CN1308225A - Fast prediction thermometer based on new temperature measuring principle - Google Patents

Abstract

The fast prediction type thermometer based on new temperature-measuring principle contains temperature sensor, high input impedence, low-noise and low-drift amplifier, AD converter, monochip computer and digital display. It does not use heat balance principle as basis, and utilizes the temperature detection value derived from heat transfer equation and taken out from heating-up curve including every heat parameter in the heat transfer system and derivative value corresponding to said temperature value to fast calculate the deep temperature of tested body surface. Said invention can be used for fast measuring surface temp. of tested body and its temperalure distribution, and for making short-period temperature change prediction of some temperature system, can also be used in the temperature control process of temperature control system with vibration free requirement.

Description

Fast prediction thermometer based on new temperature measuring principle

The present invention relates to a kind of temperature measuring equipment, particularly a kind of fast prediction thermometer based on new temperature measuring principle.It is from measuring the Temperature numerical and the respective derivative value at diabatic process initial stage, prune and be included in system's thermal parameter such as the quality of temperature probe, the lumped parameter quality for the treatment of the thermometric thing and the two corresponding specific heat capacity in these measurable variables, thermometer and by thermal coupling parameter between the thermometric thing etc., thereby rely on minority temperature detection data, the extrapolated fast deep layer place, thermometric thing surface that treats stablizes the thermometer of the general type contact thermography of constant temperature.

In the contact thermography process, people always carry out temperature survey according to heat balance principle.Be that thermometer contacts long enough after the time with treating the thermometric object, the two temperature equates, according to thermometer itself certain and the temperature variation of characterisitic parameter one to one, indicates the numerical value of thermometer self-temperature.The Temperature numerical that obtains with this temp measuring method and the characteristic and the thermometer of thermo detector and treat that the way of contact between the thermometric thing is irrelevant, promptly irrelevant, irrelevant with the mode of thermometric with used thermometer.According to the thermometer that heat balance principle is made, all be the general type thermometer.

Improve thermometric speed, have only the quality and the specific heat capacity that 1. reduce thermometer,, the temperature of thermometer is changed rapidly to reduce the thermal inertia of thermometer based on the thermometer of heat balance principle; 2. strengthen thermometer and treat thermal coupling between the thermometric thing, to strengthen the heat transfer capacity in the unit interval, shortening heat conductive process.But the indication instability of this class thermometer is easy to indicate different temperature values under the condition of environment temperature minor alteration.So the thermometer with the way that changes above-mentioned two class conditions was made with the shortening thermometric time has not just had practical value later on to certain limit.

In order to shorten the thermometric time of contact-type temperature measuring equipment significantly, when people once utilized temperature sensor and treated that the thermometric object contacted, some temperature spots that in the temperature changing process of temperature sensor, record, utilize the powerful calculating ability of computing machine again, do the curve fitting of temperature rise curve, use the extrapolated temperature eventually of matched curve again, as described in document US 4541734, the EP 0338076 etc.Exactly because be to do the full curve match, in order to reduce measuring error, must in bigger interval, make multi-point sampling, this makes that Measuring Time can not be very short; Temperature sensor and treat that the duration of contact between the thermometric thing is longer, less for those specific heat capacities, quality is less treats will to be directed at the thermometric thing the bigger decline of temperature, thereby to draw the state equation that another describes the determinand temperature.Problem has become the simultaneous solution temperature sensor and has treated the Simultaneous Equations of two states of thermometric thing, makes problem complicated more, and calculated amount increases.Gone through this situation in the document EP 0338076.In addition, owing to employed the more expensive computing machine of price, thus be unfavorable for its being extensive use of as common temperature measurement tool.

Mentality of designing of the present invention is, when the temperature probe of thermometer when treating that the thermometric thing contacts, if the temperature of the two is unequal, just have the transmission of heat, make the temperature of probe change.The shape of probe temperature rise curve has comprised these parameters by the two specific heat capacity, quality and the decision of the heat couple coefficient between the two in the temperature rise curve.Thereby can replace these parameters with the minority measured value on the temperature rise curve leading portion.Make the measured value of temperature and the characterisitic parameter that temperature is taken into account temperature thing to be measured have nothing to do, make this thermometer become the universality thermometer.And reached the purpose of quick temperature measurement.

The objective of the invention is not from heat balance principle and from diabatic process, do not do the match of full curve, and from describing the linear ordinary differential of diabatic process, in linear extrapolation, utilize the low volume data that from temperature rise curve, obtains, separately specific heat capacity, quality and mutual parameters such as heat couple coefficient in the cancellation heat transfer system, utilize cheap single-chip microcomputer to do simple calculating again, extrapolated temperature eventually.The accuracy that can simplify calculating, shorten detection time, improve the result is calculated in this linear extrapolation.

In order to achieve the above object, the technical basis of the fast prediction thermometer based on new temperature measuring principle of the present invention is: when temperature probe with a certain when treating that the thermometric object contacts, if the temperature of temperature probe is less than the temperature for the treatment of the thermometric object, and temperature probe is removed outside the small size that contacts with the determinand surface, remainder all covers heat insulation layer, with the thermal loss that reduces to pop one's head in to environment.Pop one's head in as shown in Figure 2, wherein 1 is temperature sensor, the 2nd, and lead-in wire, the 3rd, adiabatic head, the 4th, jacket, the 5th, spring, its keep sensor in testing process and the pressure between the measured object surface constant, constant to remain between two temperature detecting point the heat couple coefficient of the two, the 6th, handle.So the state of temperature of temperature probe is just by the linear ordinary differential equation of first order group: $m_1{\mathrm{<figure-callout\; id="1"\; label="c"\; filenames="A0110001300071.png"\; state="\{\{state\}\}">c</figure-callout>}}_1\frac{\mathrm{d\&theta;}}{\mathrm{dt}}=k_1(T_s-\mathrm{\&theta;})-k_2(\mathrm{\&theta;}-T)---\left(1\right)$ $m_2{\mathrm{<figure-callout\; id="2"\; label="c"\; filenames="A0110001300071.png"\; state="\{\{state\}\}">c</figure-callout>}}_2\frac{\mathrm{dT}}{\mathrm{dt}}=k_2(\mathrm{\&theta;}-T)---\left(2\right)$ Describe.T in the formula _sBe the temperature for the treatment of to have apart from the surface in the thermometric thing the inner place of certain depth, m ₁Be to treat thermometric thing surface and temperature probe surface of contact and apart from the lumped parameter quality of this surperficial certain depth vicinity one fritter object, c ₁Be the lumped parameter specific heat capacity of this fritter object, k ₁By depths, point for measuring temperature surface and treat heat couple coefficient between the point for measuring temperature surface, θ is the surface temperature of thermometric thing; m ₂Be the quality of temperature probe, c ₂Be the specific heat capacity of temperature probe, k ₂Be temperature probe and treat heat couple coefficient between the thermometric thing surface that T is the temperature of temperature probe.

(1) formula is deformed into $m_1{\mathrm{<figure-callout\; id="1"\; label="c"\; filenames="A0110001300071.png"\; state="\{\{state\}\}">c</figure-callout>}}_1\frac{\mathrm{d\&theta;}}{\mathrm{dt}}+({\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="A0110001300071.png"\; state="\{\{state\}\}">k</figure-callout>}}_1+k_2)\mathrm{\&theta;}=k_{2}T+k_1{T}_s$ Back redeformation is $k_{2}T+k_1{T}_s=m_1{c}_1{e}^{-\frac{{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="A0110001300071.png"\; state="\{\{state\}\}">k</figure-callout>}}_2+k_1}{m_2{c}_2}t}\frac{d}{\mathrm{dt}}\left[{\mathrm{<figure-callout\; id="2"\; label="e\; k"\; filenames="A0110001300071.png"\; state="\{\{state\}\}">e</figure-callout>}}^{\frac{k_{}}{}}\mathrm{\&theta;}\right];$ Then (2) formula is deformed into $m_2{c}_2{e}^{-\frac{k_2}{m_2{c}_2}t}\frac{d}{\mathrm{dt}}\left[e^{\frac{k_2}{m_2{c}_2}t}T\right]={\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="A0110001300071.png"\; state="\{\{state\}\}">k</figure-callout>}}_2\mathrm{\&theta;},$ With formula before the θ substitution in this formula, just obtain with

Second Order with Constant ordinary differential equation for argument: ${\left({\mathrm{<figure-callout\; id="1"\; label="e\; k"\; filenames="A0110001300071.png"\; state="\{\{state\}\}">e</figure-callout>}}^{\frac{k_{}}{}}\mathrm{\&theta;}\right)}^{\&prime;\&prime;}+(\frac{{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="A0110001300071.png"\; state="\{\{state\}\}">k</figure-callout>}}_1+k_2}{m_1{c}_1}-\frac{k_2}{m_2{c}_2}){\left({\mathrm{<figure-callout\; id="1"\; label="e\; k"\; filenames="A0110001300071.png"\; state="\{\{state\}\}">e</figure-callout>}}^{\frac{k_{}}{}}\mathrm{\&theta;}\right)}^{\&prime;}-\frac{{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="A0110001300071.png"\; state="\{\{state\}\}">k</figure-callout>}}_2^2}{m_1{m}_2{c}_1{c}_2}\left({\mathrm{<figure-callout\; id="1"\; label="e\; k"\; filenames="A0110001300071.png"\; state="\{\{state\}\}">e</figure-callout>}}^{\frac{k_{}}{}}\mathrm{\&theta;}\right)-\frac{k_1{k}_2{T}_s}{m_1{m}_2{c}_1{c}_2}{\mathrm{<figure-callout\; id="1"\; label="e\; k"\; filenames="A0110001300071.png"\; state="\{\{state\}\}">e</figure-callout>}}^{\frac{k_{}}{}}=0$ According to the general theory of ordinary differential equation, the function of this equation

Particular solution is arranged:

Or θ=T _sWith this particular solution substitution formula (2), the general solution that just can solve thermometer probe temperature equation is: $T={\mathrm{Ae}}^{-\frac{{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="A0110001300071.png"\; state="\{\{state\}\}">k</figure-callout>}}_1+k_2}{m_1{c}_4}t}+T_s---\left(3\right)$ A is an integration constant in the formula.T=T when starting condition is t=0 ₀So following formula can be write as: $T=T_0{\mathrm{<figure-callout\; id="1"\; label="e\; k"\; filenames="A0110001300071.png"\; state="\{\{state\}\}">e</figure-callout>}}^{\frac{k_{}}{}}+T_s(1-e^{-\frac{{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="A0110001300071.png"\; state="\{\{state\}\}">k</figure-callout>}}_1+k_2}{m_{1}c}t})---\left(4\right)$ But the characterisitic parameter such as the m that (4) have comprised many systems in the formula _i, c _i, k _i(i=1,2) is not easy to measure.In measurement, should seek other ways.

From (3) formula as can be seen, if at t ₁, t ₂It is T that two moment record temperature value ₁, T ₂, the numerical value of the derived function of temperature is T ₁', T ₂', then t has relation at any time: $\frac{{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="A0110001300071.png"\; state="\{\{state\}\}">T</figure-callout>}}_2^{\&prime;}-{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="A0110001300071.png"\; state="\{\{state\}\}">T</figure-callout>}}_1^{\&prime;}}{T^{\&prime;}-{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="A0110001300071.png"\; state="\{\{state\}\}">T</figure-callout>}}_1^{\&prime;}}=\frac{e^{\frac{k_2-k_1}{m_1{c}_1}{t}_2}-e^{\frac{k_2-k_2}{m_1{c}_1}{t}_1}}{e^{\frac{k_2-k_1}{m_1{c}_1}t}-e^{\frac{k_2-k_2}{m_1{c}_1}{\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="A0110001300071.png"\; state="\{\{state\}\}">t</figure-callout>}}_1}}=\frac{T_2-T_1}{T={\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="A0110001300071.png"\; state="\{\{state\}\}">T</figure-callout>}}_1},$ Thereby relation is arranged $T=\frac{T^{\&prime;}-{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="A0110001300071.png"\; state="\{\{state\}\}">T</figure-callout>}}_1^{\&prime;}}{{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="A0110001300071.png"\; state="\{\{state\}\}">T</figure-callout>}}_2^{\&prime;}-T_1}(T_2-T_1).$ When the temperature of time t → ∞ chronothermometer reaches stable final equilibrium temperature, promptly Temperature numerical is tending towards being parallel to the straight line T=T of transverse axis _∞, at this moment T is arranged _∞'=0, so obtain: $T_{t\&RightArrow;\&infin;}=T_{\&infin;}=T_s=\frac{{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="A0110001300071.png"\; state="\{\{state\}\}">T</figure-callout>}}_1^{\&prime;}}{{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="A0110001300071.png"\; state="\{\{state\}\}">T</figure-callout>}}_1^{\&prime;}-{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="A0110001300071.png"\; state="\{\{state\}\}">T</figure-callout>}}_2^{\&prime;}}(T_2-T_1)---\left(A\right)$ From (4) formula, allow t → ∞, also can directly obtain T _{T → ∞}=T _sThis result.So, just tried to achieve the temperature apart from certain depth place, determinand surface of object apace.

Fast prediction thermometer based on new temperature measuring principle of the present invention can demonstrate universality and very big superiority aspect other in temperature survey.It fast the Measuring Object surface temperature distribution, can the variation of predicted temperature quickly and accurately in the temperature control process, make system temperature stably along predetermined heating curve operation, also can make short-term temperature and become and predict the environment of temperature variation.

The present invention will be illustrated as shown in Figure 2 in conjunction with the accompanying drawings by embodiment.The Unit three that the zero point drift of signal process, temperature drift and the time drift that temperature sensor 1 is sent is all very little or the computing instrumentation amplifier 2 of a unit carry out impedance conversion and amplification, adjust its enlargement factor, make the numerical value of its output equal correct temperature value.Again this temperature simulation amount is sent into AD converter 3 and converted the analog quantity of this temperature value to digital quantity and send into single-chip microcomputer 4 later on and carry out the calculating of Temperature numerical, show result calculated by nixie display 5 at last.These all are proven technique very.

Data with actual measurement are done numerical differentiation, and certain trouble is arranged technically.Carrying out numerical evaluation should use AD converter to convert analog quantity to digital quantity in order to calculating earlier.So it is too little that the mistiming between two sampling values can not be obtained, otherwise in the factor value differential calculation subtraction is arranged, the numerical value between two temperature sampling values is very approaching, does the effective value that will cause operation result behind the subtraction and reduces and reduced measuring accuracy.In order to guarantee the precision of testing result, just must get the AD converter of seniority, this will cause the device price to rise significantly again.In order to guarantee that measurement result has enough precision, used device price not too high again, and with the interval between two sampling values get big after, contradict with the basic demand of differentiating again.Solve this contradiction following way is arranged: get two minizones at the initial stage that temperature rise curve rises, on each minizone, get four, five sampled points.Make the curve fitting of this minizone of cubic spline function.Smooth because of the matched curve that cubic spline function is made, continuously and continuous single order and second order derived function arranged at the check point place.Can calculate stand-by T at the check point place ₁', T ₂' value.Depositing the difference quotient value of temperature value and temperature in RAM respectively at twice is: T ₁, T ₁' and T ₂, T ₂', use (A) formula can calculate warm T eventually again _S=T _{T → ∞}The method of cubic spline function interpolation calculation can find in the book of many explanation numerical evaluation, has in books of some explanation single-chip microcomputers to find the calculation procedure of having finished.

Have the machine such as the 80c196BK of 10 bit A/D converters and multichannel input in the sheet with 8 single-chip microcomputers as 96 series arbitrary, or the having 10 bit A/D converters in the sheet, multichannel input and the machine of EEPROM in the sheet is arranged such as AT90SMEG103 etc. can calculate temperature value according to formula (A) of AVR single-chip microcomputer.The single-chip microcomputer of these types all has the ready-made operational orders such as multiplication and division that add, subtract, and these computings all are the very familiar work of people, omit going through process flow diagram at this.

Because calculated amount is little, single-chip microcomputer can be competent at this simple evaluation work fully.And the single-chip microcomputer stable performance, cheap, peripheral circuit is simple, reliable, be easy to carry.These excellent conditions help the popularization on a large scale of this thermometer.

Claims (3)

1, a kind of fast prediction thermometer based on new temperature measuring principle, contain an instrumentation amplifier that temperature drift, zero point drift and time drift are all very little, with a single-chip microcomputer of calculating depths, determinand surface temperature computation program according to 2 temperature on the temperature rise curve and corresponding derivative value that contains the multi-channel A converter and derive according to heat-conduction equation

2, the fast prediction thermometer based on new temperature measuring principle according to claim 1, it is characterized in that, single-chip microcomputer has used can be from heat-conduction equation, according to comprised two temperature values and the corresponding single order derived function value on the temperature rise curve of various thermal parameters in the heat transfer system, the formula that foundation derives from heat-conduction equation: $T_s=\frac{T_1^{\&prime;}}{T_1^{\&prime;}-T_2^{\&prime;}}(T_2-T_1),$ Thereby the outer fast calculation procedure of extrapolating temperature probe temperature value of depths, determinand surface when the time of diabatic process is tending towards infinity,

3, the fast prediction thermometer based on new temperature measuring principle according to claim 1, it is characterized in that, a derivative value of directly not calculating temperature from the detected value of temperature with numerical differentiation is arranged, and with having the curve fitting of doing the minizone by check point and three rank splines method of interpolation with continuous single order derived function and second order derived function, thereby calculate derivative value, to increase the measuring accuracy of Temperature numerical with many significant figure.

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