Measuring circuit of frequency-band-selectable IEPE acceleration sensor

Abstract

The utility model discloses a frequency-band-selectable measurement circuit of an IEPE acceleration sensor, and the circuit comprises an upper computer which is provided with a man-machine interaction input window so as to receive the input of a preset frequency parameter through the input window; the signal conditioning circuit is used for conditioning the acceleration signal output by the IEPE acceleration sensor to obtain an initial conditioning signal; and the signal processing circuit is connected with the signal conditioning circuit and the upper computer and is used for receiving the initial conditioning signal and the preset frequency parameter and intercepting a target conditioning signal corresponding to the preset frequency parameter. According to the technical scheme provided by the invention, the acceleration value is measured in a specific frequency range, and the convenience of measuring the acceleration value in different frequency bands is also improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of circuit design, specifically related to a selectable band's IEPE acceleration sensor's measurement circuit. BACKGROUND

[0002] IEPE acceleration sensor is built-in an integrated circuit amplifier, can amplify weak piezoelectric signal and convert into low impedance output. IEPE acceleration sensor has high sensitivity, strong anti-interference ability, good reliability and other advantages, has been widely applied in the vibration measurement field. With the rapid development of environmental test equipment industry, the demand of environmental vibration test is increasing, and the measurement of acceleration becomes the key parameter of evaluating the effect of vibration test.

[0003] In order to accurately obtain the acceleration value in environmental vibration test, especially in the use of IEPE acceleration sensor, IEPE acceleration sensor and signal processing circuit need to be integrated together, in the design and application of IEPE signal processing circuit, the frequency of input signal is always considered, the frequency of input signal is related to the bandwidth of signal processing circuit, too narrow bandwidth will lead to the great reduction of input signal amplitude, it is difficult to determine whether the amplitude change of output signal is caused by bandwidth or signal processing circuit. At present, the processing of IEPE output signal is mainly completed through the second order hardware rectifier filter circuit composed of resistance and capacitance, and the size of current acceleration is determined by measuring the peak to peak value of voltage signal after filtering fixed high frequency component.

[0004] However, the method of fixed filtering frequency can only understand the response characteristics of the sensor in a large frequency range, and it is not easy to observe the response characteristics in a specific frequency range. Such function requirements are not consistent with the current high acceleration stress screening test, mainly reflected in the different starting frequency and cutoff frequency of output signal, so the measurement method of fixed cutoff frequency filtering is difficult to meet the test requirements.

[0005] There is a kind of high-precision measurement circuit of IEPE acceleration sensor at present, under the condition of considering high-frequency noise interference, the acceleration sensor is processed and filtered through low-noise preamplifier, the direct current bias is filtered out through capacitance, only the alternating current signal component is reserved, then the cutoff frequency of filter is set through RC low pass filter circuit, so that the signal below the frequency is allowed to pass through, and the signal above the frequency is attenuated, and then the operational amplifier follower is used for buffering and isolating the front and rear circuits to prevent the mutual influence between the front and rear circuits. The circuit successfully realizes the accurate measurement of IEPE acceleration sensor. In the test process, the resistance, capacitance and the like in the circuit are fixed values, and the measurement of acceleration value in a specific frequency range still cannot be realized.

[0006] Therefore, there is an urgent need for a circuit capable of measuring acceleration values in a specific frequency range. Utility model content

[0007] The utility model discloses a kind of selectable band IEPE acceleration sensor's measurement circuit, to be able to realize the measurement of IEPE acceleration sensor in specific frequency band.

[0008] To achieve the above object, the utility model provides a kind of selectable band IEPE acceleration sensor's measurement circuit, comprising:

[0009] Host computer has the input window of man-machine interaction to receive the input of preset frequency parameter by input window;

[0010] Signal conditioning circuit is used to condition acceleration signal output by IEPE acceleration sensor, and obtain initial conditioning signal;

[0011] Signal processing circuit is connected with signal conditioning circuit and host computer, for receiving initial conditioning signal and preset frequency parameter, and intercepting target conditioning signal corresponding to preset frequency parameter.

[0012] In another embodiment, signal processing circuit includes signal sampling module, frequency band selection module and DAC module;

[0013] Signal sampling module is used to sample resolution to initial conditioning signal, and obtain sampling signal;

[0014] Frequency band selection module is used to select sampling signal according to preset frequency parameter, and obtain preset frequency signal;

[0015] DAC module is used for analog-digital conversion processing to preset frequency signal, and obtains and outputs target conditioning signal.

[0016] In another embodiment, frequency band selection module includes low-pass filter and band-pass filter;

[0017] Low-pass filter and band-pass filter are used to select preset frequency signal from sampling signal;

[0018] Low-pass filter and band-pass filter low-pass filter cutoff frequency, band-pass filter cutoff frequency and output sensitivity are set according to preset frequency parameter.

[0019] In another embodiment, the model of main control chip of signal processing circuit is STM32F407VET6.

[0020] In another embodiment, signal conditioning circuit includes signal filtering module, reference voltage lifting module, positive amplification module;

[0021] The signal filtering module is used for filtering out the DC component in the acceleration signal to obtain an alternating conditioning signal.

[0022] The reference voltage lifting module is used for lifting the reference voltage of the alternating conditioning signal to obtain a lifted conditioning signal.

[0023] The positive amplification module is used for amplifying the lifted conditioning signal to obtain an initial conditioning signal.

[0024] In another embodiment, the signal filtering module comprises a capacitor for removing the DC component in the acceleration signal.

[0025] In another embodiment, the measurement circuit of the IEPE acceleration sensor of the optional frequency band further comprises:

[0026] The power supply circuit is connected with the IEPE acceleration sensor, the signal conditioning circuit and the signal processing circuit, and is used for supplying power to the IEPE acceleration sensor, the signal conditioning circuit and the signal processing circuit.

[0027] In another embodiment, the power supply circuit comprises a voltage conversion module and a voltage filtering module.

[0028] The voltage conversion module is used for receiving an input current and adjusting the voltage of the input current to obtain a transition current.

[0029] The voltage filtering module is used for filtering out the common-mode interference signal in the transition current to obtain an output current.

[0030] In another embodiment, an excitation constant current source is further arranged between the power supply circuit and the IEPE acceleration sensor.

[0031] The excitation constant current source is used for adjusting the power supply state of the power supply circuit to the IEPE acceleration sensor.

[0032] In another embodiment, the measurement circuit of the IEPE acceleration sensor of the optional frequency band further comprises:

[0033] The output circuit is connected with the signal processing circuit, and the output circuit is used for adjusting the amplitude of the target conditioning signal and outputting the target conditioning signal.

[0034] The utility model discloses the beneficial effect lies in:

[0035] The measurement circuit in the utility model can realize the input of preset frequency parameters through the man-machine interaction window of the upper computer, so that the signal processing circuit can intercept the target conditioning signal corresponding to the preset frequency parameters in the initial conditioning signal according to the preset frequency parameters, that is, when the IEPE acceleration sensor of a specific frequency band needs to be measured, only the specific frequency needs to be input into the upper computer through the input window of man-machine interaction, the acceleration value measurement in the specific frequency range is realized, and the convenience of measuring the acceleration value in different frequency bands is also increased.

[0036] The above description is only a summary of the technical scheme of the utility model, in order to more clearly understand the technical means of the utility model, and can be implemented according to the content of the specification, the following preferred embodiments of the utility model are described in detail with the help of the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 The structure diagram of the measurement circuit of the IEPE acceleration sensor of the optional frequency band shown in an embodiment of the application;

[0038] Figure 2 The processing flow chart of the signal processing circuit shown in an embodiment of the application;

[0039] Figure 3 The interface schematic diagram of the upper computer man-machine interaction input window shown in an embodiment of the application;

[0040] Figure 4 The circuit structure diagram of the signal conditioning circuit shown in an embodiment of the application;

[0041] Figure 5 The circuit structure diagram of the power supply circuit shown in an embodiment of the application;

[0042] Figure 6 The circuit structure diagram of the excitation constant current source shown in an embodiment of the application;

[0043] Figure 7 The circuit structure diagram of the output circuit shown in an embodiment of the application;

[0044] Figure 8 The circuit structure diagram of another output circuit shown in an embodiment of the application;

[0045] Figure 9 The structure diagram of the measurement circuit of the IEPE acceleration sensor of the optional frequency band shown in an embodiment of the application. DETAILED DESCRIPTION

[0046] The technical solutions of the utility model will be described clearly and completely in connection with the drawings below, obviously, the described embodiments are part of the embodiments of the utility model, rather than all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by the ordinary skilled in the art without making creative labor belong to the protection scope of the utility model.

[0047] It needs to be explained that the description of "one embodiment", "embodiment", "example embodiment" and the like in the specification means that the described embodiment can include specific features, structures or characteristics, but not every embodiment must include these specific features, structures or characteristics. In addition, such expressions do not mean the same embodiment. Further, when a specific feature, structure or characteristic is described in connection with an embodiment, it is shown that such feature, structure or characteristic is combined into other embodiments within the knowledge of the skilled in the art, whether or not it is explicitly described.

[0048] In addition, some words are used in the specification and subsequent claims to refer to specific components or parts, and those with ordinary knowledge in the art should understand that manufacturers can use different names or terms to refer to the same component or part. The specification and subsequent claims do not distinguish components or parts by name, but by the functional difference between components or parts. In the entire specification and subsequent claims, "including" and "containing" are open terms, so they should be interpreted as "including but not limited to". In addition, the word "connected" here includes any direct and indirect electrical connection means. Indirect electrical connection means includes connection through other devices.

[0049] Please see Figure 1 The structure diagram of the measurement circuit of the alternative frequency band IEPE acceleration sensor shown in a preferred embodiment of the application comprises: an upper computer, which has an input window for human-computer interaction to receive the input of the preset frequency parameter through the input window; a signal conditioning circuit, which is used for conditioning the acceleration signal output by the IEPE acceleration sensor to obtain an initial conditioning signal; a signal processing circuit, which is connected with the signal conditioning circuit and the upper computer, and is used for receiving the initial conditioning signal and the preset frequency parameter, and intercepting a target conditioning signal corresponding to the preset frequency parameter.

[0050] Optionally, the host computer can be a computer device, and an operator can input the preset frequency parameter into the host computer through an input window of human-computer interaction of the host computer. The host computer sends the preset frequency parameter as an instruction to the signal processing circuit. The signal conditioning circuit first conditions the acceleration signal output by the IEPE acceleration sensor to condition the acceleration signal into an initial conditioning signal suitable for the signal processing circuit. However, the frequency range of the initial conditioning signal at this time is high, and not all frequency bands of the initial conditioning signal are needed. Therefore, after the signal processing circuit receives the initial conditioning signal, the signal processing circuit can intercept a target conditioning signal corresponding to the preset frequency parameter from the initial conditioning signal according to the instruction containing the preset frequency parameter sent by the host computer, that is, select the intersection part of the initial conditioning signal with the preset frequency parameter.

[0051] The optional frequency band IEPE acceleration sensor measurement circuit in the above embodiment can input the preset frequency parameter through the human-computer interaction window of the host computer, so that the signal processing circuit can intercept the target conditioning signal corresponding to the preset frequency parameter from the initial conditioning signal according to the preset frequency parameter. That is, when the IEPE acceleration sensor of a specific frequency band needs to be measured, only the specific frequency needs to be input into the host computer through the input window of human-computer interaction, so as to realize acceleration value measurement in a specific frequency range and increase the convenience of acceleration value measurement in different frequency bands.

[0052] Referring to Figure 2 , Figure 2 A signal processing circuit processing flowchart, the signal processing circuit includes a signal sampling module, a frequency band selection module and a DAC module; the signal sampling module is used for resolution sampling of the initial conditioning signal to obtain a sampling signal; the frequency band selection module is used for selecting the sampling signal according to the preset frequency parameter to obtain a preset frequency signal; the DAC module is used for analog-digital conversion processing of the preset frequency signal to obtain and output a target conditioning signal. The frequency band selection module includes a low-pass filter and a band-pass filter; the low-pass filter and the band-pass filter are used for selecting the preset frequency signal from the sampling signal; the low-pass filter cutoff frequency, the band-pass filter cutoff frequency and the output sensitivity of the low-pass filter and the band-pass filter are set according to the preset frequency parameter.

[0053] Exemplarily, the model of the main control chip of the signal processing circuit is STM32F407VET6, the signal sampling module can adopt an external 16-bit ADC chip AD7606, the target conditioning signal is sampled by using a sampling frequency of 256KHz to obtain a sampling signal, the sampling signal is input into the STM32 chip of the frequency band selection module, the sampling signal is subjected to fast Fourier transform, and then a low-pass filter and a band-pass filter are designed by using a window function method to select a preset frequency signal from the sampling signal, wherein the low-pass filter can be a fourth-order Butterworth low-pass filter, and the band-pass filter can be a fourth-order Butterworth band-pass filter. The host computer inputs an IP address, a port and a slave address to realize connection with the signal processing circuit (see Figure 3 , Figure 3 for an interface schematic diagram of an upper computer human-computer interaction input window), and then inputs a preset frequency parameter from the human-computer interaction input window, sends data to the STM32 after the input is completed, and then outputs the data by a 16-bit DAC chip DAC2167 chip to realize output of a target conditioning signal (DAC_OUT2) corresponding to the preset frequency parameter. Finally, the mean square value of the target conditioning signal in the frequency domain corresponding to the preset frequency parameter is calculated, and the effective value of the acceleration signal in a specific frequency band can be output.

[0054] The signal processing circuit in the above embodiment can output the effective value of the acceleration signal in a specific frequency band, that is, the problems in the prior art are overcome, the acceleration value measurement in a specific frequency range is realized, and the convenience of measuring the acceleration value in different frequency bands is also increased.

[0055] Referring to Figure 4 , Figure 4 for a circuit structure diagram of a signal conditioning circuit, the signal conditioning circuit comprises a signal filtering module, a reference voltage lifting module and a positive amplification module; the signal filtering module is used for filtering out a direct current component in an acceleration signal to obtain an alternating conditioning signal; the reference voltage lifting module is used for lifting the reference voltage of the alternating conditioning signal to obtain a lifted conditioning signal; and the positive amplification module is used for amplifying the lifted conditioning signal to obtain an initial conditioning signal. The signal filtering module comprises a capacitor, and the capacitor is used for removing the direct current component in the acceleration signal.

[0056] Optionally, a low-noise preamplifier can be used in the signal filtering module to process and filter the signals of the acceleration sensor, which can effectively suppress noise and interference. Since the IEPE acceleration sensor outputs an acceleration signal as an AC signal with a DC bias, the capacitor C94 in the signal filtering module can filter out the DC bias and only retain the AC signal component, obtaining an AC conditioning signal. Then, the reference voltage lifting module can use a DC lifting method to lift the reference voltage of the AC conditioning signal, for example, lifting the reference voltage of the AC conditioning signal to 1.25V, obtaining a lifted conditioning signal. The op-amp follower in the positive amplification module is used to buffer and isolate the front and rear circuits to prevent mutual influence between them. The DC gain of the op-amp follower can be designed as 0dB, which further amplifies the lifted conditioning signal, for example, amplifying the lifted conditioning signal by two times to obtain an initial conditioning signal (IEPE_2.5).

[0057] The signal conditioning circuit in the above embodiment can realize the conditioning of the acceleration signal into an initial conditioning signal suitable for the signal processing circuit, facilitating the processing of the initial conditioning signal by the subsequent signal processing circuit.

[0058] In another embodiment, the measurement circuit of the IEPE acceleration sensor of the optional frequency band further includes a power supply circuit, as shown in Figure 5 , Figure 5 is a circuit structure diagram of a power supply circuit. The power supply circuit is connected with the IEPE acceleration sensor, the signal conditioning circuit and the signal processing circuit, and is used to supply power to the IEPE acceleration sensor, the signal conditioning circuit and the signal processing circuit. The power supply circuit includes a voltage conversion module and a voltage filtering module. The voltage conversion module is used to receive an input current and adjust the voltage of the input current to obtain a transition current. The voltage filtering module is used to filter out common-mode interference signals in the transition current to obtain an output current.

[0059] For example, the voltage conversion module of the power supply circuit takes the external DC 24V power supply as the input signal DC_IN. The SS56 Schottky rectifier diode D1 is used to suppress the inrush current. The 10uF capacitor C39 is used to filter out high-frequency noise in the power supply. Then, the DC 24V voltage is input from the VIN pin of the TPS5430DDA. At this time, the VSNS pin outputs a reference DC voltage of 1.221V. The voltage dividing circuit composed of the potentiometer R14 and the fixed resistor R22 adjusts the potentiometer R14, and according to formula (1), the DC_OUT+ output is 12V.

[0060]

[0061] DC_OUT- and DC_OUT+ have the same principle. According to formula (2), DC_OUT- outputs -12V. Similarly, the voltage dividing circuit composed of R26 and R29 outputs 5V.

[0062]

[0063] That is, the voltage adjustment of the input current is completed to obtain the transition current; then a filter capacitor is placed in the front stage of the voltage filter module for filtering, which can effectively suppress the common-mode interference signal, ensure that the entire circuit obtains a stable power supply, and finally obtain the output current to power the signal conditioning circuit and signal processing circuit.

[0064] The power supply circuit in the above embodiment realizes stable power supply to the signal conditioning circuit and the signal processing circuit, thereby improving the stability of the entire measurement circuit.

[0065] In another embodiment, the IEPE acceleration sensor cannot be powered directly by the power supply circuit, but must be powered by a constant current excitation circuit, otherwise the sensor may be easily burned out. Figure 6 , Figure 6 This is a circuit structure diagram of an excitation constant current source. An excitation constant current source is also provided between the power supply circuit and the IEPE acceleration sensor. The excitation constant current source is used to adjust the power supply state of the power supply circuit to the IEPE acceleration sensor.

[0066] Optionally, the excitation constant current source can stably output a current of 4 to 20 mA to power the IEPE accelerometer. The excitation constant current source adopts the field effect transistor U10, and utilizes the relationship between its gate-source voltage and drain current and the resistors U20, U9, and R3 to achieve a constant current adjustable output. The output signal is I_OUT. When the gate voltage is low, the constant current output is turned off, that is, the excitation constant current source ensures that the current input to the IEPE accelerometer is a stable current, thereby protecting the IEPE accelerometer and avoiding the IEPE accelerometer from burning due to unstable current.

[0067] In another embodiment, after the signal processing circuit outputs the target conditioned signal, in order to facilitate subsequent processing of the target conditioned signal, it is also necessary to use an output circuit to output the target conditioned signal. Therefore, the measurement circuit of the IEPE acceleration sensor of the selected frequency band also includes an output circuit. Figure 7 and Figure 8 , Figure 7 and Figure 8 The output circuit is connected to the signal processing circuit and is used to adjust the amplitude of the target conditioned signal and output it.

[0068] For example, the subsequent external device usually needs a 0-10V signal when processing the signal, but the target conditioning signal is usually 2.5V, in order to facilitate the secondary processing of the target conditioning signal by the subsequent external device, the output circuit needs to adjust the amplitude of the target conditioning signal, and usually needs to adjust the amplitude of the target conditioning signal to 0-10V.

[0069] In order to more clearly illustrate the connection relationship between various circuits, as shown in Figure 9 Figure 9 Another alternative frequency band IEPE acceleration sensor measurement circuit structure diagram of a preferred embodiment is shown.

[0070] The technical features of the above embodiments can be combined in any way, in order to make the description concise, not all possible combinations of the technical features in the above embodiments are described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the description.

[0071] The above embodiments only express several implementation manners of the utility model, the description is more specific and detailed, but it cannot be understood as the limitation of the scope of the utility model patent. It should be pointed out that for ordinary skilled in the art, on the premise of not departing from the concept of the utility model, a number of modifications and improvements can be made, which belong to the protection scope of the utility model. Therefore, the protection scope of the utility model patent should be subject to the appended claims.​

Claims

1. A measurement circuit for an IEPE acceleration sensor with a selectable frequency band, characterized in that: include: A host computer having an input window for human-computer interaction to receive input of preset frequency parameters through the input window; A signal conditioning circuit is used to condition the acceleration signal output by the IEPE acceleration sensor to obtain an initial conditioning signal; The signal processing circuit is connected to the signal conditioning circuit and the host computer, and is used to receive the initial conditioning signal and the preset frequency parameter, and intercept the target conditioning signal corresponding to the preset frequency parameter.

2. The circuit according to claim 1, wherein The signal processing circuit includes a signal sampling module, a frequency band selection module and a DAC module; The signal sampling module is used to perform resolution sampling on the initial conditioned signal to obtain a sampled signal; The frequency band selection module is used to select the sampling signal according to the preset frequency parameter to obtain a preset frequency signal; The DAC module is used to perform analog-to-digital conversion on the preset frequency signal to obtain and output the target conditioned signal.

3. The circuit according to claim 2, wherein: The frequency band selection module includes a low-pass filter and a band-pass filter; The low-pass filter and the band-pass filter are used to select the preset frequency signal from the sampling signal; The low-pass filter cutoff frequency, the band-pass filter cutoff frequency and the output sensitivity of the low-pass filter and the band-pass filter are set according to the preset frequency parameters.

4. The circuit according to claim 2, wherein: The model of the main control chip of the signal processing circuit is STM32F407VET6.

5. The circuit according to claim 1, wherein The signal conditioning circuit includes a signal filtering module, a reference voltage raising module, and a forward amplification module; The signal filtering module is used to filter out the DC component in the acceleration signal to obtain an AC conditioning signal; The reference voltage raising module is used to raise the reference voltage of the AC conditioning signal to obtain a raised conditioning signal; The forward amplification module is used to amplify the lifting conditioned signal to obtain the initial conditioned signal.

6. The circuit according to claim 5, wherein: The signal filtering module includes a capacitor, which is used to remove the DC component in the acceleration signal.

7. The circuit according to claim 1, wherein: Also includes: The power supply circuit is connected to the IEPE acceleration sensor, the signal conditioning circuit and the signal processing circuit, and is used to supply power to the IEPE acceleration sensor, the signal conditioning circuit and the signal processing circuit.

8. The circuit according to claim 7, wherein: The power supply circuit includes a voltage conversion module and a voltage filtering module; The voltage conversion module is used to receive an input current and adjust the voltage of the input current to obtain a transition current; The voltage filtering module is used to filter out the common-mode interference signal in the transition current to obtain the output current.

9. The circuit according to claim 7, wherein: An excitation constant current source is also provided between the power supply circuit and the IEPE acceleration sensor; The excitation constant current source is used to adjust the power supply state of the power supply circuit to the IEPE acceleration sensor.

10. The circuit according to claim 1, wherein Also includes: An output circuit is connected to the signal processing circuit, and is used to adjust the amplitude of the target conditioned signal and output it.

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