Flowmeter filter circuit

Abstract

The utility model belongs to the technical field of flow meters, and provides a flow meter filter circuit which comprises a charge amplifier, a program control second-order low-pass filter and a first-order high-pass filter which are sequentially connected, the input end of the charge amplifier is connected with a sensor, and the output end of the charge amplifier is connected with the program control second-order low-pass filter. The first-order high-pass filter and the program-controlled second-order low-pass filter both comprise digital potentiometers, and the filtering frequency band is adjusted by adjusting the digital potentiometers. According to the utility model, the flexible adjustment of the filtering band is realized by adjusting the digital potentiometer, and the flexible multi-point setting of the signal filtering band of the flowmeter is realized; meanwhile, by adjusting capacitors with different capacitance values connected with the charge amplifier, the signal amplification factor of the sensor can be dynamically adjusted.

Description

Technical Field

[0001] The utility model relates to the technical field of flow meters, and particularly relates to a flow meter filtering circuit. Background Art

[0002] When a fluid flows through a vortex street body, vortices are generated in the fluid. The vortices generate an upward lift force. The detection element acts on the piezoelectric crystal element with the received lift force in the form of stress and converts it into an alternating charge signal. After charge amplification, filtering, and shaping, a vortex frequency signal is obtained.

[0003] In practical applications, the sensor signal collected by the piezoelectric crystal is very small, and the sensor signal needs to be processed. Currently, a DIP switch group is used to set the filtering band of the filtering circuit during filtering processing. Although different gear selections of the DIP switch group can realize the adjustment of the filtering band of the filtering circuit, the amplification factor is limited by the number of gears switched by the DIP switch, and flexible adjustment cannot be achieved. Summary of the Utility Model

[0004] Aiming at the defects in the prior art, the utility model provides a flow meter filtering circuit to solve the problem that the current flow meter is limited by the DIP switch to adjust the filtering band of the filtering circuit and the amplification factor of the signal amplification circuit, and flexible adjustment cannot be achieved.

[0005] A flow meter filtering circuit provided by the utility model includes a charge amplifier, a programmable second-order low-pass filter, and a first-order high-pass filter connected in sequence.

[0006] The input end of the charge amplifier is connected to a sensor, the output end of the charge amplifier is connected to the programmable second-order low-pass filter, and both the first-order high-pass filter and the programmable second-order low-pass filter include digital potentiometers. The filtering frequency band is adjusted by adjusting the digital potentiometers.

[0007] It can be seen from the above technical solutions that the flow meter filtering circuit provided by the utility model realizes flexible adjustment of the filtering band by adjusting the digital potentiometers, and realizes flexible multi-point setting of the signal filtering frequency band of the flow meter.

[0008] Optionally, the programmable second-order low-pass filter includes a first digital potentiometer, a second digital potentiometer, and a first amplifier connected in series. The first digital potentiometer and the second digital potentiometer are connected in series with each other and connected to the positive input end of the first amplifier.

[0009] It further includes a first capacitor, a second capacitor and a third capacitor. One end of the first capacitor is connected to the negative input terminal of the first amplifier, and the other end of the first capacitor is connected between the first digital potentiometer and the second digital potentiometer. The second capacitor is connected between the second digital potentiometer and the negative input terminal of the first amplifier. The third capacitor is connected to the output terminal of the first amplifier.

[0010] Optionally, the first-order high-pass filter includes a second amplifier, a third digital potentiometer and a fourth digital potentiometer. The third digital potentiometer and the fourth digital potentiometer are respectively connected to the positive input terminal and the negative input terminal of the second amplifier. The positive input terminal of the second amplifier is connected to the output terminal of the programmable second-order low-pass filter.

[0011] Optionally, it further includes a first analog switch and a second analog switch.

[0012] The first analog switch controls, according to the CPU signal, the fourth capacitor and the first resistor to be connected to both ends of the first capacitor.

[0013] The second analog switch controls, according to the CPU signal, one end of the fifth capacitor to be connected between the second digital potentiometer and the positive input terminal of the first amplifier, and the other end of the fifth capacitor is grounded.

[0014] Optionally, the programmable second-order low-pass filter further includes a third analog switch and a sixth capacitor.

[0015] The third analog switch controls, according to the CPU signal, the sixth capacitor to be connected to both ends of the third capacitor.

[0016] Optionally, the charge amplifier includes a third amplifier, and a plurality of adjustment capacitors with different capacitance values are connected to the negative input terminal of the third amplifier.

[0017] It further includes a second resistor and a third resistor. One end of the second resistor is connected to the output terminal of the third amplifier, and the other end of the second resistor is connected to one of the adjustment capacitors. One end of the third resistor is grounded, and the other end of the third resistor is connected to the positive input terminal of the third amplifier.

[0018] Adopting the above technical solution, the present application has the following technical effects:

[0019] The flowmeter filtering circuit provided by the present utility model realizes flexible adjustment of the filtering band by adjusting the digital potentiometer, and realizes flexible multi-point setting of the signal filtering frequency band of the flowmeter.

[0020] The charge amplifier of the present utility model adjusts the dynamic adjustment of the amplification factor of the flowmeter for the acquired sensor signal by adjusting the capacitance value of the adjustment capacitor connected to the positive input terminal of the third amplifier. Description of the Drawings

[0021] In order to more clearly illustrate the specific embodiments of the present utility model or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. In all the drawings, similar elements or parts are generally denoted by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0022] Figure 1 It is a schematic diagram of a flowmeter filtering circuit provided by an embodiment of the present utility model;

[0023] Figure 2 It is Figure 1 a schematic diagram of the programmed second-order low-pass filter shown;

[0024] Figure 3 It is Figure 1 a schematic diagram of the first-order high-pass filter shown;

[0025] Figure 4 It is Figure 1 a schematic diagram of the charge amplifier shown. Detailed Embodiments

[0026] The following will describe in detail the embodiments of the technical solutions of the present utility model in conjunction with the drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present utility model, and thus are only examples and cannot be used to limit the protection scope of the present utility model.

[0027] It should be noted that unless otherwise specified, the technical terms or scientific terms used in this application should have the ordinary meaning understood by those skilled in the art to which the present utility model belongs.

[0028] In the description of this application, it should be understood that the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. In the description of the present utility model, "a plurality" means two or more unless otherwise specifically defined.

[0029] As Figure 1As shown in the figure, a flowmeter filtering circuit provided in this embodiment includes a charge amplifier, a programmable second-order low-pass filter, and a first-order high-pass filter connected in sequence. The input end of the charge amplifier is connected to a sensor, the output end of the charge amplifier is connected to the programmable second-order low-pass filter, and both the first-order high-pass filter and the programmable second-order low-pass filter include digital potentiometers. The filtering frequency band is adjusted by adjusting the digital potentiometers. Based on this, the flexible adjustment of the filtering band is realized by adjusting the digital potentiometers, and the flexible setting of the signal filtering frequency band of the flowmeter is achieved.

[0030] As Figure 2 shown, the programmable second-order low-pass filter includes a first digital potentiometer RP1, a second digital potentiometer RP2, and a first amplifier U1 connected in series. The first digital potentiometer RP1 and the second digital potentiometer RP2 are connected in series with each other and connected to the positive input end of the first amplifier U1; it also includes a first capacitor C1, a second capacitor C2, and a third capacitor C3. One end of the first capacitor C1 is connected to the negative input end of the first amplifier U1, the other end of the first capacitor C1 is connected between the first digital potentiometer RP1 and the second digital potentiometer RP2, the second capacitor C2 is connected between the second digital potentiometer RP2 and the negative input end of the first amplifier U1, and the third capacitor C3 is connected to the output end of the first amplifier U1.

[0031] As Figure 3 shown, the first-order high-pass filter includes a second amplifier U2, a third digital potentiometer RP3, and a fourth digital potentiometer RP4. The third digital potentiometer RP3 and the fourth digital potentiometer RP4 are respectively connected to the positive input end and the negative input end of the second amplifier U2, and the positive input end of the second amplifier U2 is connected to the output end of the programmable second-order low-pass filter.

[0032] Optionally, it further includes a first analog switch K1 and a second analog switch K2. The first analog switch K1 controls the fourth capacitor C4 and the first resistor R1 to be connected to both ends of the first capacitor C1 according to the CPU signal; the second analog switch K2 controls one end of the fifth capacitor C5 to be connected between the second digital potentiometer RP2 and the positive input end of the first amplifier U1 according to the CPU signal, and the other end of the fifth capacitor C5 is grounded.

[0033] Optionally, the programmable second-order low-pass filter further includes a third analog switch K3 and a sixth capacitor C6. The third analog switch K3 controls the sixth capacitor C6 to be connected to both ends of the third capacitor C3 according to the CPU signal.

[0034] The models of the first analog switch K1, the second analog switch K2, and the third analog switch K3 can be NLAS4157DFT2G(AN).

[0035] As Figure 4As shown, the charge amplifier includes a third amplifier U3. A number of adjusting capacitors C7 - C9 with different capacitance values are connected to the positive input terminal of the third amplifier U3. It also includes a second resistor R2 and a third resistor R3. One end of the second resistor R2 is connected to the output terminal of the third amplifier U3, and the other end of the second resistor R2 is connected to one of the adjusting capacitors C7 - C9. Different capacitance values of the capacitors achieve different amplification factors. One end of the third resistor R3 is grounded, and the other end of the third resistor R3 is connected to the positive input terminal of the third amplifier U3. Based on this, the charge amplifier adjusts the capacitance value of the capacitor connected to the negative input terminal of the third amplifier U3 to adjust the adjustment of the sensor signal obtained by the flowmeter.

[0036] In the description of the present utility model, a large number of specific details are set forth. However, it can be understood that the embodiments of the present utility model may be practiced without these specific details. In some instances, well-known methods, structures, and technologies are not shown in detail so as not to obscure the understanding of this description.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present utility model and are not intended to limit them. Although the present utility model has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features. These modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present utility model, and they should all be covered by the scope of the claims and the description of the present utility model.

Claims

1. A flow meter filter circuit, characterized in that: It includes a charge amplifier, a programmable second-order low-pass filter and a first-order high-pass filter connected in sequence. The input end of the charge amplifier is connected to the sensor, the output end of the charge amplifier is connected to the programmable second-order low-pass filter, and the first-order high-pass filter and the programmable second-order low-pass filter both include digital potentiometers, and the filter frequency band is adjusted by adjusting the digital potentiometers.

2. The flow meter filter circuit according to claim 1, characterized in that: The program-controlled second-order low-pass filter comprises a first digital potentiometer, a second digital potentiometer and a first amplifier connected in series, wherein the first digital potentiometer and the second digital potentiometer are connected in series with each other and connected to the positive input terminal of the first amplifier; It also includes a first capacitor, a second capacitor and a third capacitor, one end of the first capacitor is connected to the negative input end of the first amplifier, the other end of the first capacitor is connected between the first digital potentiometer and the second digital potentiometer, the second capacitor is connected between the second digital potentiometer and the negative input end of the first amplifier, and the third capacitor is connected to the output end of the first amplifier.

3. The flow meter filter circuit according to claim 2, characterized in that: The first-order high-pass filter includes a second amplifier, a third digital potentiometer and a fourth digital potentiometer. The third digital potentiometer and the fourth digital potentiometer are respectively connected to the positive input terminal and the negative input terminal of the second amplifier. The positive input terminal of the second amplifier is connected to the output terminal of the programmable second-order low-pass filter.

4. The flow meter filter circuit according to claim 3, characterized in that: Also includes a first analog switch and a second analog switch, The first analog switch controls the fourth capacitor and the first resistor to be connected to two ends of the first capacitor according to the CPU signal; The second analog switch controls one end of the fifth capacitor to be connected between the second digital potentiometer and the positive input end of the first amplifier according to the CPU signal, and the other end of the fifth capacitor is grounded.

5. The flow meter filter circuit according to claim 4, characterized in that: The programmable second-order low-pass filter also includes a third analog switch and a sixth capacitor. The third analog switch controls the sixth capacitor to be connected to two ends of the third capacitor according to a CPU signal.

6. The flow meter filter circuit according to claim 1, characterized in that: The charge amplifier comprises a third amplifier, a negative input terminal of the third amplifier is connected to a plurality of adjustment capacitors with different capacitances; It also includes a second resistor and a third resistor, one end of the second resistor is connected to the output end of the third amplifier, and the other end of the second resistor is connected to one of the adjustment capacitors; one end of the third resistor is grounded, and the other end of the third resistor is connected to the positive input end of the third amplifier.

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