KR200255365Y1 - A charge type charging amplifier for acceleration sensor - Google Patents

Abstract

An electrostatic charge amplifier for an acceleration sensor is described. The charge type amplifier for an acceleration sensor of the present invention performs filtering on a signal transmitted from an acceleration sensor in a desired band and outputs a difference between the filtered signal and a reference signal to perform amplification, A charge interface unit for performing selective switching to adjust the size and frequency; A feedback resistor module connecting a plurality of resistors to each unit is connected between the input and output terminals of at least one OP-AMP to set the sensor sensitivity by selective switching, and the signal conversion is performed by the unit voltage value with respect to the unit acceleration value part; A gain control unit for performing selective switching at one terminal of each of at least one OP-AMP continuously combined to output a corresponding voltage value corresponding to the acceleration value, and outputting a corresponding gain value; A peak detector for converting a DC component into a DC component by rectifying and smoothing to output a maximum DC value from a signal output from the gain controller; And a transient input detecting unit for comparing the maximum DC value and the limit voltage value to determine whether the maximum DC value output from the peak detecting unit is within the measurement operation range, and a warning is made at a value higher than the limit voltage value. According to the present invention, not only is it possible to extend the versatility of the charge type charge amplifier by adjusting the input range according to the capacity of the accelerometer, or allowing the user to input and use it according to the sensitivity of the accelerometer, It is possible to know whether the input value is excessively inputted from the output signal value.

Description

[0001] The present invention relates to a charge type charging amplifier for an acceleration sensor,

The present invention relates to an electrostatic charge amplifier for an acceleration sensor, and in particular, it is possible to set an input range and an amplification range according to the capacity of an accelerometer, perform an acceleration sensor sensitivity (pC / g) input function, The present invention relates to an electrostatic charge amplifier for an accelerometer, which is capable of originally canceling noise generation for a signal and for detecting whether the signal is within a measurement range.

Sensors are the next generation wave of information technology. Many of the sensors are used in many places as cars and subways are the most used sensors for modern people, and many sensors are used all over the place. As a safer and more comfortable means of transportation, Holding. In particular, a great number of sensors are used in automobiles, and the number of sensors used in a luxury vehicle increases.

Especially, as the concern about the stability of automobiles has increased recently, the installation of airbags becomes a safety device for protecting the driver and passengers in the frontal collision, and the research on the acceleration sensor for automobile, which is a key element to enter the airbag, . In order to improve the stability, reliability, comfort, and convenience of the vehicle, the acceleration sensor is composed of an electronic engine control system, an ABS (anti-lock braking system), an intelligent suspension system, a steering system, auto-door lock system).

In this way, as the standard of living of residents increases, there is an increasing demand for acceleration sensors that detect vibration in a situation where there is a rapid increase in demand for products that are free of vibration and no sound. This acceleration sensor can be applied to the current semiconductor production technology, resulting in miniaturization, mass production, and cost reduction. Therefore, the application range is very wide in addition to the automobile market. Such as measuring instruments such as inclinometer, tilt meter, level, shock recorder, vibration sensor, etc., precision machines such as robots for factory automation, and inertial sensors such as acceleration sensors And is used in many fields such as a hand-held speedometer for preventing camera shake.

However, in order to increase the practicality of the acceleration sensor, four kinds of sensing characteristics, reliability, applicability, and productibility of the sensor must be considered at the same time so that the product can be rationally evaluated , Development of the actual high performance acceleration sensor is proceeding with IC and smartization, so it can not be thought of as the sensor part alone, and it should be considered as a comprehensive system. That is, the sensor unit, the amplification circuit unit, the interface unit, the microprocessor unit, and the actuator unit must be structured in the best condition. It is a very important issue to consider reliability, performance, and cost in a comprehensive system, and to decide where to integrate on-chip in relation to current technology level.

Thus, after sensing vibration and noise, reliable checking equipment for the sensed signal is essential. For example, in vibration and noise of automobiles, ships, bridges, harbors, factories and various household appliances, noise vibration prediction and measurement experiments in everyday life and industrial fields are generally performed by using a piezo-ceramic type sensor, which is essentially a charge amplifier that processes the sensed signal.

However, since the vibration measuring sensors and amplifiers currently used are mainly designed for measuring mechanical vibration, the reliability of the low frequency characteristics and signal reduction on the transmission line is not verified.

Therefore, the object of the present invention is to set the input range and the amplification range according to the capacity of the accelerometer in order to secure reliability according to the use of the charge type acceleration sensor having good signal characteristics for low frequency characteristics and signal reduction, pC / g) input function, and it is provided to provide an electrostatic charge amplifier for an accelerometer which can erase noise from a signal output from a sensor and informs whether the signal is within the measurement range.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view for schematically explaining the characteristics of a piezoelectric element,

2 is a simplified equivalent circuit of a circuit in which a piezoelectric acceleration sensor is connected to a charge amplifier,

3 shows a simplified equivalent circuit of a charge amplifier to which an accelerometer is connected,

4 shows an equivalent circuit of a charge amplifier to which an accelerometer is connected,

5 is an exponential decay graph with a time constant in a capacitor,

6 is an equivalent circuit diagram of an accelerometer coupled to an equivalent capacitor and a resistor,

7 is a graph showing the relationship between phase and amplification,

8 shows a model representing the internal noise source of the OP-AMP,

9 is a graph showing noise characteristics with respect to input power capacitance,

10 is a control circuit block diagram schematically showing the overall configuration of a charge amplifier according to an embodiment of the present invention;

11 is a specific circuit diagram of a charge amplifier according to an embodiment of the present invention,

12 is a circuit diagram specifically showing a charge interface of the charge amplifier,

13 is a circuit diagram specifically showing a normalization section of the charge amplifier,

14 is a circuit diagram specifically showing a gain control section of the charge amplifier,

15 is a circuit diagram specifically showing a peak detecting portion of the charge amplifier,

16 is a circuit diagram specifically showing a transient input detecting section of the charge amplifier.

Description of the Related Art [0002]

10: piezoelectric element 20: metal electrode

100: charge interface unit 110: constant power supply and filtering unit

120: comparison switch 130: ground signal generator

140: input signal size and frequency adjustment unit 200: standardization unit

210: sensor sensitivity setting unit 300: gain control unit

310: first gain control unit 320: second gain control unit

400: Peak detection part 410:

420: smoothing unit 500: transient input detecting unit

510: LED

According to an aspect of the present invention, there is provided an electrostatic charge amplifier for an acceleration sensor, wherein a desired band is filtered with respect to a signal transmitted from an acceleration sensor, a difference between the filtered signal and a reference signal is output, A charge interface unit for performing selective switching to adjust a magnitude and a frequency of the input signal; A feedback resistor module connecting a plurality of resistors to each unit is connected between the input and output terminals of at least one OP-AMP to set the sensor sensitivity by selective switching, and the signal conversion is performed by the unit voltage value with respect to the unit acceleration value part; A gain control unit for performing selective switching at one terminal of each of at least one OP-AMP continuously combined to output a corresponding voltage value corresponding to the acceleration value, and outputting a corresponding gain value; A peak detector for converting a DC component into a DC component by rectifying and smoothing to output a maximum DC value from a signal output from the gain controller; And a transient input detecting unit for making a warning at a value equal to or higher than a limit voltage value by comparing the maximum DC value with a limit voltage value to determine whether the maximum DC value outputted from the peak detecting unit is within a measurement operation range .

The charge interface unit may include a constant voltage supply and filtering unit that controls a DC component when a signal output from the acceleration sensor is input, generates a constant voltage, and passes a desired band signal; A ground signal generator for generating a reference signal which is an analog ground signal; A comparison switch for comparing the fine signal having passed through the constant voltage supply and filtering unit with a reference signal and outputting the difference; A first OP-AMP connected to a non-inverting terminal at one end of the comparing switch and having an inverting terminal connected to the other end of the comparing switch for performing signal amplification; And an input size selection switching unit for adjusting a feedback resistance value to adjust a magnitude of an input signal transmitted from the acceleration sensor, and an input size selection switching unit for selectively connecting the input size selection switching unit And a frequency selection switching unit. Here, the input size selection switch is connected to the output terminal of the first OP-AMP so that the sensitivity of the sensor is between 0.1 (pC / g) and 1 (pC / g) lt; RTI ID = 0.0 > pC / g) < / RTI > And a terminal connected to the frequency selection switching unit and discriminating the case where the sensitivity of the sensor is between 0.1 (pC / g) and 1 (pC / g) and between 1 (pC / g) The frequency selective switch includes a first switch for selectively connecting to a terminal for distinguishing a case where the required frequency response is between 0.1 Hz and 1 Hz and a case where the frequency response is between 1 Hz and 1 Hz, .

Also, the normalization unit may include: a second OP-AMP connected to the signal output from the first OP-AMP to amplify the signal output from the charge interface unit so as to be input to the non-inverting terminal and the inverting terminal to ground; A feedback resistor is connected between the output terminal of the second OP-AMP and the non-inverting terminal to set the sensitivity of the sensor, and at least one feedback resistor module connecting resistors having a plurality of different resistance values for each unit is connected And a sensor sensitivity setting section for performing selective switching in each feedback resistance module. Here, the resistance value of the resistance forming the sensor sensitivity setting unit preferably has an error value in the range of 0.1% to 1%.

The gain control unit includes a first gain control switch connected between the non-inverting terminal and the output terminal for inputting and outputting a signal having a plurality of gain values so that the fixed signal output from the normalizing unit can be input to the inverting terminal A first gain control unit comprising a third OP-AMP for connecting the first OP-AMP and the second OP-AMP; And a fourth OP-AMP connecting the output terminal of the third OP-AMP to the inverting terminal and connecting a second gain control switch capable of inputting / outputting a signal having a plurality of gain values between the non-inverting terminal and the output terminal 2 gain control unit.

The fifth OP-AMP includes a diode connected between the inverting terminal and the output terminal for rectifying the AC component to a DC component. A sixth OP-AMP having a non-inverting terminal connected to the rectifying diode at the output terminal of the fifth OP-AMP and having a diode rectifying an AC component to a DC component between the inverting terminal and the output terminal; And a smoothing unit connected to the rectifying diode at the output terminal of the sixth OP-AMP and smoothing the rectified signal.

The transient input detecting unit may include a comparator connected to allow the signal output from the peak detecting unit to be input to the non-inverting terminal, the limiting voltage of which is input to the inverting terminal by the dividing resistor to perform comparison; And a lighting means connected to the output terminal of the comparator for lighting at a voltage exceeding a limit voltage. At this time, the lighting means uses an LED.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a view for schematically explaining a characteristic of a piezoelectric element. FIG. As shown in FIG. 1, the piezoelectric acceleration sensor has an effect of converting the mechanical properties of the piezoelectric element 10 into electrical properties by connecting the metal electrodes 20 to both sides of the piezoelectric materials 10, . That is, when a force is applied to the direction of polarity of the piezoelectric element 10, electric charges are generated on both sides, and a potential difference therebetween is generated. This potential difference is proportional to the magnitude of the applied force, so that the accurate vibration amount can be measured. The same phenomenon occurs when compressing stress, tensile stress and shear stress are applied.

An electrostatic charge amplifier for an acceleration sensor, which is proposed in the present invention, is connected to an acceleration sensor composed of the piezoelectric element 10 as described above. The electrostatic charge amplifier for the acceleration sensor detects a high impedance output from the acceleration sensor, To-low-impedance signal suitable for direct transmission to the instrument. The charge amplifier for the charge sensor also performs the following functions. In other words, it performs the amplification of the vibration signal to match the output of the accelerometer with the input sensitivity of the measuring equipment, the sensitivity to the degree required by the whole system, and the acceleration signal integration function to obtain the velocity and displacement signal. It also performs an overload warning function for the input signal and the output signal, and performs a filtering function for eliminating unwanted signal noise.

The preamplifier used when using a piezoelectric accelerometer can be roughly classified into a charge type amplifier and a voltage type amplifier. Generally, voltage type sensors are used in many cases. However, when used for long distance measurement, the sensor is used in consideration of the fact that it is difficult to find the original signal due to signal reduction and noise on the line. In this case, The signal output from the typical sensor is solved using an electrostatic preamplifier. This electrostatic sensor has the advantage that the leakage on a single line is superior to the voltage type and can be used without adjusting the overall sensitivity of the special system.

The output voltage of the charge amplifier is linearly proportional to the amount of charge input, that is, the amount of change in the acceleration of the accelerometer. The amplification gain of the charge amplifier is controlled by a feedback capacitor connected in parallel to the OP-AMP. 2 is a diagram showing a circuit in which a piezoelectric acceleration sensor is connected to a charge amplifier by a simple equivalent circuit. As shown in FIG. 2, the accelerometer can be largely divided into a cable and a preamplifier. Where Rc is the resistance of the accelerometer, Cc is the capacitance of the cable and the connector, Rb is the resistance between the transmission line and the cable screen, Cp is the charge Rp is the input side resistance of the charge amplifier, Cf is the feedback capacitance, A is the gain of OP-AMP, and Vo is the voltage output of the charge amplifier.

In this case, since the path of the accelerometer, the charge amplifier, and the feedback generally have a very high resistance value, the equivalent circuit shown in FIG. 3 can be expressed by simplifying the circuit diagram shown in FIG. 3 is a simplified equivalent circuit of a charge amplifier to which an accelerometer is connected. 3, Ct = Ca + Cc + Cp, I is the total current from the accelerometer, Ii is the current flowing past Ct, Ic is the current flowing through the feedback path of OP-AMP, Vc is the feedback capacitance Respectively.

As shown in Fig. 3, there is the following relationship between the input voltage Vi and the output voltage Vo.

---------------------------------------------- (One)

Vc can be obtained as follows.

-------------- (2)

Ideal amplifiers have zero input current, so if you apply Kirchhoff's law,

------------------------------------------- (3)

Here, since the current I is related to the charge generation of the sensor (piezoelectric element), if the current is expressed using another expression,

----------------------------------------------- (4)

----------------------------- (5)

--------------------------------- (6)

If we recall the above equations to Kirkhoff's law, the current I generated through the accelerometer can be expressed as:

------------------------ (7)

The above equation can be interpreted through integration. Constants corresponding to the DC offset voltage present at the beginning of the amplifier output can be regarded as zero, and if the expression for Vo is established by taking advantage of the fact that such DC offsets disappear rapidly as the preamplifier operates,

------------------------------- (8)

Here, since the A value generally has a very large value (? 10 ⁵ )

-------------------------------------------- (9)

.

In an ideal case, the input voltage converges to A, which is the voltage gain, to infinity

----------------------------------------- (10)

. Eventually, the limited input resistance has no effect on the output voltage. This means that the current from the accelerometer and the current through the feedback capacitance Cf are equal in magnitude and the polarity is opposite. It can be seen that all currents are generated in the accelerometer and all go into the feedback capacitance.

Using these results, a simpler and simpler equivalent circuit can be obtained as shown in FIG.

If we summarize the expressions so far

---------- (11)

Can be obtained.

This equation is difficult to be interpreted by using only simple integrations as shown in FIG. 3, but the following equations can be obtained if it is assumed that the DC component and the initial conditions disappearing in a short time can be ignored in the analysis.

--------------- (12)

The value of Vo obtained by rearranging this is

--------------------- (13)

, Where A and Rf have very large values.

------------------------------------------------ (14 )

.

If Rf has a definite value, the following equation can finally be obtained.

------------------------------------- (15)

It can be seen from the above equation that the output voltage Vo is proportional to the output charge Qa generated by the accelerometer and can be controlled through the capacitance Cf of the feedback path in the charge amplifier.

The low-frequency response of the charge amplifier is determined by the time constant set by the feedback circuit around the OP-AMP. And this is not affected by changes in the resistive input load. As a result, the lowest limit frequency is changed by the change of the feedback resistance.

An accelerometer is a device that generates a signal by itself. Therefore, the generated signal does not have a DC component. So from a physics point of view, you can not get any power without any external power input. Even if a static force is applied to the piezo element, no power is supplied.

To understand the low-frequency characteristics of the charge amplifier, it is necessary to understand a simple RC network circuit.

A capacitor is a device for charging a charge. The capacitance of the capacitor is determined by the amount of charge that is negated when a unit voltage is applied to the capacitor. If we summarize the formula for this

.

Assuming that the ideal capacitor is charged with Vo and assuming it is an ideal capacitor even though the insulated resistance of the capacitor is finite, ) Will decrease by plotting the exponential function. This is well illustrated in FIG.

When measuring a sinusoidal signal, this time constant ( ) Have more significance. Here, ) Affects the low frequency phenomenon of the system.

6 is an equivalent circuit diagram of an accelerometer connected to an equivalent capacitor and a resistor.

6 into Equation

------------------------------- (16)

, And if the current and voltage are assumed to be harmonic functions

----------------------- (17)

Here, the magnitude of the voltage And phase Is as follows.

------------------ (18)

here = 1, tan = 1 = 45 [deg.]. And, . This is well illustrated in FIG. 7, where the relationship between the phase and the amplitude between the input and the output is expressed as an equation, = 1 (i.e., 2 fRC = 1)

----------------------------------- (19)

.

Here, f ₁ is generally referred to as a LLF (Low Limiting Frequency), and the phase shifts by 45 ° when the output level drops by 3 dB.

As noted above, the lowest limit frequency is the time constant of the feedback circuit ( = RC). The phase difference between the input and the output is typically 180 ° (-A) and is delayed by 45 ° at the lowest limit frequency.

From the above equation (13)

------------------------ (20)

As can be seen also, the minimum limiting frequency can not be changed until the resistive input load changes by Rf / A. This is because Cf and Ct imposed on the circuit have similar dimensions as shown in the formula. As a result, the influence of the input load can be reduced by adjusting the gain A, which is an influencing factor, so that the lowest limit frequency can be adjusted by Rf. Where Rf is the feedback resistance and -A is the gain.

The use of a remote accelerating cable and the use of low amplification settings in the equipment reduces the signal-to-noise ratio in the measurement by increasing the noise in the charge amplifier. If the resistive load drops significantly on the input side, the noise also increases.

8 is a model expressing the internal noise source of the OP-AMP. As shown in Figure 8, all of the noise inside the amplifier is represented by the power source and the current source of the input. This equivalent circuit does not include external noise effects such as triboelectricity, ground deflection voltage, electromagnet effect in cable.

Where Zt is the equivalent impedance of the accelerometer and cable, Zf is the equivalent impedance of the feedback path, e _n is the noise voltage, i _n is the noise current, and Vo is the output voltage.

As described above, there is a virtual ground on the inverting input side of the OP-AMP, and no current flows. therefore

------------------------------------ (21)

------------------------------------------ (22)

.

If we replace the above expression with the expression for the source signal

---------------------------------------- (23)

.

In the above equation, the impedances Zt and Zf are the capacitance components of the main component within the frequency range,

------------------------------------------------- ( 24)

here

---------------------------------------- (25)

ego

----------------------------------------- (26)

.

In addition, this can be converted to equivalent charge noise qt,

----------------------------------- (27)

Lt; / RTI >

This shows that as the charge noise increases, Ct and Cf increase together so that the sensitivity or the lowest limiting frequency is not changed by capacitive load or resistive load. However, when using very long distances, a reduction in the signal-to-noise ratio is inevitable.

9 is a graph showing noise characteristics with respect to input power capacitance. As shown in FIG. 9, when Cf (feedback capacitance) is used to determine the gain of the amplifier, it is necessary to set to a large noise and a low gain, which requires a high feedback capacitance. The use of accelerometers with high gain and the use of high gain amplifiers can enable a good signal-to-noise ratio.

10 is a control circuit block diagram schematically showing the overall configuration of a charge amplifier according to an embodiment of the present invention. The gain control unit 300, the peak detection unit 400, and the transient input detection unit 500 can be roughly divided into the charge interface unit 100, the normalization unit 200, the gain control unit 300, The detailed function and configuration of each part are as follows.

11 is a specific circuit diagram of a charge amplifier according to an embodiment of the present invention. 12 is a circuit diagram specifically showing a charge interface portion of the charge amplifier. 11 and 12, the charge interface unit 100 firstly reduces the amplification of unwanted signals to the input signal, blocks the input of the DC component, supplies the constant voltage, And a comparator 110 for comparing the fine signal that has passed through the constant voltage supply and filtering unit 110 with the analog ground signal and comparing the difference to an analog inverse signal of the first OP-AMP (OP1) (OP1) and a second resistor (R2, R3) having different resistance values are connected to a non-inverting terminal of the first OP-AMP (OP1) and a second resistor A ground signal generation unit 130 connected to the inverting terminal and connected to the comparison switch 120 respectively, and a first OP-AMP (OP1) for amplifying the signal input to the non-inverting terminal and the inverting terminal, ), The magnitude of the input signal and the frequency In order to adjust the one end is connected to the output terminal of the first OP-AMP 1 (OP1), the other end is made up of an input signal level and the frequency control unit 140 connected to the positive voltage supply and filtering unit 110.

The comparison switch 120 is composed of a JFET and is composed of two switches. The input signal size and frequency controller 140 includes a switching terminal for inputting the output value as is (x1) to adjust the feedback resistance value and an A < th > switch SW1A and a first B switch SW1B are provided and a second switch SW2 for adjusting the frequency is connected to the first B switch SW1B.

A capacitor C5 and a resistor R8 are connected in series between the non-inverting terminal and the inverting terminal of the first OP-AMP OP1 in order to reduce signal interference of the input two signals. Further, low-pass filters R12, R13, C8, and C9 are further provided between the a-point task 1 OP-AMP (OP1) at which the signal output from the charge interface unit 100 is output.

In the charge interface unit 100 configured as described above, the input signal sensed from the piezoelectric element passes through the constant voltage supply and filtering unit 110 formed at the input terminal, and then passes through the two switching element JFETs to the first OP-AMP (OP1) And amplified. Here, the switching element JFET compares the fine signal coming through the sensor with the analog ground signal and inputs the fine difference to the first OP-AMP (OP1).

If the sensitivity of the sensor is in the range of 0.1 to 1 pC / g, the input option switch is fixed to x 1, while the input option switch is set to 1 To 10 pC / g, it is fixed at × 10 and used. In general, the frequency option switch is used at 1 Hz, but when the frequency response of 1 Hz or less is required, the switch is used at 0.1 Hz.

The fine signal coming from the sensor is amplified to a size enough to be processed by the connected system in the future. At this time, the filter not only reduces the amplification of unnecessary signals but also blocks the input of the DC component. In addition, two capacitors (C1, C2) are further connected to design a low pass filter (LPF) in a desired range by using C1 + C2 = 318 / Cutoff Frequency (㎑).

13 is a circuit diagram specifically showing a normalization unit of the charge amplifier. 11 and 13, the normalization unit 200 may include a second OP (not shown) in which a signal output from the point a is input to a non-inverting terminal and a inverting terminal is grounded to amplify a signal output from the point a, AMP (OP2) and the second OP-AMP (OP2) to output a unique value of 1 picoseconds for a value of 1 g and to set the sensitivity of the sensor itself, And a sensor sensitivity setting unit 210 including a feedback resistor module in which at least one module connecting a plurality of resistors is connected between the output terminal of the operational amplifier OP2 and the non-inverting terminal.

The signal received through the charge interface unit 100 sets the sensitivity of the sensor itself through the connection of various feedback resistors in the normalization unit. Thus, the value passed through the second OP-AMP (OP2) And changes to a signal which gives a unique value of 1 pF for one value, that is, 1 g. This value is output to the outside through the first output terminal (O / P1) or outputted to the point b. Since the feedback resistors used here are very sensitive through the second OP-AMP (OP2), a 1% precision resistor is used, and a sensitivity control switch consisting of three units in total has four resistors per unit And 12 kinds of resistance values are combined.

14 is a circuit diagram specifically showing a gain control section of the charge amplifier. 11 and 14, the gain adjuster 300 includes a first gain adjuster 310 and a second gain adjuster 320 that perform gain adjustment on the fixed signal output from the point b, . The first gain control unit 310 includes a first gain control switch (not shown) that can receive a fixed signal output from the point b and input and output a signal having a plurality of gain values between the non-inverting terminal and the output terminal And a third OP-AMP (OP3) provided with a capacitor C13 which is charged and discharged according to the selection of the first gain control switch 311. The first OP-

In addition, the second gain controller 320 receives the signal integrated from the third OP-AMP (OP3) at the inverting terminal and inputs / outputs a signal having a plurality of gain values between the non-inverting terminal and the output terminal And a fourth OP-AMP (OP4) which is provided with a gain control switch 321 and a capacitor C14 which is charged / discharged according to the selection of the second gain control switch 321. [

The fixed signal (1 ㎷ / g Fixed) passing through the normalization unit 200 is converted into a fixed signal (1 ㎷ / g Fixed) through a combination of two third OP-AMP (OP3) and fourth OP- (O / P2) and the point c are converted into signals having the gain values of the branches (100 psi / 0.3 g, 1 g, 3 g, 10 g, 30 g, and 100 g).

15 is a circuit diagram specifically showing a peak detecting portion of the charge amplifier. Referring to FIGS. 11 and 15, the peak detector 400 includes a non-inverting terminal to which a signal output from the point c is input, a non-inverting terminal to which the signal outputted from the point c is input, A fifth OP-AMP (OP5) having a diode (D6) for rectifying an AC component to a DC component, a non-inverting terminal to which the signal output from the fifth OP-AMP (OP5) A rectifying part 410 composed of a sixth OP-AMP (OP6) provided with a diode D8 for rectifying an AC component to a DC component, and a smoothing part 420 for smoothing the signal output from the rectifying part 410 .

In order to output the maximum value of the signal output through the gain controller 300, the AC component is changed to a DC component in the peak detector 400. In the fifth OP-AMP (OP5) in the LF422 chip, 6 OP-AMP (OP6) and four 1N4148 diodes (D6, D7, D8, D9). This signal, which has been converted to a DC component, has a maximum value through the DC output (BNC Connector, DC O / P) and point d.

16 is a circuit diagram specifically showing a transient input detecting section of the charge amplifier. Referring to FIGS. 11 and 16, the transient input detecting unit 500 detects whether the signal output from the point d is a non-inverting terminal, so that the signal output from the point d can be checked to be within a linear operating range of the meter. A seventh OP-AMP (OP7) to which a limit voltage is applied by the distribution resistors R44 and R45 to the inverting terminal and a non-inverting terminal of the seventh OP-AMP (OP7) And an LED 510 connected to an output terminal of the seventh OP-AMP (OP7).

And is used to be indicated through the LED 510 through an overload detection unit so that the maximum output signal output from the peak detector 400 can be operated within a linear operating range of the meter. TL061 chip is connected to the inverting terminal of the seventh OP-AMP (OP7) and the input signal is connected to the non-inverting terminal side. When the input signal exceeds the limit voltage, the current flows and the seventh OP - LED (510) connected to the AMP (OP7) output side lights up.

As described above, the electrostatic charge amplifier for an acceleration sensor according to the present invention extends the versatility of the charge-type charge amplifier by allowing the user to input and use the input range according to the capacitance of the accelerometer or according to the sensitivity of the accelerometer have.

In addition, since the detection section for the transient input is also provided at the output, it is possible to know whether the input value is excessively inputted from the output signal value.

In addition, it can be used to diagnose premature failure in large facilities such as power plants, steel mills, chemical plants, paper mills, and oil refineries in the main industry, research and development for vibration reduction required for product development in various companies including automobile companies, It can be used together with an electrostatic accelerometer for safety diagnosis of high-rise buildings including apartments.

On the other hand, considering the signal reduction and the noise generation on the line, it is possible to satisfy all the requirements such as whether the distance measurement is possible by using the electrostatic amplifier.

It should be apparent that the present invention is not limited to the above-described embodiment, and many modifications may be made by those skilled in the art without departing from the spirit of the present invention.

Claims (10)

A desired band is filtered with respect to the signal transmitted from the acceleration sensor, amplification is performed by outputting the difference between the filtered signal and the reference signal, and selective switching is performed to adjust the magnitude and frequency of the input signal A charge interface section; A feedback resistor module connecting a plurality of resistors to each unit is connected between the input and output terminals of at least one OP-AMP to set the sensor sensitivity by selective switching, and the signal conversion is performed by the unit voltage value with respect to the unit acceleration value part; A gain control unit for performing selective switching at one terminal of each of at least one OP-AMP continuously combined to output a corresponding voltage value corresponding to the acceleration value, and outputting a corresponding gain value; A peak detector for converting a DC component into a DC component by rectifying and smoothing to output a maximum DC value from a signal output from the gain controller; And Wherein a warning is issued at a value equal to or higher than a limit voltage value by comparing the maximum DC value with a limit voltage value to determine whether the maximum DC value output from the peak detector is within a measurement operation range, And an output terminal of the charge amplifier. 2. The charge pump circuit according to claim 1, A constant voltage supply and filtering unit for controlling a DC component when a signal outputted from the acceleration sensor is inputted and generating a constant voltage and passing a desired band signal; A ground signal generator for generating a reference signal which is an analog ground signal; A comparison switch for comparing the fine signal having passed through the constant voltage supply and filtering unit with a reference signal and outputting the difference; A first OP-AMP connected to a non-inverting terminal at one end of the comparing switch and having an inverting terminal connected to the other end of the comparing switch for performing signal amplification; And An input size selection switching unit for switching a feedback resistance value to adjust the size of an input signal transmitted from the acceleration sensor, and an input size selection switching unit selectively connected to the input size selection switching unit to adjust the frequency of the input signal The input signal size and frequency adjustment unit And an output terminal connected to the output terminal. 3. The apparatus of claim 2, wherein the input size selection switch comprises: (PC / g) to 10 (pC / g) when the sensitivity of the sensor connected to the output terminal of the first OP-AMP is between 0.1 (pC / g) and 1 A first switch SW1A which is selectively connected to a terminal to which the first switch SW1A is connected; And The terminal connected to the frequency selection switching unit distinguishes the case where the sensitivity of the sensor is between 0.1 (pC / g) and 1 (pC / g) and between 1 (pC / g) and 10 A first B switch (SW1B) And an output terminal connected to the output terminal. 3. The apparatus of claim 2, Is a second switch (SW2) which is selectively connected to a terminal that distinguishes between a case where the required frequency response is between 0.1 Hz and 1 Hz and a case when the frequency response is 1 Hz. The apparatus according to claim 1, A second OP-AMP connected such that the signal output from the first OP-AMP is input to the non-inverting terminal for amplifying the signal output from the charge interface and the inverting terminal is grounded; And A feedback resistor is connected between the output terminal and the non-inverting terminal of the second OP-AMP to set the sensitivity of the sensor, and at least one feedback resistor module connected with resistors having a plurality of different resistance values for each unit is connected A sensor sensitivity setting section in which selective switching is performed in each feedback resistance module And an output terminal connected to the output terminal. The charge amplifier according to claim 5, wherein the resistance value of the resistor forming the sensor sensitivity setting unit has an error value within a range of 0.1% to 1%. The apparatus of claim 1, A third gain control switch SW4A connected to the inverting terminal for outputting a fixed signal output from the normalizing section and capable of inputting / outputting a signal having a plurality of gain values between the non-inverting terminal and the output terminal, A first gain controller composed of OP-AMP; And A fourth OP-AMP connects the output terminal of the third OP-AMP to the inverting terminal and connects a second gain control switch (SW4B) capable of inputting and outputting a signal having a plurality of gain values between the non-inverting terminal and the output terminal The second gain adjustment unit And an output terminal connected to the output terminal. The apparatus of claim 1, wherein the peak detector comprises: A fifth OP-AMP connected between the inverting terminal and the output terminal so as to rectify the AC component to a DC component; A sixth OP-AMP having a non-inverting terminal connected to the rectifying diode at the output terminal of the fifth OP-AMP and having a diode rectifying an AC component to a DC component between the inverting terminal and the output terminal; And And a rectifying diode connected to the output terminal of the sixth OP-AMP for smoothing the rectified signal, And an output terminal connected to the output terminal. The apparatus of claim 1, wherein the transient input detector comprises: A comparator connected so that the signal output from the peak detecting unit can be input to the non-inverting terminal and the limiting voltage due to the dividing resistor is input to the inverting terminal to perform comparison; And a lighting unit connected to an output terminal of the comparator And an output terminal of the charge amplifier. The charge amplifier according to claim 9, wherein the lighting means is an LED.