RU2558636C2 - Vibration detector with element of digital calibration - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: vibration detector with a digital calibration element is made in the form of a metal body with a flange for fixation on a controlled object. Inside the sensor body there is a primary piezoceramic converter and an electronic circuit of primary converter coupling. At the same time the electronic circuit of a signal amplification tract comprises a digital potentiometer, making it possible to return sensor transformation ratio to the initial value. The potentiometer is controlled from an outer block of reference pulses, supplied via a process slot in the sensor body during calibration in the setting mode on a vibration test bench of sample values of vibration speed at base frequency and fixation of the sensor output signal on a regular load of a registration unit.

EFFECT: maintenance of vibration detector passport characteristics during entire operation time.

4 dwg

Description

The invention relates to measuring equipment and may find application in the vibration diagnostics of various technological equipment - turbine units, oil and gas pumps, compressors, wheelsets of high-speed railway transport.

Known serial industrial designs of vibration transducers: VK-310, HS-421 Series Vibration sensor, vibration velocity sensor 9842V, “Measuring unit for carriage axles” - Patent RU No. 2360817, 2009 - analogues. To ensure constructive manufacturability, the sensors are made in the form of a housing with a flange, a piezoceramic sensitive element and an electronic interface circuit located on a printed circuit board that is rigidly fixed in the sensor housing are placed inside the sensor housing.

The disadvantages of analogues include the inability to calibrate the sensor during aging of the piezoelectric ceramic sensor due to the loss of quality during the period of operation while maintaining the original value of the conversion coefficient. Existing vibration velocity sensors during their periodic calibration determine new values of the conversion coefficient, which differ from the initial values established in the manufacture of sensors. Such calibration requires the introduction of new conversion factors for sensors in the data acquisition system, which creates additional difficulties during operation.

The well-known “System for monitoring the condition of carriage axle boxes” (Patent RU No. 2356771, 2009). The analogue system includes a set of primary sensors installed in a standard axle box mounting unit operating in the mode of discrete sequential measurements of temperature and vibration overload of a two-parameter sensor via one two-wire power line by simultaneously reversing the power supply of all sensors, as well as a diagnostic mode by programmatically processing signals in the functional paths of temperature measurement and vibration overloads and software activation of a three-color LED alarm in the car block and signaling by creating a current measuring circuit of each sensor and introducing a power polarity reversal unit, an analog-to-digital converter included in the output of the measuring circuit of each sensor, a buffer storage device for the data of current measurements of signals in the measuring circuits, connected to the controller input, the output of which connected to the input of the alarm unit.

The disadvantages of the analogue include:

- loss of quality factor (conversion coefficient) of piezoelectric sensors during the service life;

- the need to calibrate the measuring path of each sensor in the interests of an automated program for processing the condition of carriage pairs in specialized processing centers (at the end of flights) according to the recording of measurement information in buffer storage devices.

The closest analogue to the claimed technical solution is the “Test stand calibration of vibration transducer [see Operation manual 4277-032-98222904 RE, ViKont LLC, Fig. 4, p.18, Moscow, 2010, OKP 427734] ”is the closest analogue.

The calibration test bench determines the value of the conversion coefficient of the vibration sensor at a base frequency of 45 Hz and the nonlinearity of the amplitude characteristic in the operating frequency range by comparing them with the values of the (reference) reference vibration transducer.

The test bench for calibrating the vibration transducer of the closest analogue contains an electrodynamic vibrator on which a calibrated and model vibration sensors are installed, a power amplifier with a control unit for setting reference vibration parameters measured by a laser vibrometer, measuring channels for recording signal parameters of a calibrated and model vibration transducers.

According to the results of verification measurements, the degree of sensitivity loss of the calibrated vibration sensor is estimated by calculating the nonlinearity of the amplitude and frequency characteristics.

The calculation of the non-linearity of the AX vibration converter in the operating range of vibration velocity or vibration acceleration at the base frequency is carried out according to the formula:

,

,

- среднее арифметическое значение коэффициента преобразования.Where $${\overline{K}}_{PR}=\frac{\mathrm{one}}{n}\sum _{i=\mathrm{one}}^n{K}_{PRi}$$

- the arithmetic mean value of the conversion coefficient.

The calculation of the frequency response unevenness is made according to the formula:

,

,

where K _{CR fi} is the conversion coefficient at the i-th frequency;

K _{pr base} - the conversion coefficient at a base frequency of 45 Hz.

The verification result is presented in the form of a table of values of deviations of the measured parameters from the readings of an exemplary vibration transducer.

The disadvantage of the closest analogue should be considered the need to recalculate the source data by the conversion coefficient of each sensor with automated software diagnosing the state of the controlled object and its components.

The problem solved by the claimed technical solution is to change the electronic circuit of the vibration sensor to be able to calibrate its output characteristics over the entire operating interval to the passport data obtained during the initial certification of the sensor.

The technical result is achieved in that the vibration sensor with a digital calibration element is made in the form of a metal housing with a flange for mounting on a controlled object, a primary piezoceramic transducer is placed inside the housing, an electronic circuit for connecting the primary transducer to the recording unit, characterized in that the electronic circuit includes a digital a potentiometer that allows you to return the conversion coefficient of the sensor to the initial value, controlled from an external block of reference pulses, p supplied through the terminals of the process connector in the sensor case during calibration in the mode of setting on the test vibrostender the standard values of vibration velocity at the base frequency equal to the weighted average frequency of the measured process of vibration of the object and the normal load mode of the recording unit.

The invention is illustrated by drawings, where

Fig 1 is an element-wise diagram of a vibration sensor;

figure 2 is a structural diagram of a block of reference pulses;

figure 3 - control signal of a digital potentiometer;

figure 4 - amplitude-frequency characteristic of the measured process.

An element-by-element diagram of the vibration sensor is illustrated in Fig. 1. The vibration sensor consists of a metal housing with a flange 1 for mounting the sensor, a primary piezoceramic transducer 2 is placed inside the housing, an electronic interface circuit 3 with a digital potentiometer 4, a process connector 5 with leads for connecting a measurement channel 6 for registering a vibration sensor signal and external generator 7 reference pulses.

The structural diagram of an external generator 7 of reference pulses (Fig. 2) contains a single vibrator 8 with protection against contact bounce, a toggle switch 9 for changing the values of a digital potentiometer, a clock button 10, a button 11 for recording values in the memory of a digital potentiometer, technological socket 5.

The control signal of the digital potentiometer during calibration is illustrated in Fig.3.

The dynamics of the interaction of elements during calibration is as follows. Preliminarily, according to the frequency response of the measured process of the calibrated sensor, the weighted average vibration frequency (F _cp ) of the controlled object is calculated from the condition:

.

.

The average frequency F _cp = 64 Hz divides the area under the curve, as illustrated in figure 4, in half. The frequency response of the vibration process is measured by connecting to the output of the registration block a spectrum analyzer of the 3560C type (see, http://tecon.com.ua/bruel-and-kjaer/107-product17.html). Then, the calibrated and reference sensors are mounted on a test vibration bench. The base frequency of the electrodynamic transducer of the stand is set equal to F _{cp of the} measured vibration process. Since all the cascades of the measuring path affect the output signal of the calibrated sensor, the measurements are carried out with connected recording units that simulate a reference load. An external reference pulse generator is connected to the calibrated sensor and the sensor conversion coefficient coincides with the passport data by changing the resistance value of the digital potentiometer.

All elements of the vibration sensor are made on the existing technical base of analogues. The new element is a digital potentiometer, made on the Maxim integrated circuit - MAX5128 [datasheets.maximintegrated.com/en/ds/MAX5128.pdf].

The effectiveness of the claimed technical solution is determined by the ability to provide passport characteristics of the vibration sensor during the entire period of its operation, as well as by the possibility of automated software signal processing in diagnosing vibration processes.

Claims (1)

The vibration sensor with the digital calibration element is made in the form of a metal case with a flange for mounting on a controlled object, a piezoelectric transducer is placed inside the case, an electronic circuit for pairing the primary transducer with the recording unit, characterized in that the electronic circuit includes a digital potentiometer, which allows you to return the conversion coefficient sensor to the initial value, controlled from an external block of reference pulses supplied through the terminals of the technological plug in the sensor housing during calibration in the task mode on the test vibrostender of standard values of vibration velocity at a base frequency equal to the weighted average frequency of the measured process of vibration of the object and the normal load mode of the recording unit.

Images