JP2605497B2 - Vibration sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration sensor for detecting a physical quantity from a change in the frequency of self-excited oscillation that changes in response to a physical quantity such as a differential pressure and a pressure. 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 configuration in which a diaphragm is formed of, for example, silicon single crystal or the like, and a beam in which a cavity is formed by etching is integrally formed with the diaphragm in an H shape. A drive signal is input to one end of the beam, the beam is vibrated by the interaction of the drive signal with a magnetic field, and a voltage generated in response to the vibration of the beam is output from the other end. In this case, since the portion of the cavity is evacuated, the beam has a very high sensitivity and a high Q factor.

[0003] An 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 _Vi1 at its output end. This detection signal _Vi1 is output to the amplitude control circuit 12, and the amplitude control circuit 12 outputs the detection signal _Vi1.
Controls the driving voltage V _d1 so as to have an amplitude corresponding to a control signal V _c1 described later, that is, performs AGC control and outputs the driving voltage to one end of the vibrator 10. As described above, the vibrator 1
0, an amplifier 11, and an amplitude control circuit 12 constitute a self-excited oscillation circuit controlled by AGC.

The detection signal V _i1 is output to a squaring circuit 13 where it is rectified, and the voltage appearing at its output terminal is input to one end of an input terminal of an error amplifier 14. Error amplifier 1
A reference voltage E _S1 corresponding to a reference amplitude As adopted as an appropriate amplitude of the vibrator 10 is applied to the other end of the input of the input 4. A control signal V _c1 for controlling the amplitude As, that is, the reference voltage E _S1 , is output from its output terminal to the amplitude control circuit 1
2 is output.

Further, the detection signal V _i1 is applied to the other end of the comparator 15 to which the reference voltage E _S2 is applied at one end of the input, and the detection signal having an amplitude exceeding the reference voltage E _S2 at the output end. The waveform of the signal _{Vi1 is} shaped and output as a frequency signal F1.

The frequency signal F1 is counted by a counter 16 and the integrated signal N1 is output to a calculation unit 17 based on a microprocessor. Here, an appropriate calculation is performed to calculate a physical quantity corresponding to the frequency of the vibrator 10 and output it to the output terminal 18.

[0007]

However, the above-mentioned conventional vibration type sensors have the following problems. This will be described with reference to FIG. FIG. 4A shows an amplifier 1.
Detection signal V _i1 appearing at the output of the 1, 4 (b) is the drive voltage V _d1, FIG. 4 (c) comparator - shows the waveform of the frequency signal F1 which appears as an output of the motor 15, respectively.

Now, as shown by Nz in FIG. 4A, when a disturbance such as an impact is mixed into the detection signal _Vi1 , the control signal _{Vc1 is generated.
Operates} to increase the drive voltage V _d1 (see FIG. 4).
(B)) is, since Q Fuakuta of the vibrator 10 is large does not respond immediately to the amplitude of the vibrator 10 which, during the reference amplitude As of the detection signal V _i1 is the predetermined time T as shown FIGS. 4 (a)
The state which does not reach continues. Therefore, the frequency signal F1 is output to the output terminal of the comparator 15 as shown by a dotted line in FIG.
, And the counter 16 causes a count error, thereby causing an error.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-described problems, the present invention provides a vibrator whose oscillation frequency changes based on a change in a physical quantity, and detects an output of the vibrator and outputs it as a detection signal. Signal detection means for performing the above operation, amplitude control means for outputting a drive signal to the vibrator as an amplitude determined by the control signal when the detection signal is input, and comparing the amplitude of the detection signal with a reference amplitude of the vibrator. Amplitude detecting means for outputting the control signal as a control signal, calculating means for calculating and outputting an output signal corresponding to the physical quantity from the frequency of the detection signal, and an abnormality flag when the control signal is out of a normal amplitude range. And a monitoring means for monitoring the abnormality flag and, when the abnormality flag appears, retaining the previous data and outputting the data as the output signal.

[0010]

[Operation] A vibrator changes its own oscillation frequency based on a change in a physical quantity. The signal detecting means detects the oscillation frequency of the vibrator and outputs it as a detection signal. On the other hand, vibration
The width control means uses the detection signal to output a drive signal to the vibrator as an amplitude determined by the control signal. The amplitude detecting means compares the amplitude of the detection signal with the reference amplitude of the vibrator and outputs the control signal to the amplitude control means.
Then, the calculating means calculates and outputs an output signal corresponding to the preceding physical quantity from the frequency of the detection signal. Further, the abnormality detection means outputs an abnormality flag when the previous control signal is out of the range of the normal amplitude, and the monitoring means monitors the abnormality flag, and when the abnormality flag appears, retains the data before this. And outputs it as the previous output signal.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS 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. Parts having the same functions as those of the conventional vibration type sensor shown in FIG. 3 are denoted by the same reference numerals, and the description thereof will be appropriately omitted.

Oscillator 10, amplifier 11, amplitude control circuit 1
2, squaring circuit 13, error amplifier 14, comparator 1
5, the counter 16 and the like have the same configuration as the configuration shown in FIG. The amplitude control circuit 12 controls the detection signal V _{i2 according} to the control signal V _c2 output from the error amplifier 14 to a predetermined reference amplitude A.
drive voltage V _d2 from the output end of the vibrator 1
0 is output.

Meanwhile, the control voltage V _c2 at the output terminal of the error amplifier 14 comparator - is applied to one end of the input data 19, and the other end reference voltage E _s3 is applied. Thus, it is determined whether or not the control voltage _Vd2 has _{exceeded the} reference voltage _Es3 . When the control voltage _Vd2 has _{exceeded the} reference voltage _Es3 , the level of the comparison signal _Vc3 appearing at the output is inverted.

The abnormality detecting circuit 20 includes the comparator 1
9 to detect an inversion of the output level, and set an abnormality flag AF for a predetermined time. The calculation unit 21 calculates the abnormal flag AF.
Is detected, the output of the counter 16 before the abnormality flag AF is raised is output to the output terminal, and a 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 having the above-described configuration will be described with reference to a waveform diagram shown in FIG.
Now, when the disturbance Nz is mixed in the form of such an impact in the detection signal V _i2 as shown in FIG. 2 (a), temporarily detection signal V
The amplitude of _i2 decreases. Therefore, although the error amplifier 14 increases the control signal V _c2 as shown in FIG. 2 (b), when this value exceeds the reference voltage E _s3, comparator - motor 19 as shown in FIG. 2 (c) The comparison signal _Vc3 is output.

Therefore, the abnormality detecting circuit 20 detects that the comparison signal _Vc3 has become high level, and for a predetermined period of time, as shown in FIG.
Make F. The arithmetic unit 21 monitors this abnormal flag AF as shown in FIG. 2 (e), executes normal signal processing when the abnormal flag AF is not set, and executes normal signal processing when the abnormal flag AF is set. The previous data is held and transmitted to the output terminal 18, and a reset signal SR for resetting the abnormality flag AF is output to the abnormality detection circuit 20, and as shown in FIG. The AF is reset.

As described above, when the amplitude of the vibrator 10 changes abruptly and the counter 16 is about to _miscount , the control signal _Vc2 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 that the signal miscounted by the counter 16 is not used for the calculation.

In the above description, the configuration is such that only one comparator 19 is used. However, if two comparators are used, either the case where the amplitude becomes small or the case where the amplitude becomes large is used. However, an abnormal flag can be set.

[0019]

As described above, according to the present invention, the control signal for controlling the amplitude control means is monitored, and when the control signal exceeds a reference value due to a disturbance, the abnormality is detected. Since an abnormality flag is set by the detection means and monitored by the arithmetic unit and the output signal is replaced with a normal signal and output, a sensor for disturbance detection, for example, with a simple configuration without using an acceleration sensor, An abnormal output caused by disturbance of the vibrator can be prevented, and a stable and highly reliable vibration sensor can be realized.

[Brief description of the drawings]

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

FIG. 2 is a waveform chart 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]

 DESCRIPTION OF SYMBOLS 10 Oscillator 11 Amplifier 12 Amplitude control circuit 13 Square circuit 14 Error amplifier 15, 19 Comparator 16 Counter 17, 21 Operation part 20 Abnormality detection circuit

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kotaro Koyama 2-9-132 Nakamachi, Musashino-shi, Tokyo Inside Yokogawa Electric Corporation (72) Inventor Kyoichi Ikeda 2-9-132 Nakamachi, Musashino-shi, Tokyo Inside Yokogawa Electric Corporation (56) References JP-A-2-72947 (JP, U) JP-A-1-67544 (JP, U) JP-A-1-172106 (JP, U)

Claims (1)

(57) [Claims] An oscillator whose oscillation frequency changes based on a change in a physical quantity, signal detecting means for detecting an output of the oscillator and outputting it as a detection signal, and the detection signal is inputted and determined by a control signal. Amplitude control means for outputting a drive signal to the vibrator as an amplitude, amplitude detection means for comparing the amplitude of the detection signal with a reference amplitude of the vibrator and outputting the control signal, and a frequency of the detection signal. A calculating means for calculating and outputting an output signal corresponding to the physical quantity, an abnormality detecting means for outputting an abnormality flag when the control signal is out of a normal amplitude range , and an abnormality flag for monitoring the abnormality flag. And a monitoring means for retaining the previous data and outputting it as the output signal when appears.