JPH0711536B2 - Servo type vibrometer - Google Patents

Description

The present invention relates to a servo type vibrometer, and more particularly to a servo type vibrometer having a servo mechanism having a servo induction coil means.

[Outline of Invention]

INDUSTRIAL APPLICABILITY The present invention makes it possible to reliably measure a minute vibration even in a noisy environment due to electromagnetic induction by converting a measurement result into a balanced output signal in a servo vibrometer and outputting the balanced output signal. .

[Conventional technology]

2. Description of the Related Art Conventionally, as a servo type vibrometer of this type, there is one using a servo type vibration pick-up 1 having a built-in servo mechanism as shown in FIG. 2, for example.

That is, the position of the vibration-sensing member 4 made of a weight held in the case 2 via the spring 3 is in the direction indicated by the arrow a relative to the case 2 when the case 2 vibrates. The displacement is detected by the position detector 6 provided on the holding member 5.

Therefore, when the vibration is applied to the case 2, the vibration sensitive member 4 constitutes a displacement portion in which the relative position of the vibration sensitive member 4 with respect to the position detector 6 is displaced according to the acceleration representing the vibration amount.

The position detection unit 6 is composed of a capacitance type position detection device, and a distance d from the electrode 7 attached to the side surface of the vibration sensing member 4 so as to face the position detection unit 6 to the position detection unit 6 is When the vibration-sensitive member 4 changes along with the displacement, the capacitance between the electrode 7 and the position detection unit 6 changes, so that the displacement of the vibration-sensitive member 4 can be detected.

Further, the vibration-sensing member 4 is provided with a bobbin 8 on the side surface on the opposite side of the electrode 7 so that the direction of the displacement direction a of the vibration-sensing member 4 and the tube axis direction match, and the servo induction coil 9 is wound around the bobbin 8. While being turned, the magnetic circuit of the servo induction coil 9
10 is provided in the case 2.

Furthermore, the servo-type vibration pickup 1 is a servo amplifier circuit.
The case 2 vibrates as a whole by having the position detection section 6 have a driving current flowing through the servo induction coil 9 and the output resistance element 12 connected between the servo induction coil 9 and the ground according to the output voltage. At this time, a restraining force is applied to the vibration-sensing member 4 so that the displacement of the vibration-sensing member 4 with respect to the position detection unit 6 is controlled within a minute range.

In this way, when the case 2 vibrates and acceleration is applied to the vibration-sensing member 4 (that is, when the vibration-sensing member 4 is displaced with respect to the position detecting portion 6), the drive current output from the servo amplifier circuit 11 as a servo signal is changed. , The voltage across the output resistance element 12 obtained by passing the drive current to the output resistance element 12 is detected from the output terminals T1 and T2 by utilizing the change to suppress the displacement according to the acceleration. It is transmitted to the outside as a signal.

Thus, the case 2 is attached to the object to be measured, and the terminal voltage of the output resistance element 12 is transmitted from the output terminals T1 and T2 to the measuring instrument main body through the transmission cable to measure the vibration of the object to be measured at a remote location. can do.

[Problems to be Solved by the Invention] However, in such a servo-type vibrometer, an unbalanced-type amplification circuit is used as the servo amplification circuit 11, and a vibration detection signal is transmitted using the amplified output. Therefore, when external noise due to electromagnetic induction is mixed in the output line of the servo amplifier circuit 11, there is a problem that it cannot be removed.

In actuality, when measuring low-level vibration, an extremely small output of about 1 [μV] is obtained as the potential obtained between the output terminals. Therefore, in this case,
In a noisy environment due to the influence of electromagnetic induction, the longer the signal transmission cable between the servo-type vibrometer and the main body of the measuring instrument, the more difficult it is to accurately measure the vibration level in practical use.

The present invention has been made in consideration of the above points, and is intended to propose a servo-type vibrometer capable of accurately measuring a low-level vibration detection signal even in a noisy environment.

[Means for solving problems]

In order to solve such a problem, in the present invention, the spring 3
And a displacement section that has the vibration sensing member 4 and vibrates the vibration sensing member 4 according to the vibration of the object to be measured, and displacement detection sections 6 and 7 that detect the displacement of the vibration sensing member 4 and generate a displacement detection signal. And a first servo amplifier circuit 21A that amplifies the displacement detection signal based on the displacement detection signal in its original phase and outputs a normal phase servo signal, and a phase obtained by inverting the displacement detection signal based on the displacement detection signal. The second servo amplifier circuit 21B which amplifies the signal with the servo amplifier and outputs it as a reverse phase servo signal, and the servo induction coil means 8 and 9 connected in series between the output terminals of the first and second servo amplifier circuits 21A and 21B. And output resistance element 12
And servo induction coil means 8, 9 for the first and second
By applying the electromagnetic induction servo force for suppressing the displacement of the vibration-sensing member 4 to the displacement portion by the positive-phase servo signal and the negative-phase servo signal output from the servo amplifier circuits 21A and 21B, Control the vibration of the second vibration within a minute range, and at the same time, from the output resistance element 12, a first vibration detection signal having a magnitude and a phase corresponding to the positive phase servo signal and a magnitude and a phase corresponding to the negative phase servo signal. The two vibration detection signals are sent to the first and second signal transmission lines T1 and T2, respectively.

[Action]

The displacement detection signals obtained from the displacement detectors 6 and 7 are the first and second displacement detection signals.
In the servo amplifier circuits 21A and 21B, the servo amplifier circuits 21A and 21B are converted into a positive phase servo signal amplified in the same phase and a negative phase servo signal amplified in the inverted phase and fed back to the servo induction coil means 8 and 9, so that When the vibration of the vibrating member 4 is controlled within a minute range, even if noise is externally given by electromagnetic induction, the influence thereof can be further reduced.
At the same time, the positive-phase and negative-phase servo signals that have passed through the servo induction coil means 8 and 9 pass through the output resistance element 12 to generate the first and second vibration detection signals having the corresponding magnitude and phase, respectively. The signals can be sent to the first and second signal transmission lines T1 and T2, respectively, so that even if external noise is externally applied to the first and second signal transmission lines by electromagnetic induction, the influence thereof is further enhanced. Can be reduced.

〔Example〕

 An embodiment of the present invention will be described in detail below with reference to the drawings.

In FIG. 1 in which parts corresponding to those in FIG. 2 are designated by the same reference numerals, 20 indicates a servo type vibration pickup as a whole, and a balanced type servo amplifier circuit 21 is used instead of the unbalanced type servo amplifier circuit 11. Have.

The servo amplifier circuit 21 receives the output voltage of the position detector 6 and outputs a differential output voltage (that is, a positive phase servo signal having the same phase and a negative phase servo signal having the inverted phase) with a predetermined gain. Two amplifier circuits 21A and 2
The servo induction coil 9 and the output resistance element 12 are connected in series between the output terminals of the amplifier circuits 21A and 21B.

Thus, in accordance with the output voltage of the position detector 6, the amplifier circuits 21A and 21B are passed through the servo induction coil 9 and the output resistance element 12.
A drive current, which is a combination of the positive-phase servo signal and the negative-phase servo signal, circulates between them, and as a result, a suppressing force for the displacement of the vibration-sensing member 4 can be obtained.

Further, the output resistance element 12 is connected to the output terminals T1 and T2 while being insulated from the ground line, and the output terminals T1 and T2 are
Besides, a ground terminal TE is provided.

Therefore, at the output terminals T1 and T2, the two output voltages, which are in antiphase with each other and are proportional to the acceleration, are used as the first vibration detection signal and antiphase servo signal corresponding to the positive phase servo signal between the earth line and the ground line. Whereas it can be obtained as the corresponding second vibration detection signal, the output signals of opposite phases obtained at each output terminal T1 and T2 are connected to two signal transmission lines for transmitting to the measuring instrument body. External noise due to electromagnetic induction occurs as noise components in phase with each other.

Therefore, when measuring the balanced outputs of the output terminals T1 and T2 with the measuring instrument main body, if the in-phase noise components generated in the two signal transmission lines are equal in value to each other, the two signal transmission lines Since a voltage difference is not generated between the two connection points of the measuring instrument body and the connection terminal of the measuring instrument body, noise signals in phase with each other that are superimposed on the signal transmission line between the measuring instrument body and the servo type vibration pick-up 20 concerned. It is possible to reduce the influence of the above, and it is possible to reduce the mixing of the external noise into the servo loop.

In practice, most of the external noise that is mixed in the servo loop is the one that is mixed in via the signal transmission line due to electromagnetic induction, and the measured output signal is converted to a balanced output signal and output to the measuring instrument body. By reducing the influence of the noise signal superimposed on the transmission line, the SN ratio of the measurement output signal can be improved accordingly.

Further in this embodiment, two amplifier circuits 21A and 2
Since the balanced servo amplifier circuit 21 composed of 1B is used to output the measured output signal of the balanced output by configuring the servo loop, the servo circuit operates as a servo amplifier 21A. And the signal level of self-noise output from 21B can be reduced.

In practice, if the output amplifier circuit is connected to the non-earth side end of the output resistance element 12 in order to simply output the measured output signal as the balanced output, the measured output signal of the balanced output is output,
Although it is possible to prevent a decrease in the SN ratio of the measurement output signal due to the influence of external noise, a decrease in the SN ratio of the measurement output signal cannot be avoided due to the influence of the self-noise output from the output amplifier circuit.

In the case of this embodiment, according to the experiment, the output amplifier circuit is connected to the non-earth side end of the output resistance element 12 in order to simply output the measured output signal as the balanced output, and the measured output signal of the balanced output is output. Compared to the case, the signal level of the self-noise output from the servo amplification circuit 21 could be reduced to about 1/1000 of the self-noise output from the output amplification circuit.

Thus, by forming a servo loop using the balanced servo amplifier circuit 21 and outputting a measured output signal of the balanced output, when the signal level of the measured output signal is particularly low, that is, a low-level vibration is measured. Even when applied to a meter, the SN ratio of the measured output signal can be sufficiently improved.

By the way, the servo amplifier circuit 21 outputs a differential output voltage based on the output voltage of the position detector 6 to drive the servo induction coil 9, thereby converting the measurement output signal into a balanced output signal and measuring instrument. Configure a conversion circuit that outputs to the main body.

When the case 2 vibrates in the above configuration, the vibration sensing member 4 is displaced with respect to the position detection unit 6. As a result, the position detector 6, the electrode 7, the servo amplifier circuit 21, the servo induction coil 9,
A servo mechanism constituted by the magnetic circuit 10 and the output resistance element 12 operates to give a restraining force for controlling the displacement of the vibration-sensing member 4 within a minute range.

At this time, the drive current of the servo induction coil 9 is the output resistance element.
By being output as the terminal voltage of 12, the vibration sensing member 4
It is possible to detect the acceleration applied to, and thus it is possible to measure the vibration amount of the measured object to which the case 2 is attached.

At this time, the detection voltages generated at the terminals T1 and T2 by the drive current at the terminals T1 and T2 are in opposite phase, while the external noises are in phase with each other, and the vibration amount is detected based on the potential difference of the terminal voltage. By doing so, it is possible to obtain a measurement output signal having a high SN ratio with respect to the external noise.

According to the configuration of FIG. 1, by converting the measured output signals into balanced output signals having opposite phases and outputting the balanced output signals, even if external noise is mixed in via the signal transmission line, the influence of the external noise can be reduced. The vibration level can be measured without receiving.

Therefore, even if a long signal transmission line is installed in an environment where there is a lot of noise due to electromagnetic induction, a low level vibration detection signal can be accurately obtained.

Further, the signal level of noise generated inside the servo amplifier can be reduced, and the vibration detection signal at a much lower level can be measured more accurately by that amount. In addition, in the above-mentioned embodiment, the case where the present invention is applied to the servo type signal system in which the servo induction coil 9 is attached to the vibration sensing member 4 type has been described, but the present invention is not limited to this.
The servo coil may be fixed to the case side and the magnetic circuit may be provided on the vibration sensitive member side.

Further, in the above-mentioned embodiment, the case where the electrostatic type position detection unit is used is described, but the position detection unit is not limited to this,
For example, it can be widely applied when an optical or magnetic position detection mechanism is used.

As described above, according to the present invention, the positive and negative phase servo signals are formed in the first and second servo amplifier circuits based on the displacement detection signal of the displacement detection unit, and the servo signals are generated by the servo induction. By giving the coil means and the resistance element to the coil, when noise is generated in the servo system and the signal transmission line by the electromagnetic induction, it can be canceled as noise between balanced signals, and as a result, the influence of noise Can be further reduced.

[Brief description of drawings]

FIG. 1 is a first diagram of a servo-type signal pickup according to the present invention.
FIG. 2 is a system diagram including a partial block diagram showing the embodiment of FIG. 2, and FIG. 2 is a system diagram showing a conventional servo-type signal pickup. 1, 20 ... Servo type vibration pick-up, 2 ... Case,
4 ... Vibration-sensing member, 6 ... Position detector, 9 ... Servo coil, 10 ... Magnetic circuit, 11, 21 ... Servo amplifier circuit, 12 ...
... Output resistance element.

Claims (1)

[Claims] 1. A displacement section having a spring and a vibration-sensing member for vibrating the vibration-sensing member according to vibration of an object to be measured; and displacement for detecting displacement of the vibration-sensing member and generating a displacement detection signal. A first detecting unit, which amplifies the displacement detection signal based on the displacement detection signal in its original phase and outputs it as a positive phase servo signal.
Servo amplifier circuit, a second servo amplifier circuit that amplifies the displacement detection signal based on the displacement detection signal in an inverted phase, and outputs as a reverse-phase servo signal; and the first and second servo amplifier circuits. A servo induction coil means and an output resistance element which are connected in series between the output ends of the servo induction coil means, the servo induction coil means including the positive phase servo signal and the reverse phase servo signal output from the first and second servo amplifier circuits. By applying an electromagnetic induction servo force that suppresses the displacement of the vibration-sensitive member to the displacement portion by the phase servo signal, the vibration of the vibration-sensitive member is controlled within a minute range, and at the same time, the output resistance element changes A first vibration detection signal having a magnitude and a phase corresponding to the positive phase servo signal and a second vibration detection signal having a magnitude and a phase corresponding to the negative phase servo signal are respectively provided. Servo vibrometer, characterized in that it sent to the first and second signal transmission lines.