JPH10293053A - Vibration-type measuring instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform a stable and accurate measurement without requiring one's help, for example, even if the viscosity of a fluid changes due to a vibration-type measuring instrument for measuring the mass flow rate and the density of the fluid. SOLUTION: The ratio of a vibration amplitude for the vibration force of a measurement pie is measured by performing a prescribed operation by a CPU 1 based on a drive current that is fed to the excitation coil of the measurement pipe and a signal voltage obtained from the detector of the measurement pipe, namely the output of analog to digital converters AD 1 and 2. Also, the response of a vibration system is maintained nearly constantly, a stable vibration continues, and a measurement is stabilized by automatically changing the amplification factor of an excitation efficiency compensation amplifier GA1 so that the ratio change can be compensated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibratory measuring device for causing at least one measuring tube to resonate and vibrate and measuring at least one of a mass flow rate and a density of a fluid flowing in the measuring tube.

[0002]

2. Description of the Related Art In order to continuously vibrate a measuring tube at a constant amplitude, a signal proportional to the vibration amplitude obtained from a detector of the measuring tube is used to control a current flowing through an exciting coil of the measuring tube. I have. That is, the circuit is controlled so that the relationship between the ratio of the vibration amplitude to the excitation force at the resonance frequency (gain and phase of the measuring tube) and the gain and phase of the circuit satisfies the stable oscillation condition. The stable oscillation condition is that the phase of the loop transfer characteristic is rotated by 360 degrees at the vibration frequency and that the gain is 0 db. Therefore, when the ratio and the phase of the vibration amplitude to the excitation force of the measurement pipe in the closed loop system change due to a change in the viscosity of the fluid to be measured, it is necessary to compensate for those changes by a circuit.

The conventional example shown in FIG. 8 can compensate for the change in the ratio of the vibration amplitude to the excitation force of the measuring tube to some extent. This is a range where the signal voltage of each section is not saturated with the power supply voltage, which is about 10 times as large. However, the change in the ratio (gain) of the vibration amplitude to the vibrating force of the measuring tube due to the change in the viscosity of the fluid, as shown in FIG.
In some cases, the amplification factor of the amplifier or the current booster at the subsequent stage of the detector is manually adjusted according to the applied fluid. FIG. 9B shows an example of a phase change of the vibration amplitude.

On the other hand, a beat phenomenon in which the envelope of the vibration amplitude oscillates due to the phase change of the vibration amplitude with respect to the exciting force of the measuring tube may occur as shown in FIG. By adjusting the amplification factor of the error amplifier, it is possible to respond. FIG.
Oscillation start of the mode with low setting amplitude in
The clock of the band-pass filter (BPF) composed of the switched capacitor filter uses the automatic sweep of the phase-locked loop PLL1 at the time of power-on, and the oscillation amplitude gradually increases at the frequency where the PLL output frequency and the mode frequency of the low setting amplitude match. , And the PLL 1 locks at that frequency, and a mechanism of establishing a continuous oscillation is used.

[0005]

As described above, in the prior art, when the ratio of the vibration amplitude to the exciting force of the measuring tube changes greatly, the measuring tube does not vibrate at the set amplitude. It is necessary to change the amplification factor of the amplifier or the current booster at the subsequent stage of the detector, and there is a problem that frequent manual operations are required. Also, when there is a phase change of the vibration amplitude with respect to the exciting force of the measuring tube, a beat phenomenon occurs, which has a negative effect on the flow measurement fluctuations. In this case as well, it is necessary to manually change the amplification factor of the error amplifier. Yes, there is a problem that humans are frequently required.

[0006] Furthermore, as for the activation of the vibration in the mode with a low set amplitude, the power is turned on and off repeatedly to be activated, so that there is a problem that several trials are required and it takes time. In addition, if the amplification factor of the amplifier, current booster or error amplifier after the detector is not appropriate,
There is also a problem that the vibration does not start even if the power is turned on and off many times. In addition, the fact that the frequency change rate of the PLL output when the power is turned on is a rate at which resonance oscillation can be started, and that the oscillation frequency suddenly changes due to temperature and viscosity changes.
There is a problem that the PLL must be designed so as to satisfy the two characteristics that the L output can follow.
Accordingly, it is an object of the present invention to eliminate the need for frequent manual intervention and to stably start vibration in a mode having a low set amplitude in a short time.

[0007]

The ratio between the drive current applied to the excitation coil of the measuring tube and the signal voltage proportional to the vibration amplitude obtained from the detecting section of the measuring tube is measured, and the ratio of the vibration amplitude to the exciting force of the measuring tube is measured. The change in the ratio is measured, and the amplification factor of the excitation efficiency amplifier is changed so as to compensate for the change in the ratio. Thereby, the responsiveness of the vibration system is always kept constant, so that a constant vibration amplitude characteristic can be always realized. In addition, an appropriate amplification factor of the error amplifier is obtained by measuring a beat amount when the amplification factor of the error amplifier is changed or by measuring a loop transfer characteristic of the amplitude stabilization loop. As a result, the amplification factor of the error amplifier corresponding to the change in the phase of the vibration amplitude with respect to the excitation force of the measuring tube can be set, and beat can be prevented. As a result, a stable vibration amplitude can be realized, and therefore, the stability of the measurement of the mass flow rate is also improved.

[0008] Further, when the power supply is turned on, the mode for starting the mode having a low set amplitude is not automatically sweeping the output frequency of the PLL, but a processing device (microcomputer (microcomputer)).
And the like, and outputs a frequency of a mode having a low set amplitude in response to a command from the CPU) to start vibration. Also, at startup, the change in the ratio of the vibration amplitude to the excitation force of the measuring tube is unknown,
The amplification factor of the excitation efficiency amplifier and the amplification factor of the error amplifier are gradually increased so as to compensate for the change in the ratio. For this reason,
The responsiveness of the PLL can be designed without considering the responsiveness of the automatic sweep at the time of startup, and reliable startup based on the judgment of the microcomputer becomes possible.

[0009]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention. Here, one of the two detectors (upper side in FIG. 1) provided in the measuring tube is used to vibrate in a high-frequency mode, and the other (FIG. 1).
In the figure, the detector is vibrated in a low-frequency mode using the lower detector. And the amplitude in the high frequency mode is
It is assumed that the amplitude is about 100 times larger than the amplitude in the low frequency mode.

The circuit in the mode with a large amplitude corresponds to the upper half of FIG. 1, and a signal proportional to the vibration amplitude obtained from the detector of the measuring tube is amplified by the amplifier A1 to detect the amplitude. Provided with a rectifier circuit RE1 and a smoothing circuit ST1. This amplitude corresponds to the value corresponding to the target amplitude and the error amplifier A
M1 is compared, and a deviation (current command value) corresponding to an error from the target amplitude is obtained. By forming a closed loop for oscillating the measuring tube with a signal obtained by multiplying the deviation and the amplifier output signal at the subsequent stage of the detector by a multiplier, it is possible to perform amplitude control that matches the target amplitude.

However, when the viscosity of the fluid to be measured increases, the ratio of the vibration amplitude to the vibrating force of the measuring tube (detector voltage / drive current) decreases, and continuous vibration cannot be performed. On the other hand, when the operation is performed with a circuit gain suitable for a highly viscous fluid, if the viscosity decreases and the ratio of the vibration amplitude to the vibrating force of the measuring tube increases, the current command value decreases and the signal-to-noise ratio S / N worsens,
Stable amplitude control cannot be performed.

For this reason, it is necessary to change the circuit gain in response to a change in the ratio of the vibration amplitude to the excitation force of the measuring tube. In FIG. 1, the vibration amplitude of a mode having a large set amplitude is measured by an analog / digital converter (also simply referred to as a converter or an AD converter) AD1, and the drive current is measured by a converter AD2. Although the detector voltage is a sine wave, since the rectified and smoothed signal is AD-converted,
A low-speed AD converter is sufficient. Although the drive current is also a sine wave, the current command value which is almost a DC signal is represented by A
Since D-conversion is performed, a low-speed AD converter is also sufficient. The change in the ratio of the vibration amplitude to the excitation force of the measuring tube is determined from the values taken in by these two AD converters, and the amplification factor of the excitation efficiency compensation amplifier GA1 is set to compensate for the change. The actual drive current is determined by the excitation efficiency compensation amplifier GA1.
And the converter AD2. Note that the current value applied to the excitation coil of the measuring tube can also be obtained directly by, for example, rectifying, smoothing, and AD converting the output of the current booster IB.

When the amplification factor of the excitation efficiency compensating amplifier is changed based on the change in the ratio of the vibration amplitude to the excitation force obtained as described above, the excitation is performed for each change in the ratio of the vibration amplitude to the minute excitation force. If the amplification factor of the efficiency compensation amplifier is changed, an error is given to the flow measurement until the fluctuation due to the change in the amplification factor is stabilized. Therefore, the ratio of the amplification factor of the excitation efficiency compensation amplifier to be set obtained from the change in the amplification factor of the excitation efficiency compensation amplifier that has been set and the ratio of the vibration amplitude to the excitation force is a certain constant value (for example, ± 10%). Only when the above is satisfied, the amplification factor of the excitation efficiency compensating amplifier is changed to reduce the occurrence of flow rate measurement errors until the vibration is stabilized. That is, a hysteresis characteristic is given to the change in the amplification factor of the excitation efficiency compensation amplifier.

Further, the phase of the vibration amplitude (detector voltage / drive current) with respect to the exciting force of the measuring tube also changes due to a change in the viscosity of the fluid to be measured. This change deteriorates the stability of the vibration control system and causes a beat phenomenon in which the vibration amplitude changes at a low frequency, as described with reference to FIG. This beat phenomenon occurs because the gain characteristic of the amplitude envelope is larger than the phase characteristic of the amplitude envelope (to satisfy the oscillation condition at the beat frequency).
In the circuit of FIG. 1, such a beat phenomenon can be suppressed by lowering the amplification factor of the error amplifier AM. However, if the amplification factor of the error amplifier is too low, the error between the amplitude command value and the actual amplitude value becomes large, causing a problem that the responsiveness of the vibration control due to disturbance is deteriorated.
Therefore, it is necessary to appropriately select the amplification factor of the error amplifier.

In the circuit shown in FIG. 1, the beat amount when the amplification factor of the error amplifier is changed within a certain range is obtained by using the converter AD3 during calibration in which the flow rate measurement is not performed, and an appropriate value is obtained from the data. Set the amplification factor of the error amplifier. As an example of a method of obtaining an appropriate amplification factor of the error amplifier, for example, in the data obtained as shown in FIG. 2, a certain ratio (for example, 15%) of the amplification factor of the error amplifier whose beat amount exceeds a certain threshold value is used. %), That is, a method in which the amplification factor of the error amplifier is set to a value on the left side of the amplification factor of the error amplifier obtained by the threshold value in FIG. As described above, the error in the amplification factor setting of the error amplifier can be reduced because the data with a large beat amount and high accuracy is used. However, such a method can be performed only at the time of calibration, and cannot cope with a sudden change in viscosity during flow rate measurement. For this reason, there is a method in which the beat amount is constantly measured, and when the beat amount increases, the amplification factor of the error amplifier is reduced by a certain ratio (for example, 80%) to reduce the beat amount. Further, when the amplification factor of the error amplifier must be increased, it is detected from a decrease in the vibration amplitude (or oscillation stop), and the amplification factor of the error amplifier is adjusted in the same manner as described above.

It is necessary to adjust the amplification factors of the excitation efficiency compensation amplifier and the error amplifier independently of each other in a mode having a large set amplitude and a mode having a small set amplitude. The mode with a small setting amplitude is smaller than the mode with a large setting amplitude.
Since the amplitude is about 1/100, a band-pass filter (BPF) using a switched capacitor filter is used in FIG. 1 to detect a mode having a small set amplitude. However, the amplification of the excitation efficiency compensation amplifier GA2 and the error amplifier AM2 is performed. Adjustment of the rate can be handled in the same manner as in the mode with a large set amplitude.

FIG. 3 is a flowchart for explaining the vibration starting operation in FIG. In the activation sequence, a mode with a large set amplitude (the left side of the dashed line) is activated first, and a mode with a small set amplitude (the right side of the dashed line) is activated later. In the reverse sequence, a mode with a large set amplitude is started after a mode with a small set amplitude is started, and a moment occurs when the amplitude levels of the two modes are close to each other. At this time, there is a moment when the output amplitude of the detector becomes close to zero due to the phase relationship between the two modes, and at this moment, the comparator output in the mode with a small set amplitude is disturbed, the PLL is unlocked, and the vibration stops. Therefore, they cannot be hired.

When the mode with a large set amplitude is started, oscillation starts when the amplification factors of the excitation efficiency compensation amplifier and the error amplifier satisfy the stable oscillation condition (see YES in step S1). Since the viscosity and the ratio and phase of the vibration amplitude to the vibrating force of the measuring tube are unknown at the time of startup, the oscillation efficiency compensation amplifier and the amplification factor of the error amplifier are gradually increased until the start of oscillation. For the mode with small set amplitude, BP
Since a switched capacitor filter is used as F, the center frequency of the BPF coincides with the resonance frequency when the clock applied thereto becomes a fixed multiple (for example, 100 times) of the resonance frequency, and oscillation starts. As the clock of the BPF, a clock obtained by comparing a sine wave of an oscillation frequency component and multiplying (for example, 100 times) by a PLL is used.

In the conventional method, when the power is turned on, the PLL
The output clock sweeps gradually from a lower frequency to a higher frequency. When the center frequency of the BPF coincides with the resonance frequency at the intermediate frequency, the resonance oscillation of the mode with a small set amplitude is activated. However, if the change speed of the PLL clock frequency when the power is turned on is fast, the center frequency of the BPF passes through the resonance frequency before the PLL locks due to an increase in the detector output of the measuring tube, and a continuous oscillation is established. do not do. Therefore, it is necessary to increase the time constant of the lag-lead filter used in the PLL in order to slow down the change in the PLL clock frequency. However, in this case, there is a problem that it is impossible to cope with a sudden change in the resonance frequency due to a sudden change in the fluid density or the temperature.

Therefore, the clock frequency sweep of the BPF at the time of startup is controlled by a frequency variable clock circuit and a CPU (arithmetic processing unit including a microcomputer) so that the clock frequency sweep has a sufficient time.
When the center frequency of the signal coincides with the resonance frequency of the mode with a small set amplitude, the signal amplitude generated in the detector of the measuring tube increases, the comparator output cycle stabilizes, and the PLL lock stabilizes. The clock to be switched is switched to a PLL signal by a switch. As a result, a reliable and stable start-up is realized, and a lag-lead filter constant that can follow a change in the resonance frequency at a high speed is used to cope with a frequency change.

Further, the clock switching is desirably performed when the phase of the variable clock by the CPU matches the phase of the clock by the PLL, since the PLL response after the switching is not disturbed. This control is performed as shown in FIG. 4. The counter CT counts the phase difference between the variable clock and the PLL signal, compares the value with a preset count value (corresponding to the phase difference), and compares the two clocks. When the phase difference becomes equal to or less than the set value, for example, a signal of “H” is output, and when the switching command from the CPU becomes, for example, “H”, the clock of the BPF is varied via an AND gate and a latch circuit. Switch from clock to PLL signal. Since this signal switching and the BPF clock are TTL level,
It can be configured using gate logic.

In the mode with a small set amplitude, similarly to the mode with a large set amplitude, in order to perform stable continuous oscillation, a closed loop system composed of a measuring tube and a circuit must satisfy a stable oscillation condition. If the measuring tube is not vibrating, the viscosity and the ratio of the vibration amplitude to the vibrating force of the measuring tube are unknown, so the amplification factors of the excitation efficiency compensation amplifier and error amplifier are gradually increased as in the mode with the large set amplitude. While starting to vibrate.

FIG. 5 is a block diagram showing a second embodiment of the present invention. Although FIG. 2 shows only the method of adjusting the amplification factor of the error amplifier in the mode having a large set amplitude,
Application to a mode with a small set amplitude is also possible. Also,
As shown in the first embodiment of FIG. 1, it is possible to use both the amplification factor adjustment of the excitation efficiency compensation amplifier and the start sequence of each mode. The loop transfer characteristic of the amplitude control system is generally as shown in FIG. In order to measure this characteristic in a vibration type measuring instrument, a sine wave which becomes a disturbance is input to one terminal of the adder before the error amplifier, and how much this signal component is detected before the adder is determined. The measurement is performed while changing the frequency of the input disturbance sine wave. In this way, the amplitude ratio and phase difference between the signal component having the same frequency as the disturbance signal detected in the previous stage of the adder and the added disturbance signal become a loop transfer characteristic. As an apparatus for measuring such characteristics, for example, a servo analyzer as shown in FIG. 7 is commercially available.

That is, if the same functions as those of FIG. 7 (sweep disturbance generator, signal acquisition unit, amplitude ratio / phase difference calculation unit) are added, the desired loop transfer characteristic can be obtained, and the amplification factor of the error amplifier can be reduced. Can be set appropriately. However, in general, since the approximate control performance can be obtained from the gain margin and the phase margin of the loop transfer characteristic,
It is not necessary to measure over a wide range of frequencies as shown in FIG. Also, if the control loop structure is determined,
As shown in FIGS. 6A and 6B, since there is a certain relationship between the margin of gain and the margin of phase, it is sufficient to measure only one of them.

FIG. 5 shows an example of measuring the gain margin. In the figure, a disturbance sine wave signal for measuring the loop transfer characteristic is generated by a VCO (voltage controlled oscillator).
The output of this VCO is input to an LPF (low-pass filter) to create a sine wave of only the fundamental frequency, and the disturbance signal amplitude is a level that has good gain surveillance measurement sensitivity and does not affect mass flow rate measurement. Is determined by the CPU and controlled by the gain control amplifier A3. This disturbance sine wave signal is input to one end of an adder at the previous stage of the error amplifier AM1. As is clear from the relations (a) and (b) in FIG. 6, since the gain margin can be measured at a frequency at which the phase of the loop transfer characteristic becomes 0, it is necessary to create a disturbance at that frequency. Therefore,
The VCO is controlled by comparing the phases so that the phase of the loop transfer characteristic becomes zero. The gain margin is obtained by adding the disturbance sine wave signal to be added and the signal at the previous stage of the adder to HP
F (high-pass filter), rectifier circuit, smoothing circuit extract only the same frequency components as the sine wave for disturbance, A / D converted and calculated from the ratio with the signal taken into CPU (processing unit including microcomputer) Calculate in the section. From the gain margin thus obtained, an appropriate amplification factor of the error amplifier is obtained, and the value is automatically set. In this way, since only the minimum necessary gain margin is measured, there is an advantage that the measurement time is shortened as compared with the case of measuring over the entire frequency range as shown in FIG.

[0026]

According to the present invention, the vibration amplitude with respect to the exciting force of the measurement tube is determined from the drive current applied to the excitation coil of the measurement tube and the ratio of the signal voltage proportional to the vibration amplitude obtained from the detection section of the measurement tube. The change of the ratio is measured, and the amplification factor of the excitation efficiency compensation amplifier is changed so as to compensate for the change in the ratio.Thus, the response of the vibration system is always kept constant, and the stable vibration amplitude control characteristic is obtained. The advantage of realization is obtained. In addition, since the beat amount when the amplification factor of the error amplifier is changed or the loop transfer characteristic of the amplitude stabilization loop is measured to determine the appropriate amplification factor of the error amplifier, The amplification factor of the error amplifier can be set corresponding to the change in the phase of the vibration amplitude with respect to the excitation force, and there is an advantage that beat can be prevented. Furthermore, when starting the mode with a low set amplitude, the
Instead of automatic sweeping of the output frequency of the LL, the CPU outputs a frequency in a mode with a low set amplitude in response to a command from the CPU to start vibration, and at startup, the change in the ratio of the vibration amplitude to the excitation force of the measuring tube is unknown. Therefore, the amplification ratio of the excitation efficiency compensation amplifier and the error amplifier is gradually increased to compensate for the change in the ratio, so that the response of the PLL can be designed without considering the response of the automatic sweep at startup. , CP
This provides an advantage that reliable activation based on the judgment of U is possible.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a relationship between an amplification factor of an error amplifier and a beat amount.

FIG. 3 is a flowchart illustrating a procedure for starting vibration.

FIG. 4 is a block diagram illustrating a BPF clock switching timing control circuit;

FIG. 5 is a configuration diagram showing a second embodiment of the present invention.

FIG. 6 is an explanatory diagram of a loop transfer characteristic of an amplitude control system.

FIG. 7 is a block diagram illustrating a general example of a method of measuring loop transfer characteristics of an amplitude control system.

FIG. 8 is a configuration diagram showing a conventional example.

FIG. 9 is an explanatory diagram of transfer characteristics of a measurement tube.

FIG. 10 is an explanatory diagram of a beat phenomenon of a measurement tube.

[Explanation of symbols]

AD: analog-to-digital converter, DA: digital-to-analog converter, A: amplifier, RE: rectifier circuit, ST: smoothing circuit, EA: error amplifier, GA: excitation efficiency compensation amplifier, IB: current booster, CPU: microcomputer, etc. Processing device, BPF: band-pass filter (band-pass filter), HPF: high-pass filter.

Claims (12)

[Claims] 1. A vibratory measuring device for causing at least one measurement tube to vibrate at resonance and measuring at least one of a mass flow rate and a density of a fluid flowing in the measurement tube, wherein a viscosity of the fluid in the measurement tube changes. A vibration characterized by detecting a change in the ratio of the vibration amplitude to the excitation force including the above, controlling the amplification factor of the excitation efficiency compensation amplifier to compensate for the change in the ratio, and enabling stable continuous vibration. Type measuring instrument. 2. A method of measuring a ratio of a vibration amplitude to an exciting force of a measuring tube from a ratio of a signal amplitude proportional to vibration obtained from a detector of the measuring tube and a current value applied to an exciting coil of the measuring tube. The vibration-type measuring device according to claim 1, wherein: 3. A rectifier circuit downstream of the detector of the measuring tube,
A smoothing circuit and an AD converter are provided to measure a signal proportional to the vibration of the measuring tube, while the exciting current command signal and A
3. The method according to claim 2, wherein a current value supplied to the exciting coil of the measuring tube is measured directly through a rectifier circuit, a smoothing circuit, and an AD converter.
The vibration type measuring device according to 1. 4. The vibration type measuring instrument according to claim 1, wherein a hysteresis characteristic is given to a change in an amplification factor of said excitation efficiency compensating amplifier. 5. A vibratory measuring device for causing at least one measuring tube to resonate and measure at least one of a mass flow rate and a density of a fluid flowing in the measuring tube, wherein the viscosity of the fluid in the measuring tube changes. To detect the change in the vibration amplitude phase difference with respect to the excitation force including the above, and compensate for the change in the vibration amplitude control performance due to the phase difference change by controlling the amplification factor of the error amplifier to enable stable continuous vibration. Characteristic vibration type measuring instrument. 6. A method of measuring a variation width (beat amount) of a vibration amplitude generated in a detector of a measuring tube while changing an amplification factor of the error amplifier, and indirectly obtaining a phase change of the vibration amplitude with respect to the excitation force. 6. The vibration type measuring instrument according to claim 5, wherein an appropriate amplification factor of the error amplifier is obtained. 7. A deterioration in vibration amplitude control performance caused by a phase change of the vibration amplitude with respect to the exciting force is detected from an increase in the change width (beat amount) of the vibration amplitude generated in the detector of the measuring tube. 6. The method according to claim 5, wherein the amplification factor of the error amplifier is reduced to suppress the variation width of the vibration amplitude.
The vibration type measuring device according to 1. 8. A method for causing at least one measurement tube to vibrate in resonance, detecting a change in a ratio of a vibration amplitude to an exciting force including a case in which a viscosity of a fluid flowing in the measurement tube changes, and compensating for the change in the ratio. Control the amplification factor of the excitation efficiency compensating amplifier so as to detect the change in the phase difference of the vibration amplitude with respect to the exciting force including the case where the viscosity of the fluid in the measurement tube changes. While controlling the amplification factor of the error amplifier to compensate for the change in control performance, at least one of the mass flow rate and the density of the fluid flowing in the measurement tube is measured, and the first resonance vibration mode and the second resonance vibration mode are measured. The measured value is corrected using the resonance frequency, and the vibration type measuring instrument with the difference between the two vibration modes vibrates in the order of the mode with the larger set amplitude and the mode with the smaller set amplitude. Starting with, at the time of start-up of each mode vibration type measuring instrument is characterized by providing a start control circuit for the gradually increasing the amplification factor of the amplification factor and the excitation efficiency compensation amplifier of the error amplifier. 9. A band-pass filter comprising a switched capacitor filter is provided at a stage subsequent to the detector in the mode having a small set amplitude, and the activation control circuit is formed by at least a frequency variable clock circuit, an arithmetic processing unit, and a phase locked loop. When the power is turned on, the clock frequency sweep of the band-pass filter is performed by controlling the frequency variable clock circuit from the processing device,
When the center frequency of the band-pass filter matches the mode in which the set amplitude is small, the signal amplitude generated in the detector increases, and the lock of the phase-locked loop is stabilized, the clock of the band-pass filter is set to the phase-locked loop. 9. The vibration type measuring instrument according to claim 8, wherein the output is switched to an output from the vibration measuring instrument. 10. The vibration type measurement according to claim 9, wherein the switching of the clock of the band-pass filter is performed when the phase of the variable frequency clock coincides with the phase of the output signal from the phase locked loop. vessel. 11. A disturbance sine wave generator capable of controlling at least the amplitude and frequency, an addition circuit for adding the disturbance sine wave to a stage preceding the error amplifier, and the same disturbance as the disturbance occurring before the addition circuit. A detection circuit for detecting the frequency component of the above, and an operation for measuring the amplitude control performance from the ratio between the disturbance sine wave component and the same frequency component as the disturbance generated in the preceding stage of the addition circuit, and calculating an appropriate amplification factor of the error amplifier. The vibration-type measuring device according to claim 5, further comprising: a processing device. 12. The phase of the disturbance sine wave is controlled by the arithmetic processing unit such that the phase of the disturbance sine wave and the same frequency component as the disturbance generated in the preceding stage of the signal adding circuit are always 0 degrees. Then, an appropriate amplification factor of the error amplifier is obtained by using an amplitude ratio (gain margin) between the disturbance sine wave and the same frequency component as that of the disturbance generated in a stage preceding the adding circuit of the signal. Item 12. The vibration-type measuring device according to item 11.