JPH0643053A - Vibration type sensor - Google Patents

Abstract

PURPOSE:To make it possible to prevent the abnormal output caused by the disturbance of a vibrator by forming an abnormal flag with an abnormality detecting means when a control signal is monitored and the control signal exceeds a reference value, monitoring the flag with an operating part, and outputting a normal signal. CONSTITUTION:When disturbance is mixed into a detected signal V12 in the form of a shock or the like, the amplitude of the detected signal is temporarily decreased. Then, an error amplifier 14 increases a control signal Vc2. When this value exceeds a reference voltage Es3, a comparator 19 outputs a comparison signal Vc3. Then, an abnormality detecting circuit 20 detects the fact that the signal Vc3 becomes an H level and forms an abnormality flag AF at the output terminal for a specified time. An operating part 21 monitors the flag AF. When the flag rises up, the data at the previous time are held and outputted through an output terminal 18. A reset signal RS for resetting the flag AF is outputted into the circuit 20, and the flag AF is reset. Since the operating part 21 outputs the result of the previous operation, the errorneous signal counted with a countre 16 is not used for the operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration type sensor for detecting a physical quantity from a change in frequency of self-excited oscillation which changes corresponding to a physical quantity such as differential pressure and pressure, and is particularly stable against disturbance. The present invention relates to an improved vibration sensor.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing the structure of a conventional vibration sensor. The vibrator 10 has a structure in which a diaphragm is formed of, for example, silicon single crystal, and a beam having a cavity formed by etching in the periphery thereof is formed in an H shape integrally with the diaphragm. A drive signal is input to one end of the beam to vibrate the beam by the interaction between the drive signal and the magnetic field, and a voltage generated corresponding to the vibration of the beam is output from the other end. In this case, the cavity is evacuated so that it is very sensitive and the beam has a high Q factor.

The oscillating voltage output from the other end of the beam is input to an amplifier 11, where it is amplified and output as a detection signal V _i1 at its output end. The detection signal V _i1 is output to the amplitude control circuit 12, and the amplitude control circuit 12 detects the detection signal V _i1.
Drive voltage V _d1 is controlled to have an amplitude corresponding to a control signal V _c1 , which will be described later, that is, AGC control is performed and the voltage is output to one end of the vibrator 10. As described above, the vibrator 1
0, the amplifier 11, and the amplitude control circuit 12 constitute a self-excited oscillation circuit which is AGC controlled.

Further, the detection signal V _i1 is output to the squaring circuit 13 and rectified therein, and the voltage appearing at the output end thereof is input to one end of the input end of the error amplifier 14. Error amplifier 1
The reference voltage E _S1 corresponding to the reference amplitude As adopted as the proper amplitude of the vibrator 10 is applied to the other end of the input of 4, and the error amplifier 14 determines that the amplitude of the vibration of the vibrator 10 is always this reference. The amplitude control circuit 1 controls the amplitude As, that is, the control signal V _c1 for controlling the reference voltage E _S1 from its output end.
It outputs to 2.

Further, the detection signal V _i1 is applied to the other end of the comparator 15 having the reference voltage E _S2 applied to one end of the input, and the detection signal V _i1 has an amplitude exceeding the reference voltage E _S2 at its output end. The signal V _{i1 is} waveform-shaped and output as the frequency signal F1.

The frequency signal F1 is counted by the counter 16, and the integrated signal N1 is output to the arithmetic unit 17 whose base is a microprocessor. Here, an appropriate calculation is executed to calculate a physical quantity corresponding to the frequency of the vibrator 10 and output it to the output end 18.

[0007]

However, the conventional vibration type sensor as described above has the following problems. This will be described with reference to FIG. FIG. 4A shows an amplifier 1
1 shows the detection signal V _i1 appearing at the output of FIG. ₁ , FIG. 4B shows the drive voltage V _d1 , and FIG. 4C shows the waveform of the frequency signal F1 appearing as the output of the comparator 15.

Now, when a disturbance such as an impact is mixed in the detection signal V _i1 as indicated by Nz in FIG. 4A, the control signal V _c1
Operates to increase the drive voltage V _d1 (see FIG. 4).
In (b), since the Q factor of the vibrator 10 is large, the amplitude of the vibrator 10 does not immediately respond to this, and as shown in FIG. 4A, the detection signal V _i1 is the reference amplitude As during the predetermined time T.
The condition that does not reach is continued. Therefore, at the output end of the comparator 15, as shown by the dotted line in FIG.
A missing tooth occurs at the counter 16 and causes a count error in the counter 16 to cause an error.

[0009]

In order to solve the above problems, the present invention detects a vibrator whose oscillation frequency changes based on a change in a physical quantity, and detects the output of this vibrator and outputs it as a detection signal. And a drive control means for outputting a drive signal to the vibrator as an amplitude to which the detection signal is input and determined by the control signal, and a control signal for comparing the amplitude of the detection signal with the reference amplitude of the vibrator. As an amplitude detection means, an arithmetic means for calculating and outputting an output signal corresponding to the physical quantity above from the frequency of the detection signal, and an abnormality detection for outputting an abnormality flag when the previous control signal deviates from the reference amplitude. Means and monitoring means for monitoring the abnormality flag and retaining the previous data and outputting it as an output signal when the abnormality flag appears.

[0010]

[Operation] The oscillator changes its oscillation frequency based on the change of the physical quantity, and the signal detection means detects the oscillation frequency of this oscillator and outputs it as a detection signal. On the other hand, the drive control means outputs a drive signal to the vibrator as an amplitude determined by the control signal using this detection signal. Further, the amplitude detecting means compares the amplitude of the previous detection signal with the reference amplitude of the vibrator and outputs it as a control signal to the drive control means.
Then, the calculating means calculates and outputs the output signal corresponding to the previous physical quantity from the frequency of the detection signal. Further, the abnormality detecting means outputs an abnormality flag when the previous control signal deviates from the reference amplitude, and the monitoring means monitors this abnormality flag and holds the previous data when this abnormality flag appears. And output as the previous output signal.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of one embodiment of the present invention. The parts having the same functions as those of the conventional vibration sensor shown in FIG. 3 are designated by the same reference numerals, and the description thereof will be appropriately omitted.

Vibrator 10, amplifier 11, amplitude control circuit 1
2, square circuit 13, error amplifier 14, comparator 1
5, the counter 16 and the like have the same configuration as that shown in FIG. The amplitude control circuit 12 outputs the detection signal V _i2 to the predetermined reference amplitude A according to the control signal V _c2 output from the error amplifier 14.
drive voltage V _d2 from its output end so that
It outputs to 0.

On the other hand, the control voltage V _c2 appearing at the output end of the error amplifier 14 is applied to one end of the input of the comparator 19, and the reference voltage E _s3 is applied to the other end. As a result, it is judged whether the control voltage V _d2 exceeds the reference voltage E _s3, and when it exceeds, the level of the comparison signal V _c3 appearing at the output is inverted.

The abnormality detection circuit 20 is provided with this comparator 1
The inversion of the output level of 9 is detected and the abnormality flag AF is set for a predetermined time. The calculation unit 21 uses this abnormality flag AF.
When the error flag is detected, the output of the counter 16 before the abnormality flag AF is set is output to the output end, and the reset signal RS for resetting the abnormality flag AF is output to the abnormality detection circuit 20.

Next, the operation of the vibration type sensor configured as described above will be described with reference to the waveform chart shown in FIG.
Now, as shown in FIG. 2A, when the disturbance Nz is mixed in the detection signal V _i2 in the form of a shock or the like, the detection signal V _i2 is temporarily detected.
The amplitude of _i2 decreases. Therefore, the error amplifier 14 increases its control signal V _c2 as shown in FIG. 2B, but when this value exceeds the reference voltage E _s3 , the comparator 19 causes the control signal V _c2 as shown in FIG. 2C. The comparison signal V _c3 is output.

Therefore, the abnormality detection circuit 20 detects that the comparison signal V _c3 has become high level, and for a predetermined time, as shown in FIG. 2D, the abnormality flag A is output to its output end.
Set up F. The arithmetic unit 21 monitors this abnormality flag AF as shown in FIG. 2E. When the abnormality flag AF is not set, normal signal processing is executed, and when the abnormality flag AF is set, The previous data is held and sent to the output terminal 18, and the reset signal SR for resetting the abnormality flag AF is output to the abnormality detection circuit 20 to output the abnormality flag as shown in FIG. Reset AF.

As described above, when the amplitude of the vibrator 10 suddenly changes and the counter 16 is about to _miscount , the control signal V _c2 changes greatly and the abnormality flag AF is set in the abnormality detection circuit 20. Is monitored and the previous calculation result is output as it is, so the signal miscounted by the counter 16 is not used for the calculation.

In the above description, the comparator 19 is realized by using only one comparator. However, if two comparators are used, it is possible to determine whether the amplitude becomes small or large. However, the abnormality flag can be set.

[0019]

As described above in detail with reference to the embodiments, according to the present invention, the control signal for controlling the amplitude control means is monitored and an abnormality occurs when this control signal exceeds the reference value due to disturbance. Since the abnormality flag is raised by the detecting means and is monitored by the arithmetic unit to output the output signal by replacing it with a normal signal, a sensor for disturbance detection, for example, a simple configuration without using an acceleration sensor, It is possible to prevent abnormal output caused by disturbance of the vibrator, and to realize a stable and highly reliable vibration sensor.

[Brief description of drawings]

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

FIG. 2 is a waveform diagram for explaining the operation of the embodiment shown in FIG.

FIG. 3 is a block diagram showing a configuration of a conventional vibration sensor.

FIG. 4 is a waveform diagram illustrating the operation of the vibration sensor shown in FIG.

[Explanation of symbols]

 10 oscillator 11 amplifier 12 amplitude control circuit 13 square circuit 14 error amplifier 15, 19 comparator 16 counter 17, 21 arithmetic unit 20 abnormality detection circuit

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Koshitaro Koyama 2-932 Nakamachi, Musashino City, Tokyo Yokogawa Electric Co., Ltd. (72) Inventor Kyoichi Ikeda 2-932 Nakamachi, Musashino City, Tokyo Yokogawa Electric Co., Ltd.

Claims (1)

[Claims] 1. A vibrator whose oscillation frequency changes based on a change in a physical quantity, signal detection means for detecting the output of the vibrator and outputting it as a detection signal, and the detection signal which is input and determined by a control signal. Drive control means for outputting a drive signal to the oscillator as an amplitude, an amplitude detection means for comparing the amplitude of the detection signal with a reference amplitude of the oscillator and outputting the control signal, and a frequency of the detection signal. From the calculation means for calculating and outputting an output signal corresponding to the physical quantity, an abnormality detection means for outputting an abnormality flag when the control signal deviates from the reference amplitude, and the abnormality flag is monitored to detect this abnormality flag. A vibrating sensor comprising: a monitoring means for holding the data before this when it appears and outputting it as the output signal.