CN1268666A - Frequency measurement and cycle measurement based integrated signal detection and processing method - Google Patents

Abstract

The present invention relates to the detection method of parameters such as temp. moisture etc. it mainly includes: (1) convert the change of resistance or capacitance of sensor directly into frequency signal change; (2) use the measuring method of frequency signal based on integrated frequency detection and cycle detection; (3) use multi time insertion method to obtain sensing characteristics curve under different environment. The measuring and controlling instrument designed by resent invention simplifies the detecting and measuring method, it is strong in anti interference ability, high in measuring precision and stability, broad in measuring range and can be used in remote measuring.

Description

Based on frequency measurement and cycle measurement integrated input and disposal route

The present invention relates to input and disposal route, specifically be meant a kind ofly be applicable to parameter detecting such as resistance, capacitive based humidity, temperature, based on frequency measurement and cycle measurement integrated input and disposal route.

Very extensive to the application of parameter measurements such as temperature, humidity in industrial and agricultural production, scientific research and daily life.The input and the disposal route of measurement and control instruments such as common resistance, capacitive based humidity, temperature, its main points are resistance or the capacitance variation that temperature, the isoparametric variable signal of humidity converted to senser element, utilize translation circuit to convert resistance or capacitance variation to voltage signal output again, after rectification, amplification, signal adjustment and A/D conversion etc., send microprocessor to analyze and handle.This method link is more, antijamming capability relatively poor (adopting the analog quantity processing and amplifying), unless adopt special-purpose amplifying device, for the bigger situation of measured variation range, the sort signal treatment circuit is difficult to satisfy Testing requirement.

The objective of the invention is to overcome the existing problems of above-mentioned prior art, propose a kind ofly, be used for the design and the exploitation of parameter investigating instruments such as resistance, capacitive based humidity, temperature based on frequency measurement and cycle measurement integrated input and disposal route.

Realize that purpose of the present invention comprises three main contents:

1. resistance or the capacitance variations with senser element is directly changed into the frequency signal variation

Temperature-sensitive, wet Sensitive Apparatus such as quick change measured parameter and convert resistance or changes in capacitance to, and Sensitive Apparatus directly inserts in the oscillatory circuit, and the oscillatory circuit output signal frequency then is the resistance of corresponding device or the function of electric capacity;

2. adopt measuring method based on the frequency signal of frequency measurement and cycle measurement integrated approach

According to the size of measured signal frequency, guarantee under the prerequisite of measuring accuracy and rapidity, at the high band employing frequency measurement method of measured signal, in the low-frequency range employing periodic measurement methods of signal;

3. use repeatedly method of interpolation, draw the sensing characteristics curve under the varying environment

Change with also relevant with other multiple environmental factors outside the Pass measured amount has at Sensitive Apparatus parameter sometimes, the mathematical method of using repeatedly interpolation changes into several two-dimensional problems to the problem of a multidimensional, obtains the sensing characteristics curve under the varying environment.

The present invention compared with prior art has following characteristic and innovation part: 1. with sensor to resistance or the isoparametric variation of electric capacity directly be transformed into frequency signal and change, the sort signal detection method has that peripheral circuit is simple, antijamming capability is strong, be beneficial to remote measurement, the wide characteristics of measurement range, is specially adapted to resemble the measurement of the physical quantity that time constant is big, variation range is wide of humidity, this class of temperature; 2. the detection of frequency signal adopts the integrated method of frequency measurement and cycle measurement to carry out, and guarantees measuring accuracy and rapidity simultaneously; 3. in the data processing, the mathematical method of using interpolation changes into a plurality of two-dimensional problems dexterously to the problem of a multidimensional, and it can eliminate a plurality of non-measured parameter well to the influence of sensing accuracy and the nonlinear problem of solution senser element.

Fig. 1 detects and the disposal route theory diagram based on the integrated transducing signal of frequency measurement and cycle measurement;

Fig. 2 is damp-warm syndrome degree sensing resistance translation circuit figure frequently;

Fig. 3 is macromolecule wet bulb thermometer (instrument) temperature compensation schematic diagram;

Fig. 4 is the main program structure block diagram.

To be further described the present invention by embodiment and accompanying drawing thereof below:

The theory diagram of the high molecular resistance type wet bulb thermometer (instrument) (hereinafter to be referred as wet bulb thermometer (instrument)) of employing the present invention development as shown in Figure 1.Among Fig. 1, high molecular resistance type wet sensitive device R _HBe used for humidity sensor, thermistor R _TBe used for temperature sensing, R _H, R _TWith resistance frequency translation circuit shown in Figure 2 tested humidity and temperature signal directly are transformed into frequency signal, the two-way frequency signal switches link by photoelectricity coupling and passage and carries out the photoelectricity isolation, and by software gating wherein a tunnel, this signal is sent into Single Chip Microcomputer (SCM) system through the shaping link, two timer sum counters by single-chip microcomputer inside cooperate, finish the frequency or the cycle of input signal are measured, be converted into frequency values by software again.By taking turns gating temperature and humidity signal, just can obtain the frequency values of the humidity and the temperature of corresponding current measurand.Data processor is by twice interpolation, and not only compensation is because variation of temperature and influence that sensor performance is caused, and the nonlinear problem of moisture sensor also obtains satisfactory solution, thus the temperature factor influence that has been eliminated, humidity value comparatively accurately.

Fig. 2 is the resistance frequency translation circuit figure of wet bulb thermometer (instrument): in Fig. 2, and R _HBe the wet sensitive device of high molecular resistance type, R _TBe common NTC type GC-C103 thermistor.Wet sensitive device R _HCan equivalent singly-terminal pair (R for the resistance capacitor device mixing _S, C _S), the resistance frequency translation circuit that utilizes two 555 timers to constitute is converted to two-way frequency signal f to the resistance of wet sensitive device with the variation of humidity and the resistance of thermistor with variation of temperature respectively _HAnd f _TExperiment and mathematical analysis all show circuit integrating capacitor C _QValue must be less than the equivalent capacity C of wet sensitive device _SResistance frequency converter circuit over half could work; By to R ₁And C _QChoose reasonable, can guarantee that sensing characteristics not only has monotonicity but also good sensitivity is arranged.

At C _S〉=2 _CQCondition under, the frequency of humidity passage output f _H=1/T _H, T _HCan be calculated as follows: $T_H=A\ln \frac{B-0.6}{B-0.3}+D\ln \frac{2V_{\∝}-B}{V_{\∝}-B}---\left(1\right)$

In the formula:

R ₁, R ₂, R _S, C _SAnd C _QAs shown in scheming to go up.And the frequency of temperature channel oscillatory circuit output f _T=1/T _T, T _TCan be calculated as follows:

T _T＝0.693(R ₃+2R _T)C ₄ (2)

In the formula: R ₃, C ₄As shown in the figure, R _TBe thermistor.

Because the resistance variations scope of humidity sensitive device big (reaching several magnitude), the also corresponding broad of output signal frequency scope after the resistance conversion frequently (several to the hundreds of thousands hertz) adopts single frequency measuring method or survey Zhou Fangfa to carry out signal measurement and all is difficult to guarantee precision.Adopted the integrated measuring method of frequency measurement and cycle measurement in the present embodiment.Practice shows that the precision of the signal detecting method that frequency measurement and cycle measurement is integrated and stability are all better, is specially adapted to high performance humiture and detects.

The way of the concrete enforcement of twice interpolation method of data processing is as follows:

1. as shown in Figure 3, in the measurement range of hygrometer (instrument), measuring the humidity source according to national standard is X ₀, X ₁... X _iX _NThe time in temperature t _k(k=0,1 ... M) under, corresponding signal voltage value V _{I, k}(i=0,1 ... N) value has so just obtained M+1 group data (every group of corresponding 1 humidity characteristic curve of number).Temperature subregion point t ₀, t ₁... t _kT _MWith humidity subregion point X ₀, X ₁... X _iX _NAnd the M+1 that records above group data, store successively according to a definite sequence and to be cured in the Single Chip Microcomputer (SCM) system EPROM, finish the work of setting up of database.

2. after Single Chip Microcomputer (SCM) system is measured temperature t, establish t ₀≤ t≤t _M, with t and temperature subregion point t ₀, t ₁... t _kT _MCompare, find out the temperature range [t at t place _K-1, t _k], k ∈ [1, M], thus obtain in temperature t _K-1And t _kTwo groups of humidity characteristic data, the humidity point X of correspondence on the humidity characteristic curve when utilizing following formula just can calculate temperature t again ₀, X ₁... X _iX _NMagnitude of voltage V _{0, t}, V _{1, t}... V _{I, t}... V _{N, t} $V_{i,t}=V_{i,k-1}+\frac{V_{i,k}-V_{i,k-1}}{t_k-t_{k-1}}(t-t_{k-1})---(i=\mathrm{0,1},\…N)$

3. measure humidity sensor magnitude of voltage V by Single Chip Microcomputer (SCM) system, V and the magnitude of voltage V that tried to achieve just now _{0, t}, V _{1, t}... V _{I, t}... V _{N, t}(V under the normal condition compares _{0, t}≤ V≤V _{N, t}).If V _{I-1, t}≤ V≤V _{I, t}, obtain then having that humidity value is under the temperature compensation: $X=X_{i-1}+\frac{V-V_{i-1,t}}{V_{i,t}-V_{i-1,t}}(X_i-X_{i-1})$

By means of the actual limited several groups of humidity sensing characteristic curves of measuring, try to achieve sensing characteristics curve calculation formula under the arbitrary temp by interpolation method, eliminated the influence of temperature to sensor performance, solved the nonlinear problem of sensing characteristics.

The software of wet bulb thermometer (instrument) has adopted structuring and modular design, realizes the integrated main program block diagram of frequency measurement and cycle measurement method as shown in Figure 4.Main functional modules has: main program module, timer interrupt sum counter interrupt module, display module, keyboard monitoring module, serial communication module, print module and output control module etc.

The function that software main program is realized has: the initialization of system; Calculated rate value after the sampling of timer sum counter paired pulses is finished; Select frequency measurement or period measurement according to measured value; The switching of control survey passage is in turn to humidity and temperature channel sampling; Accounting temperature value and humidity value are also selected displays temperature or humidity according to the user; The timer sum counter is reinitialized and starts next round sampling etc.Timer interrupts the sum counter interrupt module to be realized the frequency of signal or the measurement in cycle.Display module, keyboard monitoring module responds user's input also selects to show measurement result according to the user.The serial communication module sends to host computer (PC or industrial computer etc.) by serial port with measurement result and accepts the instruction of host computer.Print module is printed measurement result, output control module is except that humidity and temperature no to scale are distinguished the output signal, keyboard input setting value according to host computer or user, each can on-the-spotly set 4 points (value) in measurement range, be about to measurement range and be divided into 5 intervals, system software compares Current Temperatures, humidity value and the setting value that records, by coding form (8421 yards) output currency place block information (Transistor-Transistor Logic level).Just can obtain the temperature and humidity control signal by corresponding external decoding and driving circuit.

Claims (1)

1,, it is characterized in that this law comprises following three main contents based on frequency measurement and cycle measurement integrated input and disposal route:

1. resistance or the capacitance variations with senser element is directly changed into the frequency signal variation

Temperature-sensitive, wet Sensitive Apparatus such as quick change measured parameter and convert resistance or changes in capacitance to, and Sensitive Apparatus directly inserts in the oscillatory circuit, and the oscillatory circuit output signal frequency then is the resistance of corresponding device or the function of electric capacity;

2. adopt measuring method based on the frequency signal of frequency measurement and cycle measurement integrated approach

According to the size of measured signal frequency, under the prerequisite that guarantees measuring accuracy and rapidity, at the high band employing frequency measurement method of measured signal, in the low-frequency range employing periodic measurement methods of signal;

3. use repeatedly method of interpolation, draw the sensing characteristics curve under the varying environment

Change with also relevant with other multiple environmental factors outside the Pass measured amount has at Sensitive Apparatus parameter sometimes, the mathematical method of using repeatedly interpolation changes into several two-dimensional problems to the problem of a multidimensional, obtains the sensing characteristics curve under the varying environment.

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