A gas converter that outputs a vortex signal in the flow rate range as a gas flow rate pulse, and removes low- and high-frequency noise components included in the gas amplifier 31 and the approximate sine wave vortex signal output from the gas amplifier 31. It comprises a filter circuit 32 and a Schmitt circuit 33 which converts the sinusoidal eddy signal into a flow rate pulse. Reference numeral 4 denotes a liquid converter that is connected in parallel to the gas converter 3 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, and the liquid amplifier 41 and the liquid amplifier. It is composed of a filter circuit 42 for removing noise components in the low and high frequency regions included in the approximate sine wave vortex signal output from the amplifier 41, and a Schmitt circuit 43 for converting the sine wave vortex signal into a flow rate pulse. 10
Is a temperature sensor that measures the steam temperature and is attached to the flow tube near the vortex flowmeter. An amplifier 11 amplifies the output of the temperature sensor 10 and outputs a voltage proportional to the temperature.
A variable resistor 12 is connected to a DC power source (not shown) to set a reference temperature to be compared with the temperature output voltage of the amplifier 11. The reference temperature is set to an intermediate temperature between the liquid temperature and the vapor temperature. Reference numeral 13 is a comparator, which inputs the fluid temperature and the reference temperature to the input terminals 13a and 13b, respectively, and compares them.
It outputs a low level (“0”) when the fluid temperature is higher than the reference temperature, that is, a vapor flow, and outputs a high level (“1” when the fluid temperature is lower than the reference temperature, that is, a liquid flow. )) Is output. 5 and 6 are the first and second AND, respectively
A gate, 7 is an inverter, 8 is an OR gate, and 9 is an output terminal.

Next, the operation of the above circuit block diagram will be described.
The vortex signal output from the sensor 1 and amplified by the charge amplifier 2 is simultaneously input to the gas converter 3 and the liquid converter 4, and the gas amplifier 31 and the fluid amplifier 4 respectively.
It is amplified by 1.

When the gas is vapor, for example, saturated vapor of 5 atm is about 150 ° C. Therefore, the temperature of the volume 12 is set at 100 ° C., the liquid temperature is room temperature, and the liquid flows. Becomes a high level, the second AND gate 6 is opened and the liquid flow rate pulse is output from the OR gate 8 to the output terminal 9, but the flow rate pulse from the gas converter 3 is output by the inverted output of the inverter 7, Is closed and there is no output.
That is, due to the temperature difference between the vapor temperature and the liquid temperature, only the liquid flow rate pulse is output during liquid measurement, and during vapor measurement, the liquid flow rate signal is not output due to the frequency characteristic of the amplifier, and only the vapor flow rate pulse is output.

In the above, an example in which temperature is detected as the state quantity of gas has been described, but pressure may be used. In this case, the temperature sensor 10
Instead of this, a pressure sensor 10a (not shown) is provided.
As described above, when the liquid pressure is 2 to 3 atm and the vapor pressure is about 5 atm, the volume 12 is changed for setting the reference pressure, and the output of the comparator 13 is (the reference pressure is 4 atm).
Low level voltage for vapor and high level voltage for liquid. In the above description, the liquid pressure may be used as a reference, and even in this case, the comparator 1 may be used when measuring low-pressure liquid.
The output of 3 is selected high.

Effect As described above, according to the vortex flowmeter converter of the present invention, by automatically detecting the state quantities such as temperature and pressure of the gas or liquid flowing through the common flow pipe, the converter for gas or liquid can be automatically used. Since the converter can be switched to the converter for the corresponding fluid and the flow rate pulse can be output, it is possible to provide a simple vortex flowmeter that does not require special artificial switching of the converter circuit.

[Brief description of drawings]

FIG. 1 is a circuit block diagram of the vortex flowmeter converter of the present invention. 1 ... Sensor, 2 ... Charge amplifier, 3 ... Gas converter, 4 ... Liquid converter, 5,6 ... First and second ANs
D gate, 7 ... Inverter, 8 ... OR gate, 10
...... Temperature or pressure sensor, 13 ...... Comparator.

Claims (1)

[Scope of utility model registration request] 1. A vortex flowmeter converter for selectively measuring a flow rate of the liquid or gas, wherein the vortex flowmeter converter is provided in a flow tube through which a liquid or a gas having a state quantity different from the state quantity of the liquid flows. An amplification circuit for amplifying the vortex signal, a liquid conversion circuit connected to the amplification circuit for converting the vortex signal in the liquid flow rate range having a low upper limit frequency into a liquid flow rate pulse,
A gas conversion circuit connected to the amplification circuit for converting a vortex signal in a gas flow rate range having a high upper limit frequency into a gas flow rate pulse, a sensor for detecting a state quantity of a fluid flowing in the flow tube, and an output of the sensor It is composed of a comparator for comparing the level of either liquid or gas with a reference voltage and outputting it, and gate means for switching the liquid conversion circuit or the gas conversion circuit to output a flow rate pulse according to the output of the comparator. A vortex flowmeter converter characterized by.