JPH0626813Y2 - Vortex flowmeter circuit - Google Patents

Description

TECHNICAL FIELD The present invention comprises a vortex flowmeter converter for transmitting a vortex signal in two lines and a receiver for receiving the vortex signal. The flow rate of gas or liquid is switched by switching the receiver side. The present invention relates to a vortex flowmeter circuit that enables measurement.

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, it is necessary to prepare a plurality of converters having characteristics applicable to liquids and gases, and further in the case of 2-wire transmission, a signal switching means is further required. It has to be provided separately, and there is a problem that it is not only expensive but also large in size.

Means for Solving Problems The present invention has been made in view of the above-mentioned problems, and two-wire transmission is performed with a common converter, and liquid or gas flow rate measurement is switched on the receiver side, and operation is performed by the switching. By operating the switch that can switch the circuit constant of the circuit element of the converter by the photodiode of the diode bridge
Specifically, an amplification circuit that variably amplifies the approximate sine wave vortex signal output from the vortex sensor in the flow rate range band, a low-pass filter circuit of the vortex signal frequency, and a pulse conversion circuit that converts the vortex signal into a pulse signal. A conversion circuit for converting the pulse signal into a flow rate signal, and a first circuit for transmitting the flow rate signal by two wires,
A converter including an output circuit having a second terminal, and third and fourth terminals connected to the first and second terminals, and the third and fourth terminals.
In a vortex flowmeter circuit composed of a DC power supply connected in series with a fourth terminal and a receiver composed of a load resistance, the receiver side has a series circuit of a DC power supply and a load resistance with polarities of the third and fourth terminals. , The converter side is provided with a diode bridge that supplies forward power to the output circuit regardless of the polarity of the first and second terminals, and the converter side is turned on by any switching. And a converter having characteristics corresponding to liquid and gas flow rate measurement by switching the gain of the amplifier circuit and the filter constant in the filter circuit by a switch that operates in response to the light emission of the light emitting diode. A vortex flowmeter circuit is provided.

Embodiment FIG. 1 is a block diagram of a vortex flowmeter circuit of the present invention. In the drawing, reference numeral 1 is a vortex sensor, which is inserted in a flow pipe (not shown) and measures the flow rate of liquid or gas. The piezoelectric element sensor which is built in the meter and detects the vortex fluctuating pressure as an electric signal is shown. 2 is an amplification circuit for amplifying a vortex signal of vortex sensor 1, a charge amplifier with high input impedance, the light of the feedback resistor R ₁ and the feedback resistor R ₁ and the photosensitive switch P ₃ in 21 indicated by a dotted line Closed by input, feedback resistor R ₁
It has a variable amplification function by a resistor R ₂ connected in parallel with. Reference numeral 3 denotes a filter circuit, which is a combination of a low-pass filter and a high-pass filter having high-order damping characteristics for vortex signals outside the flow rate range, or a tracking filter which tracks vortex frequency fluctuations with the vortex frequency as the central frequency Reference numeral 31 denotes a capacitor which is a circuit element of the filter circuit 3, and for example, a capacitor C
₁ and a capacitor C ₂ which is closed by the light input of the photosensitive switch P _{4 and} is connected in parallel with the capacitor C ₁ to change the attenuation characteristic. Reference numeral 4 is a Schmitt circuit which converts an approximate sine wave eddy signal of a predetermined level or higher output from the filter circuit 3 into a flow rate pulse. 5 is an arithmetic unit for converting the flow rate pulse into a unit flow rate pulse or analog conversion to flow rate information such as instantaneous flow rate, 6 is an output circuit for transmitting the signal of the arithmetic unit 5 by two lines, and 9 is a power source of the output circuit 6. , 11 are load resistances. 7 is a diode bridge, which is a diode D
₁ , D ₂ and light emitting diodes D ₃ and D ₄ , and the positive output terminal 71 is connected to the high potential side 61 of the output circuit 6 and the negative output terminal 7
2 is connected to the low potential side 62. Vortex sensor 1,
The amplifier 2, the filter circuit 3, the Schmitt circuit 4, the arithmetic circuit 5, the output circuit 6, and the diode bridge 7 are the converter A mounted on the vortex flowmeter (not shown), and the power source 9 and the load resistor 11 are two wires. It constitutes the receiver B to be transmitted. Between the converter A and the receiver B, a first terminal T ₁ of the converter, a third terminal T ₃ of the receiver side, a second terminal T ₂ of the converter and a fourth terminal T ₄ of the receiver side are provided. And are connected by transmission lines (shown by dotted lines). 8 is a changeover switch on the receiver side, which is composed of a pair of switches 81 and 82 for switching the polarity of the series circuit of the power source 9 and the load resistor 11 at the third and fourth terminals. In the block diagram shown in Figure 1 on ordination, the changeover switch 8, in which the measurement fluid by switching to select whether a liquid or gas, switches 81 and 82 shown are each S ₁ -1, S ₂ This is a case where the gas flow rate is measured when -1 is closed, and a voltage is applied to the output circuit 6 through the fourth terminal T ₄ , the second terminal T ₂ , and the diode D ₁ , and the diode D ₂ , The first terminal T ₁ ,
Return to the load resistance 11 via the third terminal T ₃ . In this case, the photosensitive switches P ₃ and P ₄ remain open without being responded, and therefore the feedback resistance of the amplifier 2 is only R ₁ and the gain characteristic suitable for the gas flow rate range is the feedback resistance R 1.
Determined by ₁ . Also in the case of the filter circuit 3, C ₁ is selected as the capacitor capacity. The eddy signal has a level proportional to the fluid density and the square of the flow velocity. In the case of gas, the density is small and the flow velocity is large, so the amplifier gain is increased in the small flow region and the third-order low-pass filter is used in the large flow region. It is used to equalize the vortex signal level and to sufficiently attenuate outside the flow rate range to improve the S / N. On the other hand, in the case of liquid, since the density is high and the flow velocity is low, the amplifier gain is made small in the small basin, and the secondary to the third in the large basin.
The following low pass filter is used. Then, when switching the changeover switch 81, 82 to S ₁ -2, S ₂ -2, a case of measuring the liquid flow rate, a third terminal T ₃ to the output circuit 6, the first terminal T _1, A voltage is applied via the light emitting diode D ₃ and returns to the load resistor 11 via the light emitting diode D ₄ and the second terminal T ₂ . From these, the light emitting diode D ₃ ,
D ₄ emits light, and in response to this, light sensitive switches P ₃ and P ₄
Is closed, and the resistors R ₁ and R ₂ are connected in parallel on the amplifier 2 side to reduce the amplifier gain. In the filter circuit 3, the capacitors C ₁ and C ₂ are connected in parallel, and the cutoff frequency suitable for the liquid flow rate is reduced. The characteristics are obtained. Although the light emitting diodes D ₃ and D ₄ are shown in the figure, the number of these light emitting diodes is not limited to one, and a plurality of light emitting diodes may be arranged in parallel, and one of the light emitting diodes D ₃ and D ₄ is a normal diode. Instead of using either the diode D ₁ or D ₂ as a light emitting diode, the circuit element of the amplifier 2 or the filter circuit 3 may be selected according to the circuit characteristics. The point is that the changeover switch 8 on the receiver B side is switched. It suffices to be able to switch the light sensitive switches P ₃ , P ₄ or other light sensitive switches (not shown) that have the characteristics of the amplifier 1 and the band characteristic of the filter circuit 2 which are suitable for the liquid flow rate or the gas flow rate.

Effect As described above, according to the vortex flowmeter circuit of the present invention, in the two-wire transmission system of the vortex signal, the photodiode of the diode bridge provided on the converter side is made to emit light by switching the changeover switch on the receiver side. By the remote switching means of activating an optical switch sensitive to the light emission of the light emitting diode, the circuit element of one conversion circuit can be used for liquid or gas flow rate measurement without the need for two conversion circuits for liquid and gas. It is possible to provide a simple and compact two-wire transmission type vortex flowmeter circuit because it is possible to switch to a suitable characteristic.

[Brief description of drawings]

FIG. 1 is a block diagram showing the principle of the vortex flowmeter circuit of the present invention. 1 ... Vortex sensor, 2 ... Amplifier, 3 ... Filter circuit,
4 ... Schmidt circuit, 5 ... arithmetic circuit, 6 ... output circuit, 7 ... diode bridge, 8 ... changeover switch,
9 ...... power, 11 ...... load resistor, D _3, D ₄ ...... emitting diodes, P _3, P ₄ ...... photoresponsive switch.

Claims (1)

[Scope of utility model registration request] 1. An amplification circuit for variably amplifying an approximate sine wave vortex signal output from a vortex sensor in a band of a flow rate range, a low-pass filter circuit for a vortex signal frequency, and a pulse conversion circuit for converting the vortex signal into a pulse signal. A conversion circuit for converting the pulse signal into a flow rate signal, and a first circuit for transmitting the flow rate signal by two wires,
A converter including an output circuit having a second terminal, and third and fourth terminals connected to the first and second terminals, and the third and fourth terminals.
In a vortex flowmeter circuit composed of a DC power supply connected in series with a fourth terminal and a receiver composed of a load resistance, the receiver side has a series circuit of a DC power supply and a load resistance with polarities of the third and fourth terminals. , The converter side is provided with a diode bridge that supplies forward power to the output circuit regardless of the polarities of the first and second terminals, and the converter side can be switched by either. A converter having a characteristic that corresponds to liquid and gas flow rate measurement by switching the conducting diode to a light emitting diode, and switching the gain of the amplifier circuit and the filter constant in the filter circuit by a switch that operates according to the light emission of the light emitting diode. A vortex flowmeter circuit characterized by: