RU2536097C1 - Vibration meter - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: vibration meter comprises a vibration converter, a parallel RC-circuit, the first operational amplifier, the first and second resistive dividers. To achieve the technical result, the second operational amplifier, the first, second and third capacitors, the serial RC-circuit, the resistor, the first, second and third diodes, the circuit of back-to-back diodes, an integrating circuit are introduced, being connected in accordance with the circuit on fig. 1.

EFFECT: expansion of functional capabilities during minimisation of a number of serially connected cascades.

3 cl, 3 dwg

Description

The vibration meter belongs to the information-measuring technique and can be used in control and signaling equipment for measuring vibration acceleration and vibration velocity.

Known passive linear detector of effective Bowke values (see LI Volgin "Linear electrical converters for measuring instruments and systems", M., Sov. Radio, 1971, p.166, Fig. 3.15b), containing a diode bridge, inputs which are connected to the signal source, and the outputs to a resistive divider, consisting of unequal resistances, to the output of which a capacitor is connected. With known ratios of resistors 4: 1, the function of determining the effective value is performed.

The disadvantages of the known linear detector of effective values are:

- performing only the function of a linear detector of effective values, which limits its functionality for measuring vibration, because there is no peak detector function;

- the lack of an adjustable amplifier with high input impedance, a bandpass filter;

- work with high-voltage signals (has a low sensitivity), because voltage losses on two bridge diodes are 1.5 V;

- the presence of a high error due to uncompensated temperature dependence of the characteristics of the diodes.

A well-known second-order filter Sullen-Key on the voltage follower (see P. Gareth "Analog devices for microprocessors and microcomputers", M., Mir, 1981, p. 71, Fig.3.16a), containing an operational amplifier, the non-inverting input of which connected through two series-connected resistors with equal resistances to the signal source, the combining point of the resistors is connected to the output of the operational amplifier through a capacitor, the non-inverting input of the operational amplifier (op-amp) is connected to a common bus through another capacitor. The filter provides high input impedance up to the cutoff frequency.

The disadvantages of the known low-pass filter (LPF) are:

- performing only the low-pass filtering function, which limits its functionality for measuring vibration. The filter does not have the ability to select the voltage gain while maintaining the requirements for the equality of resistors and the ratio of capacitors 2: 1;

- the filter is not a detector, the order of filter 2 due to the inclusion of another capacitor to the output of the op-amp, and for measuring vibration should be ≈3, does not perform the function of a band-pass filter on one operational amplifier.

A known vibration meter (see V.P. Maksimov and others. "Measurement, processing and analysis of rapidly changing processes in machines", M., Mechanical Engineering, 1987, p.47, Fig.1.15a), b)), containing a vibration transducer, connected to series-connected stages: matching voltage amplifier, band-pass filter, detector and averaging device.

The disadvantages of the known vibration meter are the complexity and cumbersomeness due to the presence of a large number of series-connected cascades, each of which contains one or two operational amplifiers and the cumulative error as the number of consecutive stages increases.

The closest in technical essence to the proposed invention is a vibration meter (R. Graf "Electronic circuits. 1300 examples", M., Mir, 1989, p. 88, Fig. 9.4), containing a vibration transducer, the output of which is connected through the first resistive divider to a common bus and is connected to a non-inverting input of the operational amplifier, the output of which is connected through a second resistive divider to the midpoint of the first resistive divider. The midpoint of the second resistive divider is connected through a parallel RC circuit to the inverting input of the operational amplifier.

The disadvantages of the known vibration meter are the limited functionality for measuring vibration due to the lack of functions of a band-pass filter and a detector of effective or peak values, because in coordination with the vibration transducer, only the function of ensuring a high input resistance and voltage amplification by a non-inverting amplifier is performed.

The technical result to which the invention is directed is to expand the functionality to the level of a meter of effective or peak vibration values while minimizing the number of cascades connected in series. This is achieved by combining the well-known function of a non-inverting amplifier with a high input impedance with a new function: a band-pass filter and a linear detector of effective or peak values.

To achieve a technical result in a vibration meter containing a vibration transducer, a parallel RC circuit, the input of which is connected to the inverting input of the first operational amplifier, the non-inverting input of which is connected to the first output of the first resistive divider, the second resistive divider, new is that an additional serial RC -chain, second operational amplifier, first, second and third capacitors, resistor, first, second and third diodes, circuit of parallel-parallel diodes, in an integrating circuit, the common output of which is connected to a common bus, which is connected to the non-inverting input of the second operational amplifier, through a serial RC circuit with an inverting input of the first operational amplifier, through the first capacitor with the first output of the first resistive divider, through a resistor with the second output of the first resistive divider and with the first output of the vibration transducer, the second output of which through the second capacitor is connected to the second output of the first resistive divider, the midpoint of which is through the resistor is connected to the input of a parallel RC circuit, the output of which is connected to the first terminals of the second resistive divider and the counter-parallel-connected diodes circuit, the second terminal of which is connected to the output of the first operational amplifier and to the anode of the first diode, the cathode of which is connected to the input of the integrating circuit, by the second the output of the second resistive divider and the cathode of the second diode, the anode of which is connected to the cathode of the third diode and the output of the second operational amplifier, the inverting input of which is connected to the anode of the third diode and a second middle point of the resistive divider.

The integrating circuit is made on an integrating RC circuit, and the effective value of vibration is measured.

The integrating circuit is made on the capacitor (for example, by shorting the terminals of the resistor of the integrating RC circuit or eliminating it), while the peak value of vibration is measured.

The expanded functionality of the vibration meter is provided by additionally introduced elements and links, due to which the well-known function of a non-inverting operational amplifier (high input impedance and adjustable gain on one operational amplifier) is combined with a new function: a band-pass filter and a linear detector of effective or peak values. Moreover, the steepness of the decay of the upper frequencies of the band-pass filter of the vibration meter corresponds to the third-order low-pass filter (for the second analog of the second-order low-pass filter) due to the new connection point of the output of the parallel RC circuit in addition to the first and third capacitors. The steepness of the low-pass decay of the band-pass filter corresponds to a second-order high-pass filter (HPF) due to the combined action of a new serial RC circuit and a second capacitor. The second output of the on-parallel-bandpass filter diode circuit on the first operational amplifier provides an integrating circuit (averaging device) of a linear detector of effective or peak values on the first and second operational amplifiers with its diodes with the required voltages eliminates the loss and error of passive diodes. The characteristic of the first operational amplifier with a circuit of counter-parallel connected diodes provides compensation for the direct voltage drop on the first diode, high sensitivity and accuracy, because opposite to the characteristic of the first diode.

Figure 1 presents an example implementation of a vibration meter, figure 2 shows the amplitude-frequency characteristic (AFC) of its band-pass filter. Figure 3 shows the voltage diagrams at the output of the vibration transducer and at the input and output of the integrating circuit.

The vibration meter (figure 1) contains a vibration transducer 1, a parallel RC circuit 2, a first operational amplifier 3, a first 4 and a second 5 resistive dividers, a second operational amplifier 6, a first 7, a second 8 and a third 9 capacitors, a serial RC circuit 10 , a resistor 11, a first 12, a second 13 and a third 14 diodes, a circuit 15 of counter-parallel connected diodes, an integrating circuit 16.

The input of the parallel RC circuit 2 is connected to the inverting input of the first operational amplifier 3, the non-inverting input of which is connected to the first output of the first resistive divider 4. The common output of the integrating circuit 16 is connected to a common bus. The common bus is connected to the non-inverting input of the second operational amplifier 6, through a serial RC circuit 10 with an inverting input of the first operational amplifier 3, through the first capacitor 7 with the first output of the first resistive divider 4, through the resistor 11 with the second output of the first resistive divider 4 and with the first the output of the vibration transducer 1. The second output of the vibration transducer 1 through the second capacitor 8 is connected to the second output of the first resistive divider 4, the midpoint of which through the third capacitor 9 is connected to Odom parallel RC-circuit 2. Yield parallel RC-circuit 2 is connected to first terminals of second resistor 5 and the divider circuit 15 included in antiparallel diodes. The second output of the anti-parallel-connected diodes circuit 15 is connected to the output of the first operational amplifier 3 and to the anode of the first diode 12. The cathode of the first diode 12 is connected to the input of the integrating circuit 16, the second output of the second resistive divider 5 and the cathode of the second diode 13. Anode of the second diode 13 connected to the cathode of the third diode 14 and the output of the second operational amplifier 6. The inverting input of the second operational amplifier 6 is connected to the anode of the third diode 14 and the midpoint of the second resistive divider 5.

Parallel RC circuit 2 is made on the resistor 17 and the capacitor 18.

The integrating circuit 16 can be performed on an integrating RC circuit: a capacitor 19 and a resistor 20 or on a capacitor 19 (for example, by shorting the terminals of the resistor 20 of the integrating RC circuit, see points a and b in figure 1, or its exception).

The second resistive divider 5 is made on series-connected resistors 21, 22.

The serial RC circuit is made on the resistor 23 and the capacitor 24.

The vibration meter (see figure 1) can be performed on operational amplifiers 544UD14, 544UD7, precision resistors P1-16, precision capacitors K10-43v and other capacitors such as K53-56.

The vibration meter works as follows.

(как у неинвертирующего усилителя).In fact, the claimed vibration meter is a filter amplifier linear detector of effective or peak value, depending on the implementation of the integrating circuit 16: on the integrating RC circuit (resistor 20, capacitor 19) or capacitor 19, respectively. An effective linear or peak value filter amplifier has a gain of 16 dB. Resistor 17 with resistance R17 and capacitor 18 are elements of a parallel RC circuit 2, resistor 23 has resistance R23 <R17. The gain in the passband is $$\left(\mathrm{one}+\frac{R17}{R23}\right)$$

(like a non-inverting amplifier).

In the initial static state, the output of the vibration transducer 1 is zero voltage, which corresponds to zero voltage at the output of the integrating circuit 16 in any design, because at the first output of the circuit 15 of the on-parallel-connected diodes, zero voltage due to its inclusion in the negative feedback circuit of the operational amplifier 3. At the output of the operational amplifier 3, the voltage is kept at the forward voltage level on the on-parallel-connected diodes of the circuit 15. It compensates for the voltage drop by diode 12, providing at its cathode and the output of the integrating circuit 16 zero voltage. The cathode of the diode 13 also has a zero voltage, as in the inverting operational amplifier (repeater) 6 included in the negative feedback circuit with zero input voltage.

When applying alternating voltage from the vibration transducer 1 (see U1 in Fig. 3), the process of amplifying it, highlighting a given band, and detecting with averaging over the level of the effective value when performing the integrating circuit 16 on the integrating RC circuit or over the peak value when performing the integrating circuit 16 on the capacitor 19. Scheme 15 counter-parallel connected diodes does not distort the frequency response of the bandpass filter of the vibration meter as a whole, but provides detection by the output of the integrating circuit 16 without errors.

до $$f_{ср}^{в}$$

(см. фиг.2) коэффициент усиления равен $$\left(1+\frac{R17}{R23}\right)$$

, как у неинвертирующего усилителя. Сопротивление согласования с вибропреобразователем 1 высокое, в полосе пропускания полосового фильтра равно сопротивлению резистора 11 (R11=5 МОм).The frequency response of the band-pass filter shown in figure 2, confirms the combination of the functions of the band-pass filter with high input impedance, amplification and detection, combined in a single device. In the passband of the bandpass filter from $$f_{\mathrm{from}R}^n$$

before $$f_{\mathrm{from}R}^{\mathrm{at}}$$

(see figure 2) the gain is $$\left(\mathrm{one}+\frac{R17}{R23}\right)$$

like a non-inverting amplifier. The coordination resistance with the vibration transducer 1 is high, in the passband of the band-pass filter is equal to the resistance of the resistor 11 (R11 = 5 MΩ).

, $$f_{ср}^{в}$$

на фиг.2) регулировку коэффициента усиления резистором 23 без изменения параметров резистивного делителя 4 и конденсаторов 9, 7 и 18 (плечи резистивного делителя 4 всегда равны, а соотношение конденсаторов 9, 7 равно 2 при любом усилении). Равенство плеч резистивного делителя 4 позволяет использовать цифровые потенциометры для регулировки верхней частоты среза (см. $$f_{ср}^{в}$$

на фиг.2) с помощью цифрового кода (кодоуправляемый фильтр). Конденсатор 18 параллельной RC-цепи 2 превращает его в ФНЧ третьего порядка. Вибропреобразователем 1 может быть пьезоакселерометр с нулевым смещением нуля или линейный акселерометр с ненулевым смещением нуля, конденсатор 8 разделительный, исключает постоянную составляющую с вибропреобразователя 1 и нижние частоты сигнала.At the cathodes of the combined diodes 12, 13 there is a half-wave rectification of the signals (see U13c in Fig. 3) with non-zero bias (see Ucm in Fig.3), confirming the function of the detectors. The output of the integrating RC circuit 16 (the point of combining of the resistor 20 and the capacitor 19 in Fig. 1) has an effective value (see U16eff = 0.707 · U13c in Fig. 3), confirming the linear detection function by the level of the effective value without errors, thanks circuit 15 counter-parallel connected diodes, diodes 12, 13 and the inequality of the time constants of the charging and discharge circuits. In this case, from the vibration transducer 1 (its equivalent), symmetrical signals centered by the capacitor 8 were applied: a sinusoidal voltage, a triangular sawtooth voltage, a meander, vibration, noise. At the output of the integrating circuit 16, executed on the capacitor 19, there is a peak value (see U16 peak = U13 in Fig. 3), confirming the linear detection function by the level of the peak value without errors, thanks to the compensating circuit 15 of counter-parallel connected diodes, diodes 12, 13. Without a parallel RC circuit 2, the bandpass filter circuit is similar to the Sallen-Key lowpass filter, but the feedback signal is not taken from the output of the operational amplifier 3, but from its inverting input. This provides an independent (does not change the cutoff frequencies, see $$f_{\mathrm{from}R}^n$$

, $$f_{\mathrm{from}R}^{\mathrm{at}}$$

figure 2) adjusting the gain of the resistor 23 without changing the parameters of the resistive divider 4 and capacitors 9, 7 and 18 (the shoulders of the resistive divider 4 are always equal, and the ratio of the capacitors 9, 7 is 2 for any gain). Equal shoulders of resistive divider 4 allows the use of digital potentiometers to adjust the upper cutoff frequency (see $$f_{\mathrm{from}R}^{\mathrm{at}}$$

figure 2) using a digital code (code-controlled filter). The capacitor 18 of the parallel RC circuit 2 turns it into a third-order low-pass filter. Vibration transducer 1 may be a piezo-accelerometer with zero zero offset or a linear accelerometer with non-zero zero bias, the capacitor 8 is isolating, eliminates the constant component from vibration transducer 1 and the lower frequencies of the signal.

The first stage on the operational amplifier 3 performs the functions of:

- amplification with a high input resistance, due to which Rin = R11;

- band-pass filter;

- compensating circuit 15 of the detector of the positive half-wave signal (compensating for the direct voltage drop across the diode 12);

- coordination with the resistive divider 5 of the detector of the negative half-wave signal on the inverting operational amplifier 6 with the detecting diode 13.

At the cathodes of the diodes 13 and 12 there is a total bias half-wave rectification of the amplitudes offset with respect to the zero level (see Ucm in Fig. 3) with an error in the opposite-parallel connected diodes of the circuit 15. When performing the integrating circuit 16 on the resistor 20 and the capacitor 19 using the resistor 22 and the inverting input of the operational amplifier 6, averaging is performed over the level of the effective value due to the inequality of the time constants when charging the capacitor 19 and its subsequent discharge. When performing the integrating circuit 16 on the capacitor 19, peak detection is performed.

.The expanded functionality of the vibration meter is provided by additionally introduced elements and links, due to which the well-known function of the non-inverting operational amplifier 3 (high input resistance and adjustable gain on one operational amplifier) is combined with a new function of the bandpass filter and the compensation circuit of a linear effective or peak detector. Moreover, the steepness of the decay of the upper frequencies of the band-pass filter corresponds to the third-order low-pass filter due to the capacitor 18 from the parallel RC circuit 2 and capacitors 7, 9. The steepness of the decay of the lower frequencies of the band-pass filter corresponds to the second-order high-pass filter due to the combined action of the capacitors 8, 24. parallel connected diodes provides the integrating circuit 16 with the necessary voltages, eliminates the loss and error of the diode 12 and ensures error-free operation of the band-pass filter. The characteristic of the first operational amplifier 3 with a counter-parallel-connected diode circuit 15 is opposite to that of the diode 12, which compensates for the direct voltage drop across the diode 12. The diode 14 provides an unsaturated mode of operation of the operational amplifier 6 for the positive half-wave of the signal and participates in the effective value averaging circuit. The time constants of the charging and discharge circuits of the linear detector of the effective value are not equal and are selected so that the constant component of the voltage across the capacitor 19 of the integrating RC circuit is equal to the effective value. For example, for sinusoidal voltage and normal noise, the ratio $$\frac{R\mathrm{twenty}+R22}{R\mathrm{twenty}}=2.5$$

.

Due to this, when calibrating at a sinusoidal voltage and then measuring the effective value of the triangular voltage, meander voltage, vibration or noise, there will be no error. A constant component equal to the effective or peak value of vibration with the corresponding design of the integrating circuit 16 is allocated on the capacitor 19.

Tests of the vibration meter mock-up performed on quadruple operational amplifiers of the 564UD14 type and simulation of the vibration meter in the Micro-Cap 7.1.0 CAD system confirmed its operability and claimed advantages in the operating temperature range from -40 to + 50 ° C.

Claims (3)

1. A vibration meter containing a vibration transducer parallel to the RC circuit, the input of which is connected to the inverting input of the first operational amplifier, the non-inverting input of which is connected to the first output of the first resistive divider, the second resistive divider, characterized in that the serial RC circuit is additionally introduced, the second operational amplifier, first, second and third capacitors, resistor, first, second and third diodes, a circuit of counter-parallel connected diodes, an integrating circuit, the common output of which is dinene with a common bus, which is connected to the non-inverting input of the second operational amplifier, through a serial RC circuit with an inverting input of the first operational amplifier, through the first capacitor with the first output of the first resistive divider, through the resistor with the second output of the first resistive divider and with the first output of the vibration transducer, the second terminal of which through the second capacitor is connected to the second terminal of the first resistive divider, the midpoint of which through the third capacitor is connected to the steam input allelic RC-circuit, the output of which is connected to the first terminals of the second resistive divider and the counter-parallel diode circuit, the second terminal of which is connected to the output of the first operational amplifier and the anode of the first diode, the cathode of which is connected to the input of the integrating circuit, the second terminal of the second resistive divider and the cathode of the second diode, the anode of which is connected to the cathode of the third diode and the output of the second operational amplifier, the inverting input of which is connected to the anode of the third diode and the midpoint of the second cut a stylish divider. 2. The vibration meter according to claim 1, characterized in that the integrating circuit is made on an RC circuit. 3. The vibration meter according to claim 1, characterized in that the integrating circuit is made on a capacitor.

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