JPH0648350Y2 - Vortex flowmeter converter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a two-wire analog signal of the same span, which is selected by switching pulse signals of different repetition frequencies corresponding to vortices in a vortex flowmeter for measuring liquid or gas by a command signal. A vortex flowmeter converter for transmitting.

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. Flow rate information such as integrated flow rate and / or instantaneous flow rate is also required in the vortex flowmeter, but these flow rate information is transmitted from the converter integrally mounted on the vortex flowmeter to a receiver provided in a remote place by two-wire transmission. In many cases, it is processed on the receiver side. In this method, a power supply and a load resistance are arranged on the receiver side, and the circuit impedance of the output circuit on the converter side is changed according to the flow rate signal, whereby flow rate information is obtained as a change in the current flowing through the load resistance. . When the flow rate information is an instantaneous flow rate, the flow rate pulse output corresponding to the vortex signal that changes according to the flow rate in the converter is shaped into a flow rate with a constant crest value and a constant pulse width, and then integrated. It is converted to a signal and input to the output circuit. As mentioned above, when measuring the flow rate of liquid or gas with the same pipe, the upper limit frequency of the vortex signal with liquid or gas is different, so that the flow signal of liquid and gas should have the same signal level on the receiver side. As a means to do so, the span adjustment of the converter, that is, the pulse width of the flow rate pulse is adjusted every time liquid and gas are introduced.

Problems of Conventional Technology In the above-mentioned conventional technology, there is a complexity that requires adjustment of the converter every time a liquid or gas flows in, and in particular, in the case of vapor cleaning after measuring the liquid, time adjustment is required. In reality, it is impossible to make adjustments as there is no room. Further, the liquid measurement period was performed for a long period of time, and it was applicable only when the period for measuring the gas flow rate was long enough.

Means for Solving Problems The vortex flowmeter converter of the present invention has been made in view of the above problems, and a pulse converter for liquid or gas can be easily provided by a flow rate switching signal of liquid or gas. The span is accurately adjusted by switching the mono multivibrator) and adjusting the pulse width in advance in many pulse converters. That is, the gist of the present invention is to provide a first and second monostable multivibrator which inputs a pulse signal corresponding to a vortex generated according to a flow rate and outputs different pulse widths at a constant peak value, A gate circuit that selects and outputs one of the outputs of the monostable multivibrator according to a selection signal, a D / A conversion circuit that converts the output of the gate circuit into an analog signal, and an output of the D / A conversion circuit Is an eddy flowmeter converter configured with an output circuit for transmitting two lines.

Embodiment FIG. 1 is a circuit block diagram showing an outline of the vortex flowmeter converter of the present invention. In the drawing, reference numeral 1 is a vortex flowmeter (not shown) after amplifying a vortex signal output according to vortex fluctuation, It is an input terminal for inputting a flow rate pulse of a Schmitt circuit for pulse-converting an approximate sine wave vortex signal output from the filter circuit through a filter circuit for removing low-frequency and high-frequency noise components outside the flow rate range. There are liquid and gas signals in the flow pulse. Reference numerals 3 and 4 are well-known first and second monostable multivibrators (hereinafter referred to as mono-multi) provided with adjusting resistors VR ₁ and VR ₂ for adjusting pulse widths for gas and liquid, respectively. Reference numeral 2 denotes a switching signal output from a signal generator (not shown) for selectively outputting either the gas mono-multi or the liquid mono-multi signal, and a high-level signal ("1") or a low signal at the terminal. Level signal (“0”)
Is supplied. Reference numeral 5 is a first AND gate, which uses the signal of the gas multi-multi 3 and the inverted signal of the switching signal 2 by the inverter 7 as input signals. Reference numeral 6 is a second AND gate, which uses the signal of the liquid mono-multi 4 and the switching signal 2 as input signals. Reference numeral 8 is an OR gate that outputs a signal of either the first or second AND gate 5 or 6, and 9 is an integrating circuit that converts the flow rate pulse of the OR gate 8 into an analog signal.
It is shown with R ₁ and capacitor C ₁ . Reference numeral 10 is a signal amplifier circuit to which an integrated signal is input via the input resistor R ₂ . VR ₃ is a variable resistor for zero adjustment, and R ₃ is a feedback resistor. 11 is an output circuit,
The output signal from the signal amplifying circuit 10 is impedance-converted and transmitted from the terminals 12 and 13 to a receiving circuit (not shown) by two lines. As mentioned above, the receiving circuit consists of a series circuit of a DC power supply and a load resistance, and the positive side of the DC power supply is the terminal 12 and the load resistance is the terminal.
Connected to 13. R ₄ is a signal detection resistor and is connected to the feedback resistor R ₃ . As the vortex signal of the vortex flowmeter, a system of detecting vortex fluctuation pressure or lift is often used, and the signal level of this signal is proportional to the fluid density and the square of the flow velocity. Generally, in industrial use, the upper limit flow velocity for liquid flow rate measurement is much smaller than the upper limit flow velocity for gas. However, as described above, since the Strouhal number is substantially constant within the measurable Reynolds number range, the vortex frequency in the gas flow rate range is much higher than the vortex frequency in the liquid flow rate range. Therefore, the number of repetitions of the input pulse to the first mono-multi 3 is much larger than the number of repetitions of the input pulse to the second mono-multi 4. Therefore, the output pulse width of the first mono-multi 3 is adjusted small, and the pulse width of the output pulse of the second mono-multi vibrator 4 is adjusted large. The adjustment is performed by rotating the variable resistors VR ₁ and VR ₂ . In the flow rate range, the vortex frequency, that is, the number of repetitions of the flow rate pulse is known, so that the output voltages of the integrating circuit 9 are adjusted to be equal to each other, and the signal level at this time becomes a value determined by the receiving circuit. Is decided. Switching of the output of the first mono-multi 3 at the time of gas measurement or the output of the second mono-multi 4 at the time of liquid measurement is performed by the switching signal applied to the terminal 1, but when the switching signal is at the high level "1", the inverter 7 The first gate 5 is closed by the inversion output of, and the liquid flow pulse is output from the OR gate 8 by opening the second gate 6, and when the switching signal is at the low level "0", When the first gate 5 is opened and the second gate 6 is closed, a gas flow rate pulse is output from the OR gate 8. The flow rate pulse of the liquid flow rate or the gas flow rate is selected according to the signal level of the switching signal, and the terminals 12 and 13 are connected. The instantaneous flow rate signal of the corresponding fluid is transmitted via two lines via the same.

Effect As described above, according to the vortex flowmeter converter of the present invention, the first mono-multi switch that outputs the pre-adjusted pulse width by transmitting the switching signal output according to the flow rate measurement of the liquid or gas. Alternatively, since the instantaneous flow rate as an analog signal can be transmitted by two lines by switching the second mono-multi, the flow rate can be measured with an extremely simple and inexpensive circuit configuration.

[Brief description of drawings]

FIG. 1 is a circuit block diagram of the vortex signal converter of the present invention. 1 ... Flow rate pulse input terminal, 2 ... Switching signal terminal of fluid to be measured,
3, 4 ... First and second mono-multis for gas and liquid,
5, 6 ... AND gate, 7 ... Inverter, 8 ... OR gate, 9 ... Integration circuit, 10 ... Signal amplification circuit, 11 ... Output circuit.

Claims (2)

[Scope of utility model registration request] 1. An input terminal to which a pulse signal corresponding to a vortex signal having a frequency proportional to the flow rate of gas or liquid having a different flow rate range is input, and an input terminal connected to the input terminal and adapted to the pulse signal frequency of the gas. A first monostable multivibrator having an adjustable pulse width and outputting a gas pulse signal of a constant crest value, and a second monostable multivibrator having an adjustable pulse width and outputting a liquid pulse signal of a constant crest value Monostable multivibrator, and first and second ANDs to which outputs of the first and second monostable multivibrators and a switching signal for instructing whether to input the gas pulse signal or the liquid pulse signal are input. A gate, an integration circuit for converting either the switched gas pulse or liquid pulse into an analog signal proportional to the pulse frequency, and the converted analog signal to 2 A signal amplification and output circuit for line transmission, adjusting the pulse widths of the gas pulse signal and the liquid pulse signal, and converting into a constant level analog signal in the flow range of the gas or liquid. And vortex flowmeter converter. 2. The pulse width of the gas or liquid pulse signal output from the first and second monostable multivibrators is determined by the repetition frequency of each pulse signal, and the outputs of the integrating circuits are made equal. The vortex flowmeter converter according to claim 1, wherein: