SIGNAL PROCESSING METHOD, SIGNAL PROCESSING APPARATUS, AND CORIOLIS FLOWMETER
First Claim
1. A signal processing method for a Coriolis flowmeter in which at least one flow tube or a pair of flow tubes which is included in a measurement flow tube is alternately driven by causing a vibrator to be actuated by a driving device to vibrate the at least one flow tube or the pair of flow tubes, and at least one of a phase difference and a vibration frequency proportional to a Coriolis force acting on the at least one flow tube or the pair of flow tubes is detected by two velocity sensors or acceleration sensors which are vibration detection sensors, to thereby obtain at least one of a mass flow rate and a density of a fluid to be measured,the signal processing method comprising:
- performing frequency conversion to combine, based on an arbitrary oscillation frequency, each of two flow rate signals obtained by A/D conversion on input signals of the vibration frequency proportional to the Coriolis force acting on the at least one flow tube or the pair of flow tubes, which are detected by the two velocity sensors or acceleration sensors, to obtain a composite frequency signal;
measuring a frequency of the composite frequency signal associated with at least one of the two velocity sensors or acceleration sensors;
transmitting a control signal based on the measured frequency;
controlling a frequency of a sum or difference frequency component of the composite frequency signal to a constant value;
obtaining a resonance frequency of the at least one flow tube or the pair of flow tubes based on the control signal, calculating the density of the fluid to be measured based on the control signal; and
measuring a phase from the sum or difference frequency component of the composite frequency signal having the controlled frequency.
1 Assignment
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Accused Products
Abstract
[Object] To provide a signal processing apparatus with which, even when a temperature of a fluid to be measured changes, even when air bubbles are mixed into the fluid, to be measured, or even when the fluid to be measured rapidly changes from gas to liquid, measurement may be always performed with constant precision and phase and density measurements may be performed with a small computing amount.
[Solving Means] A signal processing apparatus for a Coriolis flowmeter in which at least one flow tube or a pair of flow tubes which is included in a measurement flow tube is alternately driven by causing a vibrator to be actuated by a driving device to vibrate the at least one flow tube or the pair of flow tubes, and at least one of a phase difference and a vibration frequency proportional to a Coriolis force acting on the at least one flow tube or the pair of flow tubes is detected by a velocity sensor or acceleration sensor which is a vibration detection sensor, to thereby obtain at least one of a mass flow rate and a density of a fluid to be measured, includes: a transmitter (90) for transmitting a frequency signal which is modulatable; and a frequency conversion section (85) for performing frequency conversion to add (or subtract) an output frequency FX from the transmitter (90) to (or from) an input frequency detected by the velocity sensor or acceleration sensor and shifting a frequency value obtained by the frequency conversion to a constant value.
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Citations
17 Claims
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1. A signal processing method for a Coriolis flowmeter in which at least one flow tube or a pair of flow tubes which is included in a measurement flow tube is alternately driven by causing a vibrator to be actuated by a driving device to vibrate the at least one flow tube or the pair of flow tubes, and at least one of a phase difference and a vibration frequency proportional to a Coriolis force acting on the at least one flow tube or the pair of flow tubes is detected by two velocity sensors or acceleration sensors which are vibration detection sensors, to thereby obtain at least one of a mass flow rate and a density of a fluid to be measured,
the signal processing method comprising: -
performing frequency conversion to combine, based on an arbitrary oscillation frequency, each of two flow rate signals obtained by A/D conversion on input signals of the vibration frequency proportional to the Coriolis force acting on the at least one flow tube or the pair of flow tubes, which are detected by the two velocity sensors or acceleration sensors, to obtain a composite frequency signal; measuring a frequency of the composite frequency signal associated with at least one of the two velocity sensors or acceleration sensors; transmitting a control signal based on the measured frequency; controlling a frequency of a sum or difference frequency component of the composite frequency signal to a constant value; obtaining a resonance frequency of the at least one flow tube or the pair of flow tubes based on the control signal, calculating the density of the fluid to be measured based on the control signal; and measuring a phase from the sum or difference frequency component of the composite frequency signal having the controlled frequency. - View Dependent Claims (2, 3, 4)
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5. A signal processing apparatus for a Coriolis flowmeter in which at least one flow tube or a pair of flow tubes which is included in a measurement flow tube is alternately driven by causing a vibrator to be actuated by a driving device to vibrate the at least one flow tube or the pair of flow tubes, and at least one of a phase difference and a vibration frequency proportional to a Coriolis force acting on the at least one flow tube or the pair of flow tubes is detected by a velocity sensor or acceleration sensor which is a vibration detection sensor, to thereby obtain at least one of a mass flow rate and a density of a fluid to be measured,
the signal processing apparatus comprising: -
a transmitter for transmitting a frequency signal which is modulatable; and a frequency conversion section for performing frequency conversion to add (or subtract) an output frequency FX from the transmitter to (or from) an input frequency detected by the velocity sensor or acceleration sensor and shifting a frequency value obtained by the frequency conversion to a constant value. - View Dependent Claims (8, 9)
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6. A signal processing apparatus for a Coriolis flowmeter in which at least one flow tube or a pair of flow tubes which is included in a measurement flow tube is alternately driven by causing a vibrator to be actuated by a driving device to vibrate the at least one flow tube or the pair of flow tubes, and at least one of a phase difference and a vibration frequency proportional to a Coriolis force acting on the at least one flow tube or the pair of flow tubes is detected by a pair of velocity sensors or acceleration sensors which are a pair of vibration detection sensors, to thereby obtain at least one of a mass flow rate and a density of a fluid to be measured,
the signal processing apparatus comprising: -
a transmitter for transmitting a frequency signal which is modulatable; a first frequency conversion section for performing frequency conversion to add (or subtract) an output frequency from the transmitter to (or from) an input signal frequency obtained by converting a signal of one of the pair of vibration detection sensors into a digital signal by a first A/D converter, to adjust a frequency value obtained by the frequency conversion to a constant value; and a second frequency conversion section for performing frequency conversion to add (or subtract) the output frequency from the transmitter to (or from) an input signal frequency obtained by converting a signal of another one of the pair of vibration detection sensors into a digital signal by a second A/D converter, to adjust a frequency value obtained by the frequency conversion to a constant value. - View Dependent Claims (14, 16)
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7. A signal processing apparatus for a Coriolis flowmeter in which at least one flow tube or a pair of flow tubes which is included in a measurement flow tube is alternately driven by causing a vibrator to be actuated by a driving device to vibrate the at least one flow tube or the pair of flow tubes, and at least one of a phase difference and a vibration frequency proportional to a Coriolis force acting on the at least one flow tube or the pair of flow tubes is detected by a pair of vibration detection sensors, to thereby obtain at least one of a mass flow rate and a density of a fluid to be measured,
the signal processing apparatus comprising: -
a transmitter for transmitting a frequency signal which is modulatable; a first frequency conversion section for shifting in frequency, to a constant frequency signal, an input signal frequency obtained by converting a signal of one velocity sensor of the pair of vibration detection sensors into a digital signal by a first A/D converter, based on an output frequency from the transmitter to move the input signal frequency to another frequency band; a second frequency conversion section for shifting in frequency, to a constant frequency signal, an input signal frequency obtained by converting a signal of another velocity sensor of the pair of vibration detection sensors into a digital signal by a second A/D converter, based on the output frequency from the transmitter to move the input signal frequency to another frequency band; and a frequency measurement section for measuring a frequency of a first frequency signal, which is obtained as the constant frequency signal through the shifting by and output from the first frequency conversion section, and outputting the measured frequency of the first frequency signal to the transmitter to control, based on the frequency after the shifting by the first frequency conversion section, output frequencies from the first frequency conversion section and the second frequency conversion section so that the input signal frequency obtained by converting the signal of the one velocity sensor of the pair of vibration detection sensors into the digital signal by the first A/D converter is a desired frequency. - View Dependent Claims (10, 11, 12, 15, 17)
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13. A Coriolis flowmeter in which at least one flow tube or a pair of flow tubes which is included in a measurement flow tube is alternately driven by causing a vibrator to be actuated by a driving device to vibrate the at least one flow tube or the pair of flow tubes, and at least one of a phase difference and a vibration frequency proportional to a Coriolis force acting on the at least one flow tube or the pair of flow tubes is detected by a pair of velocity sensors or acceleration sensors which are a pair of vibration detection sensors, to thereby obtain at least one of a mass flow rate and a density of a fluid to be measured,
the Coriolis flowmeter comprising: -
a transmitter for transmitting a frequency signal which is modulatable; a first frequency conversion section for shifting in frequency, to a constant frequency signal, an input signal frequency θ
obtained by converting a signal of one velocity sensor of the pair of vibration detection sensors into a digital signal by a first A/D converter, based on an output frequency θ
Xn from the transmitter to move the input signal frequency to a desired frequency band;a second frequency conversion section for shifting in frequency, to a constant frequency signal, an input signal frequency θ
obtained by converting a signal of another velocity sensor of the pair of vibration detection sensors into a digital signal by a second A/D converter, based on the output frequency θ
Xn from the transmitter to move the input signal frequency to a desired frequency band; anda frequency measurement section for measuring a frequency of a first frequency signal, which is obtained as the constant frequency signal through the shifting by and output from the first frequency conversion section, and outputting the measured frequency of the first frequency signal to the transmitter to control the output frequency so that the frequency after shifting by each of the first frequency conversion section and the second frequency conversion section is a desired frequency.
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Specification