SU1388585A1 - Device for measuring low-frequency oscillations of compressor plants - Google Patents

Abstract

The invention allows to increase the measurement accuracy. The device contains a piezo sensor 1, a charging amplifier 2, a low-pass filter 3, an attenuator 4, integrators 5.6, 18, high pass filters 7.15, 8.9, switches 10 , 11 rms detector 12, peak detector 13, information display unit 14, analog-to-digital converter 19 and indicator 20. The low and high frequencies are filtered directly in the charge field by switching on between the high frequency correction circuit amplifiers having capacitive the input is entered in front of the integrators to eliminate shifts of zero integrator excitation levels at low frequencies. To reduce the error, the thermal compensation circuits are introduced into the rms detector. As a piezo sensor, a ring differential piezo element with a grounded midpoint is used. 1 ZoPo f-ly, 3 silt with (L

Description

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The invention relates to the field of measurement of oscillations, signaling and closure of compressors from surging „

The aim of the invention is to improve the measurement accuracy

FIG. 1 shows a block diagram of the proposed device; in fig. 2 is a charging amplifier circuit; FIG. 3 is a diagram of a rms detector.

The device contains a piezoelectric sensor 1, connected to a charging amplifier 2, a low-pass filter 3, an attenuator 4, the first 5 and second. 6 integrators, the first high-pass filter 7, the first 8 and second 9 amplifiers, the first 10 and the second 11. switches , rms detector 12, peak detector 13, information display unit 14, and a second high-pass filter 15.

In addition, the device contains a charge amplifier with correction circuits 16, a rms detector with thermal compensation circuits 17, 17, a third integrator 18, an analog-to-digital converter 19 and an indicator 2

The device works as follows

The signals of the piezo sensor 1 (Fig. 1) are fed to a charging amplifier 2 ". To reduce the level of interference and reduce sensitivity to transverse oscillations, the piezo sensor is made in the form of two rings of piezoceramic pasted on a metal ring with concentric grooves with a mass distributed around the outer circumference of the ring about

The signals from the ring plates are symmetrically fed to the input operational amplifier (Fig. 2), covered by negative feedback, and then to the second and third amplification stages, with correction circuits 16 being enabled between the output of the second stage and the inputs of the first stage, allowing filtering low and high frequencies directly in a charging amplifier. This reduces the level of electromagnetic interference and low-frequency noise of the piezo sensor.

From the output of the charge amplifier, which is structurally placed in a single package. With a piezo sensor, the signals through the connecting cable arrive at a low-pass filter 3, which forms the amplitude-frequency characteristic 5

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tic in the high-frequency range, and from the output of the filter arrive at the attenuator 4, providing the required signal attenuation, if necessary. From the output of the attenuator 4, the signal is successively fed to the first high-pass filter 7, the first integrator 5, the second high-pass filter 15 and the second integrator 6. A cascade of high-pass filters having a capacitive input is inserted in front of the integrators to eliminate shifts of zero integrator excitation levels at low frequencies From the outputs of the first and second integrators, signals proportional to vibration velocity and vibration displacement, respectively, are fed to the first and second amplifiers 8, 9, which serve for normalization (scaling ) Amplification From the outputs of the first and second amplifiers the signal is fed through the first switch 10, which selects

mode of operation (vibration velocity or vibration), and through the second switch 11, which selects the measurement mode (rms or peak), passes to the input of either the rms detector 12 or the input of the peak detector 13.

In order to reduce the error, thermal compensation circuit 17 (Fig. 3) is introduced into the rms detector. From the outputs of the RMS and peak detectors, the signal goes to the third integrator 18, which is used to select the averaging time of the indicator 20, which contains the dial instrument and the digital pointer, and the signal to the latter is fed through the analog-to-digital converter 19.

Claims (1)

1. Device for measuring low-frequency oscillations of compressor installations, containing a piezo sensor, connected to a charging amplifier, low pass filter, attenuator, first and second integrators, first high pass filter, first and second amplifiers, first and second switches, rms and peak detectors and also a display unit of information, characterized in that, in order to improve the measurement accuracy, it additionally contains a second high-pass filter, correction circuits, as well as a thermal compensation circuit, Connected to the RMS detector, the low-pass filter is connected to the charge amplifier and the output to the attenuator, the first high-pass filter is connected to the attenuator and the output to the first integrator, the second high-pass filter is connected to the first integrator, and output - to the second integrator, the outputs of the first and second integrators are connected to the corresponding user interface. 4ZJJ-CIH / faSn opo mu / ge / u- / tyuchpr / g directly to the first and second amplifiers, the outputs of the latter are connected to the first switch connected to the second switch, the inputs of the RMS and peak detectors are connected to the second switch, and the outputs are connected to the display unit, and the correction circuits are connected to a charging amplifier, 2 o Device according to claim 1, characterized in that an annular differential piezotlement with a grounded midpoint is used as a piezo sensor.  / Tb / ggri ifaemb / TrS CfJa.2 ama5pa-  Vf / ffpM.