JP2016128794A - Physical quantity measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a physical quantity measurement device capable of continuously measuring a desired physical quantity such as viscosity of liquid, in a state in which the environmental resistance is high, the device is stable for a long term, and the influence of temperature variation is small.SOLUTION: The physical quantity measurement device measures a desired physical quantity on the basis of the resonance frequency of a sensor. The physical quantity measurement device includes: a first phase synchronization loop including the sensor; a second phase synchronization loop including the sensor; and an adder for adding an output signal of a voltage-control-type oscillator of the first phase synchronization loop to an output signal of a voltage-control-type oscillator of the second phase synchronization loop. The two phase synchronization loops are operated in parallel.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a physical quantity measuring apparatus, and more particularly to an improvement in a signal processing circuit in a physical quantity measuring apparatus configured to measure a desired physical quantity based on a half-value width of a resonance frequency of a sensor.

  One type of physical quantity measuring device configured to measure a desired physical quantity based on the half-value width of the resonance frequency of the sensor is a vibration viscometer.

Japanese Industrial Standard (JIS) 8803: 2011 defines “Method for measuring viscosity of liquid”, and item 11 describes “Method for measuring viscosity with vibration viscometer”.
1) Features and measurement principles 2) Types of vibration viscometers 3) Auxiliary tools used for measurement 4) Operation 5) Correction The details are explained in detail for each item.

FIG. 3 is a principle configuration diagram of a vibration type viscometer described in the above JIS, and shows a viscometer based on rotational vibration (twist).
The viscometer shown in FIG. 3 is a method for obtaining a viscous resistance by resonating a cylindrical vibrator in the rotation direction, and has a resonance structure in which the cylindrical viscosity detection unit vibrates in the rotation direction.

  In FIG. 3, a torsion spring 3 is inserted into a container 2 filled with a sample 1, and an inertial mass 4 is attached to the end thereof. A node 5 is formed in the middle portion of the torsion spring 3 inside the container 2.

  An inertial mass 7 is attached to the other end of the torsion spring 3 via a drive unit 6. An accelerometer 8 is attached to the upper part of the inertial mass 7.

  In such a configuration, the drive unit 6 rotationally drives the torsion spring 3 to which the inertia masses 4 and 7 are attached at both ends to the left and right.

  The inertial mass 4 provided inside the container 2 acts so that the viscous resistance corresponding to the viscosity of the sample 1 hinders the rotation operation, but the inertial mass 7 provided outside the container 2 has an air resistance. Only acts and air resistance is virtually negligible.

  As a result, rotational vibration (twist) related to the viscosity of the sample 1 is generated in the torsion spring 3, and the accelerometer 8 measures the acceleration of the inertial mass 7 provided in the upper part, Information related to the viscosity of sample 1 can be determined.

JP-A-11-183353

  Patent Document 1 discloses a method and apparatus configuration for continuously and highly accurately measuring fuel viscosity.

FIG. 4 is a circuit diagram of the liquid viscosity measuring apparatus described in Patent Document 1, and the reference numerals are appropriately changed from those described in Patent Document 1. The liquid viscosity measuring apparatus shown in FIG. 4 includes an oscillator 10 having an input terminal 10a and an output terminal 10b each composed of electrodes, an oscillator 11 that applies an oscillating voltage to the input terminal 10a of the oscillator 10, and an oscillator 10 A frequency measurement circuit 12 that detects a resonance frequency f ₀ of an oscillating voltage applied to the input terminal 10a, a density calculation circuit 13 that detects the density ρ of the fuel liquid from the resonance frequency f ₀ detected by the frequency measurement circuit 12, and an oscillation An electrical output measurement circuit 14 that measures the electrical output from the output terminal 10b constituted by the electrodes of the apparatus 10, and a product value computation circuit that computes the product ξ of the density ρ and the viscosity η of the fuel liquid from the electrical output measurement circuit 14 15 and a viscosity calculation circuit 16 for calculating the viscosity η of the fuel liquid from the outputs of the density calculation circuit 13 and the product value calculation circuit 15. As the oscillator 11, a pulse generator or an AC power supply is used.

  In the circuit configuration of FIG. 4, the viscosity is measured from the relationship between the frequency of the oscillator 11, the input A and output B of the vibrator 10, and the frequency.

  However, according to the configuration of FIG. 4, the frequency of the oscillator 11 also changes due to a temperature change. Therefore, it is necessary to devise so that the viscosity measurement is not affected by the temperature change.

  FIG. 5 is a circuit diagram of another conventional liquid viscosity measuring device, which measures the viscosity based on the Q of the circuit.

  In FIG. 5, the output of a voltage controlled oscillator (hereinafter also referred to as VCO) 1 is input as a drive signal to a viscometer sensor 3 via an amplifier 2. The output signal of the viscometer sensor 3 is input to the phase detector 6 via the amplifier 4. The output signal of the VCO 1 is also input to the phase detector 6 via the phase shifter 5. The output signal of the phase detector 6 is fed back to the VCO 1 via the integrator 7.

  In the circuit configuration of FIG. 5, a phase-locked loop (hereinafter also referred to as PLL) including the viscometer sensor 3 is formed.

  When the viscometer sensor 3 performs a general resonance operation, the input / output signal ratio is maximized at the resonance point, and the phase between the input and output is shifted by −90 °.

  Here, when the phase shift amount of the phase shifter 5 is set to zero, the output of the phase detector 6 has a phase difference of −90 ° between the output of the amplifier 4 and the output of the phase shifter 5, so that at the resonance point. Continues the oscillation operation.

  When the phase shift amount of the phase shifter 5 is −45 °, the phase between the input and output becomes 135 °. When the phase shift amount is + 45 °, the phase between the input and output becomes −45 °, and the half width is measured. Two frequencies can be obtained and Q can be measured.

  Various methods of viscosity measurement are performed by measuring the phase difference between AB based on the signal level and frequency of the input signal A of the viscometer sensor 3 and the signal level and frequency of the output signal B of the viscometer sensor 3. it can.

  By the way, the Q value of the vibrator 10 in FIG. 4 and the Q value in the circuit configuration of FIG. 5 can be obtained in principle by measuring the resonance behavior in the vicinity of the resonance point. In measurement, a plurality of measurement sequences are assembled, and the viscosity is obtained from the measurement results and prior calibration information.

  However, when continuous measurement values are required for measuring the viscosity of a measurement target, it is difficult to realize continuous measurement by viscosity measurement according to the principle of the conventional example.

  Therefore, as a countermeasure, for example, it has been proposed to perform a number of measurements in advance calibration and perform calibration calculation from the measurement results.

  However, when measuring the viscosity of a liquid, the change in the viscosity of the liquid itself of the object due to temperature is large. Therefore, in order to appropriately determine the characteristics of the sensor, it is necessary to perform a large number of calibration measurements and accumulate a large amount of data. is there.

  Furthermore, when severe environmental resistance such as high temperature and high pressure is required, it is not possible to use a sensor designed for use in a place where the temperature change of the environment is small, A more complicated calibration process is required.

  The present invention pays attention to such conventional problems, and its purpose is to have high environmental resistance, stable over a long period of time, and less affected by temperature changes, such as the viscosity of a liquid. An object of the present invention is to provide a physical quantity measuring apparatus capable of continuously measuring a desired physical quantity.

The invention of claim 1 which achieves such a problem,
In a physical quantity measuring device configured to measure a desired physical quantity based on the resonance frequency of the sensor,
A first phase-locked loop including the sensor;
A second phase-locked loop including the sensor;
An adder for adding the output signal of the voltage controlled oscillator of the first phase locked loop and the output signal of the voltage controlled oscillator of the second phase locked loop;
And the two phase-locked loops are operated in parallel.

The invention of claim 2 is the physical quantity measuring device of claim 1,
Q is measured by setting the phase shift amount of the one phase locked loop to + 45 ° and the phase shift amount of the other phase locked loop to −45 °.

The invention of claim 3
In a physical quantity measuring device configured to measure a desired physical quantity based on the resonance frequency of the sensor,
A first phase-locked loop including the sensor;
A second phase-locked loop including the sensor;
An adder for adding the output signal of the voltage controlled oscillator of the first phase locked loop and the output signal of the voltage controlled oscillator of the second phase locked loop;
A multiplier for multiplying the output signals of the two phase-locked loops;
A low-pass filter that extracts a frequency component of the difference from the output signal of the multiplier;
The frequency component of the difference for measuring Q is continuously obtained.

The invention of claim 4 is the physical quantity measuring device according to claim 2 or 3, wherein
The desired physical quantity is a viscosity.

  According to these configurations, it is possible to realize a physical quantity measuring apparatus that can measure a desired physical quantity in a state that is stable for a long time and is less affected by temperature changes.

It is a block diagram which shows one Example of the vibration-type viscometer based on this invention. It is a block diagram which shows the other Example of the vibration type viscometer based on this invention. It is a principle block diagram of the vibration type viscometer described in JIS. It is a circuit example figure of the other conventional liquid viscosity measuring apparatus. It is a circuit example figure of the other conventional liquid viscosity measuring apparatus.

  Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a vibratory viscometer according to the present invention, and the same reference numerals are given to the parts common to FIG. In FIG. 1, when the PLL in FIG. 4 is a first PLL, in addition to the first PLL, a second circuit composed of a VCO 8, a phase shifter 9, a phase detector 10, and an integrator 11 is further provided. A PLL is provided.

  In order to operate the first PLL and the second PLL in parallel, the output signal of the VCO 1 constituting the first PLL and the second signal are connected between the VCO 1 constituting the first PLL and the amplifier 2. An adder 12 is provided for adding the output signals of the VCO 8 constituting the PLL.

  In such a configuration, the output signal of the VCO 1 constituting the first PLL and the output signal of the VCO 8 constituting the second PLL are added to the viscometer sensor 3 by the adder 12 and input. Since phase detection is performed by the phase detectors 6 and 10 at the outputs of the VCO1 and VCO8 that are independent of each other in the first PLL and the second PLL, there is no influence between the first PLL and the second PLL. The integration constants of the integrators 7 and 11 are set appropriately.

  In the Q measurement for measuring the viscosity, for example, the phase shift amount of one phase shifter 5 is set to −45 °, and the phase shift amount of the other phase shifter 9 is set to + 45 °.

  Since the oscillation frequency of the first PLL and the oscillation frequency of the second PLL, which are independent from each other, are frequencies for measuring a half width for measuring a desired physical quantity (for example, viscosity), for example, each frequency is set by a frequency counter. Measure to determine the difference between the two frequencies.

When the oscillation frequency of the first PLL is ω1 and the oscillation frequency of the second PLL is ω2 (ω2> ω1), when the half width is smaller than the oscillation frequency,
Resonance frequency ω0 = (ω1 + ω2) / 2
It can be said.

The Q of this oscillator is
Q = (ω1 + ω2) / 2 / (ω2-ω1)
Thus, Q can be measured.

  By this measuring method, the liquid viscosity prescribed in the above-mentioned JIS8803: 2011 can be continuously measured.

  Note that the phase does not necessarily have to be fixed at -45 ° and -135 °, and the Q value can be obtained by measuring the oscillation frequency at a fixed phase using two PLL oscillators.

  Various electrical methods for capturing the phase change have been proposed, but the present invention can be applied to any method.

  FIG. 2 is a block diagram showing another embodiment of the present invention, and the same reference numerals are given to portions common to FIG. In the embodiment of FIG. 2, the output signal of the VCO 1 constituting the first PLL and the output signal of the VCO 8 constituting the second PLL are inputted to the multiplier 12 and multiplied, and the output of the multiplier 12 is LPF. The difference frequency is obtained in an analog manner by outputting via the (low-pass filter) 13.

  When the output signal of the VCO 1 constituting the first PLL and the output signal of the VCO 8 constituting the second PLL are multiplied by the multiplier 12, the multiplier 12 outputs the sum frequency and the difference frequency of the two input frequencies. . Thus, by extracting only the difference signal using the LPF 13, a continuous output of the difference frequency for measuring Q can be obtained.

  In the above-described embodiment, an example in which the viscosity is measured as a physical quantity has been described. However, the physical quantity is not limited to the viscosity, and the present invention is used to measure the Q value of other sensors and resonant circuits that operate according to the same principle. Applicable as a circuit.

  As described above, according to the present invention, it is possible to realize a physical quantity measuring apparatus that is less robust due to temperature, time, etc., is robust and stable, and can continuously measure a desired physical quantity.

1, 8 Voltage controlled oscillator (VCO)
2, 4 Amplifier 3 Sensor 5, 9 Phase shifter 6, 10 Phase detector 7, 11 Integrator 12 Multiplier 13 LPF (low pass filter)

Claims (4)

In a physical quantity measuring device configured to measure a desired physical quantity based on the resonance frequency of the sensor,
A first phase-locked loop including the sensor;
A second phase-locked loop including the sensor;
An adder for adding the output signal of the voltage controlled oscillator of the first phase locked loop and the output signal of the voltage controlled oscillator of the second phase locked loop;
And the two phase-locked loops are operated in parallel.   2. The physical quantity measuring device according to claim 1, wherein the Q is measured by setting the phase shift amount of the one phase-locked loop to +45 degrees and the phase shift amount of the other phase-locked loop to -45 degrees. In a physical quantity measuring device configured to measure a desired physical quantity based on the resonance frequency of the sensor,
A first phase-locked loop including the sensor;
A second phase-locked loop including the sensor;
An adder for adding the output signal of the voltage controlled oscillator of the first phase locked loop and the output signal of the voltage controlled oscillator of the second phase locked loop;
A multiplier for multiplying the output signals of the two phase-locked loops;
A low-pass filter that extracts a frequency component of the difference from the output signal of the multiplier;
And a physical quantity measuring device for continuously obtaining a difference frequency component for measuring Q.   4. The physical quantity measuring device according to claim 2, wherein the desired physical quantity is a viscosity.

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