CN204514512U - Based on the pressure unit of LC oscillatory circuit - Google Patents

Abstract

The utility model discloses a kind of pressure unit based on LC oscillatory circuit, comprise the pressure-displacement converted mechanism, LC sine wave oscillation circuit, frequency measuring instrument, A/D change-over circuit, single-chip microcomputer and the display that connect successively, described pressure-displacement converted mechanism comprises pressure plare and is arranged on the measuring coil below pressure plare, and described measuring coil is connected in LC sine wave oscillation circuit.It is frequency values that the utility model measures the signal exported, then by calculating shift value, even if voltage signal size changes, as long as voltage signal frequency does not change, measurement result would not change, and therefore has higher sensitivity, the linearity and anti-interference.

Description

Based on the pressure unit of LC oscillatory circuit

Technical field

The utility model relates to measuring instrument technical field, particularly a kind of pressure unit.

Background technology

Along with industrial development, requirements at the higher level are proposed to the measuring accuracy of measuring instrument, measurement range, dynamic perfromance and long-distance transmissions etc.At present, the delivering method of domestic pressure signal mainly contains inductance type, condenser type, force balance type, Hall-type, type vibration wire, strain-type and optical fiber type etc. according to principle of work.Wherein the principle of work of inductance pressure transducer is because magnetic material is different with magnetic permeability, when pressure acts on diaphragm, size of gaps changes, the change of air gap affects the change of coil inductance, treatment circuit can change into corresponding electric signal the change of this inductance and export, thus reaches the object measuring pressure; The advantage of inductance pressure transducer can carry out long-distance transmissions; But linear not too high, and if whole system is if there is disturbance, such as supply voltage rising etc., so measurement result also there will be fluctuation.Mechanical compression instrument can only carry out In situ Measurement, and can not carry out remote transmission, easy fault, measuring accuracy is low.

Utility model content

The utility model technical issues that need to address are to provide all higher pressure unit of a kind of sensitivity, the linearity, accuracy and anti-interference.

For solving the problems of the technologies described above, technical solution adopted in the utility model is as follows.

Based on the pressure unit of LC oscillatory circuit, comprise the pressure-displacement converted mechanism, LC sine wave oscillation circuit, frequency measuring instrument, A/D change-over circuit, single-chip microcomputer and the display that connect successively, described pressure-displacement converted mechanism comprises pressure plare and is arranged on the measuring coil below pressure plare, and described measuring coil is connected in LC sine wave oscillation circuit.

The above-mentioned pressure unit based on LC oscillatory circuit, described pressure plare is high-strength plastic flitch.

The above-mentioned pressure unit based on LC oscillatory circuit, described LC sine wave oscillation circuit comprises electric capacity, telefault, triode and current-limiting resistance; The two ends of described measuring coil are connected in the two ends of electric capacity in LC sine wave oscillation circuit in parallel, and measuring coil is coupled with the telefault in LC sine wave oscillation circuit by iron core; The base stage of one end connecting triode of described telefault, the other end ground connection of telefault; The parallel branch of measuring coil and electric capacity is connected between power supply and the collector of triode; Current-limiting resistance is connected between the emitter of triode and ground.

The above-mentioned pressure unit based on LC oscillatory circuit, dividing potential drop branch road is also provided with in described LC sine wave oscillation circuit, described dividing potential drop branch road comprises and is connected in series in the first resistance between VDD-to-VSS and the second resistance, and the base stage of triode is connected between the first resistance and the second resistance.

The above-mentioned pressure unit based on LC oscillatory circuit, be also provided with filter capacitor in described LC sine wave oscillation circuit, filter capacitor is connected between telefault and transistor base.

Owing to have employed above technical scheme, acquired by the utility model, technical progress is as follows.

Pressure signal is converted into displacement signal by the utility model, and this displacement causes coil inductance to change, by measuring the frequency of LC oscillatory circuit output signal and then can going out pressure size by indirect inspection.Relative to direct inductance type pressure unit, it is frequency values that the utility model measures the signal exported, then by calculating shift value, even if voltage signal size changes, as long as voltage signal frequency does not change, measurement result would not change, and therefore has higher sensitivity, the linearity and anti-interference.

Accompanying drawing explanation

Fig. 1 is structured flowchart of the present utility model;

Fig. 2 is the structural representation of pressure-displacement converted mechanism described in the utility model;

Fig. 3 is the circuit diagram of LC sine wave oscillation circuit described in the utility model.

Wherein: 8. pressure plare; L. measuring coil, C. electric capacity, L _b. telefault, Q. triode, R _e. current-limiting resistance, C _b. filter capacitor C _b, R _b1. the first resistance, R _b2. the second resistance.

Embodiment

Below in conjunction with the drawings and specific embodiments, the utility model is further elaborated.

The utility model can only carry out In situ Measurement for the mechanical compression instrument measuring pressure at present, and can not carry out remote transmission, easy fault, measuring accuracy is low; Other inductance types, capacitive pressure instrument, although can realize the remote transmission of pressure, its measuring accuracy is lower, and the aspect Problems existing such as (as mains fluctuations) that is easily interfered when measuring, improve.The amount of measurement is transformed into frequency from curtage by the utility model, not only can improve measuring accuracy and sensitivity, but also can improve antijamming capability.

The utility model provides a kind of pressure unit based on LC oscillatory circuit, as shown in Figure 1, comprises the pressure-displacement converted mechanism, LC sine wave oscillation circuit, frequency measuring instrument, A/D change-over circuit, single-chip microcomputer and the display that connect successively.

As shown in Figure 2, the measuring coil L comprising pressure plare 8 and be arranged on below pressure plare, measuring coil L is connected in LC sine wave oscillation circuit pressure-displacement converted mechanism.Pressure plare selects high-strength plastic flitch, does not affect Distribution of Magnetic Field, and measuring coil selects multilayer inductor, and two connection terminals, in the same side, are convenient to circuit and are connected.

The circuit diagram of LC sine wave oscillation circuit of the present utility model as shown in Figure 3, comprises electric capacity C, telefault L _b, triode Q, current-limiting resistance R _e, dividing potential drop branch road and filter capacitor C _b.The two ends of measuring coil L are connected in the two ends of electric capacity C in LC sine wave oscillation circuit in parallel, and measuring coil L is by the telefault L in iron core and LC sine wave oscillation circuit _bcoupling.Telefault L _bone end through filter capacitor C _bthe base stage of connecting triode Q, telefault L _bother end ground connection; The parallel branch of measuring coil L and electric capacity C is connected to power supply U _eand between the collector of triode Q; Current-limiting resistance R _ebetween the emitter being connected to triode Q and ground.Dividing potential drop branch road comprises and is connected in series in power supply U _eand the first resistance R between ground _b1 and the second resistance R _bthe base stage of 2, triode Q is connected to the first resistance R _b1 and the second resistance R _bbetween 2.

Principle of work of the present utility model is: when pressure is applied on pressure plare, and due to pressure effect, compression measuring coil, causes measuring coil length to shorten, namely change the inductance value size of measuring coil; When the inductance value of measuring coil changes, namely the resonance frequency of LC sine wave oscillation circuit changes, and due to the change of resonance frequency, the output frequency of whole LC sine wave oscillation circuit also will change thereupon.The oscillation frequency situation of change of LC sine wave oscillation circuit is measured by frequency measuring instrument, and by being transferred to single-chip microcomputer after the conversion of A/D change-over circuit, single-chip microcomputer, according to survey frequency, utilizes the relation of frequency and pressure P, calculate pressure values P, then shown by display.

The relation of institute's measuring pressure and frequency in the utility model, calculates by air-core inductance computing formula, frequency computation part formula and Hooke's law, makes a concrete analysis of as follows.

Air-core inductance computing formula:

$L=\frac{0.01\mathrm{DN}}{\frac{l}{D}+0.44}$

In formula: L---air cored coil inductors, D---air core coil diameter (cm), the N---air core coil number of turn (circle), l---air core coil length (cm).

Frequency computation part formula:

$f=\frac{2}{2\mathrm{\π}\sqrt{\mathrm{LC}}}$

In formula: f---LC oscillatory circuit frequency (Hz), C---LC oscillatory circuit electric capacity (F).

Hooke's law: PS=kx

In formula: P---institute pressure measurement powerful little (Pa), S---pressure measurement area (m2), the stiffness factor (N/m) of k---spring air core coil, spring coil displacement (m) under x---P pressure.

The pass that to sum up can obtain frequency change and pressure is:

$\mathrm{\Δf}\≈\frac{{10}^4\mathrm{PS}}{4\mathrm{kND}(l+0.44D)\sqrt{C}}$

LC oscillatory circuit difference on the frequency (Hz) before and after △ f---changes.

As can be seen here, when system is determined, k, D, N, l, C are constant, and frequency change and absolute pressure are approximately linear relationship, and therefore the utility model can measure by the change of survey frequency the force value be applied on pressure plare.

Certainly, the utility model can also by range and the sensitivity selecting the inductance measuring of different stiffness factor to change pressure unit.

Claims (5)

1. based on the pressure unit of LC oscillatory circuit, it is characterized in that: comprise the pressure-displacement converted mechanism, LC sine wave oscillation circuit, frequency measuring instrument, A/D change-over circuit, single-chip microcomputer and the display that connect successively, described pressure-displacement converted mechanism comprises pressure plare (8) and is arranged on the measuring coil (L) below pressure plare, and described measuring coil (L) is connected in LC sine wave oscillation circuit.

2. the pressure unit based on LC oscillatory circuit according to claim 1, is characterized in that: described pressure plare is high-strength plastic flitch.

3. the pressure unit based on LC oscillatory circuit according to claim 1, is characterized in that: described LC sine wave oscillation circuit comprises electric capacity (C), telefault (L _b), triode (Q) and current-limiting resistance (R _e); The two ends of described measuring coil (L) are connected in the two ends of electric capacity (C) in LC sine wave oscillation circuit in parallel, and measuring coil (L) is by the telefault (L in iron core and LC sine wave oscillation circuit _b) coupling; Described telefault (L _b) the base stage of one end connecting triode (Q), telefault (L _b) other end ground connection; The parallel branch of measuring coil (L) and electric capacity (C) is connected between the collector of power supply and triode (Q); Current-limiting resistance (R _e) be connected to triode (Q) emitter and ground between.

4. the pressure unit based on LC oscillatory circuit according to claim 3, is characterized in that: be also provided with dividing potential drop branch road in described LC sine wave oscillation circuit, and described dividing potential drop branch road comprises the first resistance (R be connected in series between VDD-to-VSS _b1) and the second resistance (R _b2), the base stage of triode (Q) is connected to the first resistance (R _b1) and the second resistance (R _b2) between.

5. the pressure unit based on LC oscillatory circuit according to claim 3, is characterized in that: be also provided with filter capacitor (C in described LC sine wave oscillation circuit _b), filter capacitor (C _b) be connected to telefault (L _b) and triode (Q) base stage between.