TWI473977B - Automatically adjust the frequency threshold and the detection point of the tuning fork type sensing device - Google Patents

Description

Tuning fork sensing device for automatically adjusting frequency threshold and detection point

The invention relates to a tuning fork type sensing device, in particular to a tuning fork type sensing device and method capable of automatically adjusting a feedback frequency threshold and a sensing point according to changes in material properties.

The existing tuning fork type liquid level switch (tuning fork type sensing device) is mainly used for the measurement of the liquid level measurement of the chemical barrel tank, the food industry, the petrochemical industry, etc., in use, by driving a piezoelectric element to make a tuning fork The resonance frequency is generated. When the tuning fork touches the material, the tuning fork returns a frequency signal, and the material depth is judged by calculating the change of the frequency. However, as shown in FIG. 7, the signals reflected by the materials with different specific gravity are different. When measuring different specific gravity materials, there will be different inductive frequency changes in the tuning fork resonance groove. In order to ensure that the materials corresponding to different specific gravity can be correctly sensed in the tuning fork resonant groove, water with specific gravity of 1 is generally used as the basic reference point. The action threshold adjusting unit can adjust the action threshold frequency value when measuring different materials to achieve that the Sensing Point can maintain the position of the same tuning fork resonant groove sensing point.

When the material specific gravity is equal to a standard specific gravity (usually water), the sensing point position on the tuning fork 70 is equal to the standard sensing position S0, and when the material specific gravity is greater than the standard specific gravity, the sensing point position S1 on the tuning fork 70 will be lower than the The standard sensing position S0, when the material specific gravity is less than the standard specific gravity, the sensing point position S2 on the tuning fork 70 will be higher than the standard sensing position S0, so it must be manually re-matched with the different proportions of the materials contained in the tank. The Frequency Threshold is adjusted to ensure that a switching signal is fed back when the liquid level reaches the same standard sensing position. Known techniques have shown that their convenience is insufficient, and measurement accuracy and output stability are low, so there is a need for further improvement: US Patent Publication No. US2006/0053863A1 discloses how to use diagnostic methods to determine the oscillation portion suitable as a drive. In addition to the diagnosis of the oscillating part, this design method does not take into account the effects of different material specific gravity, which may make it difficult to lose the accuracy of the sensing point when the materials in the tank are different.

In view of the foregoing problems, the main object of the present invention is to provide a tuning fork type sensing device and method for automatically adjusting a frequency threshold and a detection point, which mainly performs self-adjusting action on the judgment of the sensing point, and continuously updates the tuning fork. The signal is used to discriminate the specific gravity of the material, so that the position of the sensing point does not change due to different materials, thereby maintaining the accuracy of the measurement and improving the output stability.

The main technical means for achieving the foregoing objective is that the tuning fork sensing device for automatically adjusting the frequency threshold and the offset adjusting sensing point comprises a tuning fork body and a signal processing module; wherein the signal processing module comprises a piezoelectric element is in contact with the tuning fork body; a signal processing circuit is mainly composed of a filter and an amplifier, and the filter receives the sensing signal sent from the piezoelectric element and sends it to the amplifier for amplification processing, and Returning the piezoelectric element; a microprocessor having more than one input end and more than one output end, the input end of which is connected to the output end of the signal processing circuit via an analog-to-digital converter; the microprocessor has a built-in a reference value of the measured value and the function of the tuning fork resonant groove frequency compensation and an action threshold adjusting unit, the action threshold adjusting unit provides a frequency threshold (Frequency Threshold) reference point for the microprocessor as a basis for judgment; The measuring device generates a sensing signal after the piezoelectric element resonates, and sends the signal to the filter in the signal processing circuit to filter out the noise and amplify After being amplified, it is sent to a clock signal converted into a digital form by an analog digital converter, and the signal processed by the signal processing circuit is sent to the piezoelectric element, and is also fed back to the piezoelectric element; After the clock signal, a corresponding tuning fork resonance frequency is calculated. When the material in the trough is in contact with the tuning fork, different resonance frequencies are generated and sent back to the microprocessor, whereby the microprocessor can obtain the The slope of the resonant frequency, and the slope is used to convert the specific gravity of the material in the trough, and then according to the built-in weight value of the microprocessor and the function of the tuning fork resonant groove frequency compensation, the threshold of the operating threshold is adjusted. The initial value is compensated so that the switching signal can be sent by the output circuit when the material contacts the same sensing point position on the tuning fork. The above device can automatically determine the specific gravity of the material, and then automatically compensate the correction frequency threshold, so that the judgment of the material level is more accurate and stable.

The above-mentioned tuning fork type sensing device for automatically adjusting the frequency threshold and the detecting point has a piezoelectric element including one or more piezoelectric sheet combinations, a piezoelectric element driving circuit and a piezoelectric signal receiving circuit.

The aforementioned tuning fork sensing device for automatically adjusting the frequency threshold and the detecting point, wherein the filter is a band pass filter.

Another object of the present invention is to provide a method for automatically adjusting a frequency threshold and a sensing point, which is mainly for a microprocessor to perform the following steps, including: reading an input frequency threshold reference point; and obtaining a tuning fork electrical and mechanical resonance backhaul Sensing frequency value; comparing the frequency threshold reference point and the sensing frequency value; when the sensing frequency value is less than the frequency threshold reference point, outputting a first control signal; otherwise, the sensing frequency value is not less than the frequency threshold reference point, Then output a second control signal; repeat the foregoing steps.

The invention utilizes the provided tuning fork type sensing device and method for automatically adjusting the frequency threshold and the detection point, and the specific benefit that can be obtained is that the microprocessor of the invention can offset the resonance frequency of the tuning fork according to the specific gravity of the material, so that the specific gravity Different materials have the same sensing position, which is easier to use and improves measurement accuracy and output stability.

Compared with the US Patent Publication No. US2006/0053863A1, the present invention has the following advantages in sensing the point threshold and the sensing point position:

In order to understand the technical features and practical functions of the present invention in detail, and in accordance with the contents of the specification, the following is a detailed description of the preferred embodiment as illustrated in the following: the automatic adjustment of the frequency threshold and the detection point provided by the present invention A preferred embodiment of the tuning fork type sensing device is first shown in FIG. 1 and FIG. 2, and includes a tuning fork 10 and a signal processing module 20. The tuning fork 10 has a sensing position S; the signal The processing module 20 includes a piezoelectric element 21, a signal processing circuit 22, a microprocessor 23, and an output circuit 24.

The piezoelectric element 21 is mainly in contact with the tuning fork 10; as shown in FIG. 3, the piezoelectric element 21 includes one or more piezoelectric sheet assemblies 211, a piezoelectric element driving circuit 212, and a piezoelectric signal receiving circuit 213. The piezoelectric element driving circuit 212 mainly deforms the piezoelectric sheet assembly 211 to generate a sine wave signal. The main material of the piezoelectric sheet assembly 211 is a piezoelectric film. The piezoelectric signal receiving circuit 213 includes a signal processing circuit in addition to receiving the sine wave signal, and is sent to the signal processing circuit 22 after receiving the signal; Referring to FIG. 2, the signal processing circuit 22 is mainly composed of a band pass filter 221 and an amplifier 222. The input end of the band pass filter 221 is connected to the output end of the piezoelectric signal receiving circuit 213. The input end and the output end of the amplifier 222 are respectively connected to the output end of the band pass filter 221 and the input end of the piezoelectric element 21, and the output end of the amplifier 222 is further connected to the microprocessor 23 via an analog converter 223. The input terminal is connected to the input terminal of the piezoelectric element drive circuit 212.

Referring to FIG. 4, the microprocessor 23 is mainly composed of a micro control unit 231, an action threshold adjustment unit 232, and a two-wire output control circuit 233. The micro control unit 231 has a built-in object to be tested. The value is proportional to the function of the tuning fork resonant groove frequency compensation, and the micro control unit 231 is connected to the output of the signal processing circuit 22 through the analog digital converter 223.

When the piezoelectric signal receiving circuit 213 sends the sensed sine wave signal to the signal processing circuit 22, the noise is first removed by the band pass filter 221, then the signal is amplified by the amplifier 222, and then transmitted through the analog digital converter 223. Analog-to-digital conversion to obtain a clock signal, and then sent to the microprocessor 23, the microprocessor 23 calculates the corresponding tuning fork resonance frequency, because the microprocessor 23 has a built-in specific value of the object to be measured and the tuning fork resonance concave The slot frequency compensation function is compared with the frequency threshold reference point input by the action threshold adjustment unit 232 according to the calculated tuning fork resonance frequency, and then the output of the output circuit 24 is obtained. In addition, in addition to transmitting the signal to the microprocessor 23, the output signal of the amplifier 222 is also fed back to the piezoelectric element drive circuit 212 of the piezoelectric element 21.

The signal judging process of the microprocessor 23 is as shown in FIG. 5, first reading the frequency threshold (Frequency Threshold) reference point Fref (501) input by the action threshold adjusting unit 232, and detecting the frequency of the clock signal returned by the tuning fork electromechanical resonance. The value Fsen(502) further compares the frequency threshold reference point Fref with the sensed frequency value Fsen obtained by the tuning fork frequency discrimination (503), and outputs a first control when the sensing frequency value Fsen is less than the frequency threshold reference point Fref. Signal (Output: ON) (504); otherwise, output a second control signal (Output: OFF) (505), and then repeat the foregoing steps to continue to discriminate the tuning fork signal.

Furthermore, the function data of the built-in value of the object to be tested and the frequency compensation of the tuning fork resonance groove can be obtained from the relationship between the resonance frequency and the depth of the material as shown in FIG. The function data can be a polynomial, an exponential pattern, a parabolic type, a linear function or a lookup table.

It can be seen from the above that the present invention can automatically determine the specific gravity of the material by using the foregoing device, thereby automatically compensating the corrected frequency threshold, and can adjust various specific gravity materials to the same position at the sensing position of the tuning fork 10, which is more convenient to use and makes the material level. The judgment is more accurate and stable.

The above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any one of ordinary skill in the art can use the present invention without departing from the technical features of the present invention. Equivalent embodiments of the present invention may be made without departing from the technical features of the present invention.

10. . . tuning fork

20. . . Signal processing module

twenty one. . . Piezoelectric element

211. . . Piezoelectric combination

212. . . Piezoelectric element driving circuit

213. . . Piezoelectric signal receiving circuit

twenty two. . . Signal processing circuit

221. . . filter

222. . . Amplifier

223. . . Analog digital converter

twenty three. . . microprocessor

231. . . Micro control unit

232. . . Action threshold adjustment unit

233. . . Two-wire output control circuit

twenty four. . . Output circuit

70. . . tuning fork

1 is a schematic diagram of a tuning fork in accordance with a preferred embodiment of the present invention.

2 is a block diagram of a circuit in accordance with a preferred embodiment of the present invention.

Figure 3 is a block diagram of a piezoelectric element in accordance with a preferred embodiment of the present invention.

4 is a block diagram of a microprocessor in accordance with a preferred embodiment of the present invention.

Figure 5 is a flow chart showing the operation of a preferred embodiment of the present invention.

Figure 6 is a graph showing the characteristic data of a function of a preferred embodiment of the present invention.

Figure 7 is a schematic diagram of the sensing position of the existing tuning fork.

20‧‧‧Signal Processing Module

21‧‧‧Piezoelectric components

22‧‧‧Signal Processing Circuit

221‧‧‧ filter

222‧‧‧Amplifier

223‧‧‧ Analog Digital Converter

23‧‧‧Microprocessor

24‧‧‧Output circuit

Claims (4)

A tuning fork type sensing device for automatically adjusting a frequency threshold and a detection point, comprising: a tuning fork body and a signal processing module; wherein the signal processing module comprises: a piezoelectric element, which is in contact with the tuning fork body; and a signal processing The circuit is mainly composed of a filter and an amplifier, and the filter receives the sensing signal sent from the piezoelectric element and sends it to the amplifier for amplification processing and returns to the piezoelectric element; a microprocessor having more than one An input end and one or more output ends, wherein the input end is connected to an output end of the signal processing circuit via an analog-to-digital converter; the microprocessor is mainly composed of a micro control unit, an action threshold adjustment unit and a two-wire output The control circuit is composed of a control unit, wherein the micro-control unit has a function data for calculating the specific value of the object to be measured and the frequency compensation of the tuning fork resonant groove, and the action threshold adjusting unit provides a frequency threshold (Frequency Threshold) reference point for the microprocessor. As a basis for the judgment; the microprocessor is further connected to an output circuit. The tuning fork type sensing device for automatically adjusting a frequency threshold and a detection point according to the first aspect of the patent application, wherein the piezoelectric element comprises more than one piezoelectric sheet combination, a piezoelectric element driving circuit and a piezoelectric signal receiving Circuit. The tuning fork type sensing device for automatically adjusting the frequency threshold and the detecting point according to the second aspect of the patent application is a band pass filter. The tuning fork type sensing device for automatically adjusting the frequency threshold and the detecting point according to the third item of the patent application scope, wherein the weight of the object to be measured and the function of the tuning fork resonant groove frequency compensation are polynomial, exponential type, parabolic type , linear function or lookup table.