JPH05651B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention detects the displacement of a movable part in an acceleration detection unit from an equilibrium point, and amplifies the detected value of the displacement, such as in a seismometer. The present invention relates to a digital servo-type vibrometer that drives a movable part of an acceleration detection section so as to return it to an equilibrium position, and is capable of performing measurements using digital values.

[Conventional technology]

As a conventional servo-type vibrometer, for example, as shown in FIG. 7, a servo-type vibrometer 1 includes a detection coil 4 that detects the displacement of a movable part 3 in an acceleration detection part 2 from an equilibrium point. It consists of a converter 5 that amplifies the detected value, a drive coil 7 that moves linearly within the magnet 6 of the acceleration detector 2, an ammeter 8, and the like. When high frequency current is applied from the converter 5 to the detection coil 4,
Eddy currents are generated on the surface of the movable part 3, which is conductive. The strength of this eddy current is determined by the detection coil 4 and the movable part 3.
As a result, the detection coil 4
The inductance of changes as a function of distance.

When the movable part 3 is displaced from the equilibrium point, the detection coil 4
Since a voltage is generated, the output thereof is amplified by the converter 5, extracted as a voltage proportional to the displacement of the movable part 3 through electrical processing, and supplied to the drive coil 7 fixed to the movable part 3. . And moving part 3
A current is supplied so that the movable part 3, the detection coil 4, the transducer 5,
The drive coil 7 forms a servo loop.
Then, since the output current of the converter 5 is proportional to the acceleration that attempts to return the movable part 3 to the equilibrium position, by measuring the output current of the converter 5 with the ammeter 8, the acceleration can be detected. Detecting the acceleration of section 2 as a current value to form a force balance type transducer,
The aim was to obtain a highly accurate vibration meter.

[Problem that the invention seeks to solve]

By the way, since conventional servo-type vibration meters like this one are of the feedback type, they have fewer errors than general vibration meters, but since they use a DC amplifier as a converter, there is a possibility of drift. This may cause an error in the measured value, or the measurement may not be performed properly due to disturbance signals, lightning strikes, etc. In addition, to record measured values, it is necessary to record analog values using a pen recorder or the like, or to convert the measured values to A/D and record them as digital values.
Analog recording has problems in that it is difficult to process and requires a lot of effort to convert to digital values.

The present invention has been made in view of these conventional problems, and an object of the present invention is to provide a digital servo vibrometer that causes fewer errors and facilitates processing of measured values.

[Means for solving problems]

Means for solving the above problems in the present invention includes: a displacement meter that detects the displacement of the movable part of the acceleration detection section of the vibration meter from the equilibrium point; an amplifier that amplifies the measured value of the displacement meter; and a drive section that generates a restoring force that constantly tries to return the movable section to the equilibrium point by the output of an amplifier, and by measuring the current value that drives the movable section, not from the displacement of the displacement meter. In a servo-type vibration meter that measures vibration, instead of an amplifier that amplifies the output value of the displacement meter, a pulse width modulator that converts the output of the displacement meter, and a pulse width modulator that converts the output of the pulse width modulator into a current. a power filter, a driving part for driving the movable part of the acceleration detection part by the output of the power filter to form a servo vibration meter, and a counter for converting the pulse width of the pulse width modulator into a digital value. It is to be configured so as to provide the following.

[Effect]

To explain the operation of the present invention, the displacement of the movable part of the acceleration detection section from the equilibrium point is detected by a displacement meter, the output of the displacement meter is amplified by a pulse width modulator, and the output of the displacement meter is amplified by a pulse width modulator. The output of the device is converted into a current by a power filter, which generates a driving force that serves as a restoring force to return the movable part to the equilibrium point. The current value serving as the driving force in this case is proportional to the acceleration, and therefore the output of the pulse width modulator represents the vibration acceleration. On the other hand, the pulse width that is the output of the pulse width modulator is converted into a digital value by a counter, and the measured value of vibration is expressed as a digital value.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a configuration diagram showing an embodiment of the present invention. The digital servo vibration meter consists of a housing 10 and an acceleration detection section 11, and the acceleration detection section 11 includes a permanent magnet 12 and a permanent magnet 12. There is a movable part 13 that moves relative to each other, and a displacement meter 14 that detects the displacement of the movable part 13 from its equilibrium position. The movable part 13 is made up of an aluminum plate 15 and a drive coil 31, which will be described later. There is also a pulse width modulator 20 that amplifies the measured value of the displacement meter 14.
A part of the pulse width modulator 20 and the pulse width modulator 20 are housed in the housing 10. Note that in this embodiment, the aluminum plate 15 was used to form the movable part 13;
Other metal plates or the like may be used as long as they are non-magnetic conductors.

The displacement meter 14 detects the displacement of the aluminum plate 15 forming the movable part 13 of the acceleration detection section 11 as shown in FIG. The pulse width modulator 20 includes an oscillator 21, an amplifier 22, a comparator 23, an OR circuit 24, etc. as shown in FIG. It consists of

Inside the housing 10, there is a counter unit 25 that converts the pulse width output from the pulse width modulator 20 into a digital value, and the counter unit 25 includes a 40MHz oscillator 26, as shown in FIG. There is an up-down counter 27 in which three four-digit binary units are connected. A power filter 30 for demodulating the output of the pulse width modulator 20 is provided in the acceleration detection section 11 as shown in FIG. Permanent magnet 1 as a movable part drive device
It is adapted to be driven by a drive coil 31 placed in the 2.

When the movable part 13 of the acceleration detection part 11 receives vibration and moves relative to the permanent magnet 12, a process of detecting the displacement of the relative movement will be described.
1MHz in the excitation carrier generator 18 of the displacement meter 14
When this carrier is applied to the coil 17 of the displacement meter 14, the movable part 13 which is conductive
An eddy current is generated on the surface of the aluminum plate 15. The intensity of this eddy current varies depending on the distance between coil 17 and aluminum plate 15, and as a result, the inductance of coil 17 of probe 16 varies as a function of distance. Therefore, the eddy current increases or decreases due to the change in the gap between the coil 17 of the probe 16 and the aluminum plate 15, and the 1MHz AC signal of the excitation carrier increases or decreases, and the next detection smoothing section 19 converts the eddy current into a DC signal. In this way, the displacement of the aluminum plate 15 of the movable part 13 is converted into a DC voltage (see FIG. 3).

This DC voltage signal is sent to the next pulse width modulator 20.
Enter. The pulse width modulator 20 widens the pulse width for large input voltages and narrows the pulse width for small input voltages according to the input DC voltage, and adjusts the pulse width at a pulse frequency of 1kHz. Outputs a modulated pulse. This output is input to the power filter 30 in the acceleration detection section 11 shown in FIG. Return it to the position. Therefore, the movable part 13 is controlled to always return to its original position, which is the equilibrium position, but when such control is performed, the current value of the drive coil 31 is proportional to the acceleration of vibration, so the drive coil Vibration can be measured by measuring the current value of 31, that is, the pulse width of the pulse width modulator 20.

The process of pulse width modulation from a DC voltage is shown in the timing chart of Figure 4, and 1kHz equally spaced rectangular waves as shown in Figure 4a are constantly oscillated from the oscillator 21 shown in Figure 3. . Then, by integrating this rectangular wave, as shown in Figure 4b, a triangular wave is formed that rises linearly when the rectangular wave a is high and falls linearly when the rectangular wave a is low. to occur. The value of the DC voltage that is input to the pulse width modulator 20 is shown as a curve Γ superimposed on the triangular wave b, and the curve Γ represents the center value of the triangular wave b as a zero point. The intersection point of the curve Г and the triangular wave is determined by the comparator 23 in FIG. output in the form

Next, a process of converting the pulse width as the output of the pulse width modulator 20 into a digital value will be explained. Here, apart from the output as power of the pulse width modulator 20, it will be described using the chart shown in FIG.
The value of the DC voltage input to 0 is shown as a curve Г superimposed on a 1 kHz triangular wave, and the curve Г represents the center value of the triangular wave as a zero point. On the other hand, a high frequency of 40 MHz is constantly oscillating from the oscillator 26 of the counter section 25, and the up-down counter 27 is started, and from the point when the rectangular wave a rises from the lower end of the triangular wave b, the 40 MHz high frequency wave of the oscillator 26 is Count oscillation waves. From the start of counting until the point where the curve Г and the triangular wave intersect, the count is added. When the curve Г and the triangular wave intersect, the count is stopped and this count value is set to v ₁ (see Figure 4 e). ). Next, start the attenuating count from the top of the triangular wave b, that is, from the point where the rectangular wave a falls, and continue counting until the point where the curve Г intersects the triangular wave, and set this count value to v ₂ . (See Figure 4f). Since count value v ₁ is an addition value and count value v ₂ is a subtraction value,
The count value remaining in the up-down counter 27 is
v ₁ - v ₂ , and by finding v ₀ = (v ₁ - v ₂ )/2, the input voltage of the pulse width modulator 20 at an intermediate point in time after counting addition and subtraction is a digital value. It will be expressed as v ₀ . Details of the counter section 25 are shown in FIG.
A high frequency of 40 MHz from the oscillator 26 is input to AND gates 28 and 29, and the AND gate 28 performs an addition count, and the AND gate 29 performs a subtraction count. And updown counter 2
The output of 7 passes through a latch circuit 33 and is displayed externally.

In this way, in this embodiment, the amplification after detecting the displacement of the vibration is performed by using a pulse width modulator instead of a DC amplifier, so the output can be easily converted into a digital value, and it can be easily used against disturbance signals and lightning strikes. Become strong. Furthermore, since the up-down counter directly represents the value as a digital value, a vibration meter with a simple structure and high accuracy can be obtained.

Note that in the above embodiment, the movable part 13 is used as a displacement meter.
Although the method using the eddy current generated by the displacement of is described, other methods may be used as long as the displacement can be converted into a DC voltage. FIG. 6 shows an optical displacement meter. When the movable part 35 moves up and down, a pair of light emitting diodes 36 and a light receiving diode 37 provided above and below the movable part 35 detect the displacement of the movable part 35, and an amplifier 38 detects the displacement of the movable part 35. The voltage is then converted into a DC voltage and input to the pulse width modulator, thus replacing the displacement meter 14.

〔Effect of the invention〕

As explained above, according to the present invention, since the amplification after displacement is detected is performed using a pulse width modulator instead of a DC amplifier, there is no drift, and the amplification is performed with the acceleration detection section. Even if the length of the cable between the device and the circuit is increased, it will be more resistant to disturbance signals, lightning strikes, etc., and stable operation can be achieved. In addition, the output of the pulse width modulator can be sent to an AM tape recorder without any conversion.
It can be recorded with a high S/N ratio similar to modulation, and can be demodulated and reproduced. In the present invention, the pulse width can be easily converted into a digital value using an up-down counter, etc., so there is no need for a complicated device such as an A/D converter. This has the advantage that other processing such as data processing becomes easier.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of an embodiment of the present invention, Fig. 2 is a detailed circuit diagram of the acceleration detection section, Fig. 3 is a detailed circuit diagram of the housing section, Fig. 4 is an operation timing chart, and Fig. 5 is a detailed circuit diagram of the acceleration detection section. FIG. 6 is a detailed circuit diagram of the counter section, FIG. 6 is a circuit diagram showing another embodiment of the displacement meter, and FIG. 7 is a configuration diagram of a conventional servo vibration meter. DESCRIPTION OF SYMBOLS 11... Acceleration detection part, 13... Movable part, 14... Displacement meter, 20... Pulse width modulator, 25... Counter part, 30... Power filter, 31... Drive coil (movable part drive device).

Claims (1)

[Claims] 1. A displacement meter that detects the displacement of the movable part of the acceleration detection part of the vibration meter from the equilibrium point, an amplifier that amplifies the measured value of the displacement meter, and the output of the amplifier always returns the movable part to the equilibrium point. In a servo-type vibration meter that measures vibration not from the displacement of the displacement meter but by measuring the current value that drives the movable portion, the displacement meter Instead of an amplifier that amplifies the output value of the displacement meter, a pulse width modulator that converts the output of the displacement meter and a power filter that converts the output of the pulse width modulator into a current are provided, and the acceleration detection is performed using the output of the power filter. 1. A digital servo-type vibrometer, characterized in that a servo-type vibrometer is formed by adding a drive section for driving a movable section of the section, and a counter is provided for converting the pulse width of the pulse width modulator into a digital value.