CN102589743A - Digital display temperature detection system and digital display temperature detection method - Google Patents

Abstract

The invention relates to a high-resolution, wide-measurement range and low-cost digital display temperature detection system and a digital display temperature detection method. The digital display temperature detection system consists of a sensor probe, an analogue voltage signal acquisition circuit, an instrumentation amplifier, an analogue/digital converter, a processor, a drive chip and a digital display. The digital display temperature detection method comprises the following steps of: calling a signal acquisition module to perform voltage value sampling; calling an extreme value eliminating, filtering and averaging module to solve an average value; calling a table searching and temperature value converting module to convert the voltage value into a temperature value; calling a temperature value numerical system conversion module to convert a binary temperature value into a decimal temperature value; and calling a scanning drive module to perform dynamic scanning display. By the system and the method, the resolution of 0.1 DEG C and the measurement range of -15 to +80 DEG C are realized; and the problem that the conventional temperature gauge difficultly balances high resolution, wide measurement range and low cost is solved.

Description

Digital displays temperature detection system and digital displays temperature detection method

Technical field

The present invention relates to digital thermometry field, is a kind of high resolving power, wide measurement range, digital displays temperature detection system and digital displays temperature detection method cheaply.

Background technology

In industrial and agricultural production, national defence and scientific research field, digital displays temperature detection system relies on its advantage such as accurate, directly perceived that important use is arranged.Generally will utilize the probe of temperature sensor as temperature detection in the design of digital displays temperature detection system, temperature sensor can convert variation of temperature into the variation of the electric weight (like resistance, electromotive force etc.) that can measure.The design of digital displays temperature detection system generally is that temperature sensor is inserted in the testing circuit; From testing circuit, collect the analog voltage signal that changes with temperature variation then; Analog voltage signal sends A/D converter to through after the amplifier gain; A/D converter converts analog voltage signal to corresponding digital voltage signal, and sends it to microprocessor, and microprocessor is converted into corresponding temperature value; And control nixie display and carry out the number demonstration, show detected temperature value.

Based on the difference of application scenario, digital displays temperature detection system has different resolution ratio, precision and temperature-measuring range requirement, can adopt different types of temperature sensor as probe.Digital displays temperature detection system temperature sensor on related patent U.S. Patent No. and the market generally adopts thermopair, RTD or thermistor.Thermopair is the thermoelectric transducer that a kind of electromotive force changes with variation of temperature, and it is simple in structure, and temperature measurement range is wide, but thermopair pyrometry commonly used reaches 1600 ℃, and low temperature reaches-50 ℃, but its resolution is lower, generally more than 1 ℃; Platinum resistance temperature sensor is a kind of thermal resistance sensor commonly used, the temperature measurement range broad, but platinum resistance temperature sensor pyrometry commonly used reaches 850 ℃, and low temperature reaches-250 ℃; And have the advantage of precision height, good stability, but its temperature-coefficient of electrical resistance is smaller, in high-temperature reductibility atmosphere, uses; Contaminated easily, the usability variation produces after the fragility; Temperature-coefficient of electrical resistance is changed, thereby produce measuring error, and alloy platinum material costs an arm and a leg; The NTC thermistor is the temperature sensor that adopts ceramic process to process; Resistance is index law with the rising of temperature and reduces; Compare with other temperature sensors; NTC thermistor resolution is high, volume is little, response is fast, precision is high, stable performance, particularly in-50～+ 300 ℃ of scopes, is widely used.

The system for detecting temperature of high resolving power, wide measurement range is except having the higher requirement temperature sensor, and also hardware resource and the utilization ratio thereof to system has higher requirement.The multiword of seniority and microprocessor that the requirement of system hardware resources is mainly reflected in A/D converter is long, and this can improve the cost of system naturally; The raising of the utilization ratio of system hardware resources generally realizes through the linearization process to the variation relation of analog voltage signal and temperature value; And linearization process can only be similar to effectively within the specific limits; If in wider temperature range, carry out linearization process; Then need measurement range be divided into multistage, in each section, carry out linearization process respectively, when temperature survey, utilize switch to switch.For example; " accurate digital display compensation by thermistor " (Chinese patent of standard metering school design in Hebei province; Application number is 87214459) in; The NTC thermistor (temperature) sensor is connected in the Wheatstone bridge; In different temperature-measuring ranges, form Wheatstone bridge, utilize bridge output voltage in the opposite direction to the non-linear concavo-convex characteristic of temperature, the divider resistance R of suitable selection and the same brachium pontis of NTC thermistor the non-linear of NTC thermistor resistance and NTC thermistor resistance with 3 constant resistance of resistance ₂Value, make bridge output voltage be approximated to linear relationship, divider resistance R to temperature ₂The selection formula be:

${\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA0000143558490000021.png,HDA0000143558490000031.png"\; state="\{\{state\}\}">R</figure-callout>}}_2=\frac{R_{T1}{\mathrm{<figure-callout\; id="2"\; label="R\; T"\; filenames="HDA0000143558490000021.png,HDA0000143558490000031.png"\; state="\{\{state\}\}">R</figure-callout>}}_T+R_{T2}{R}_{T3}-2R_{T1}{R}_{T3}}{R_{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="HDA0000143558490000031.png,HDA0000143558490000091.png"\; state="\{\{state\}\}">T</figure-callout>}1}+R_{T3}-2R_{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000143558490000021.png,HDA0000143558490000031.png"\; state="\{\{state\}\}">T</figure-callout>}2}}$

In the formula, T1, T2 and T3 are respectively start-point temperature, neutral temperature and the end point temperature of a certain temperature-measuring range, R _T1, R _T2And R _T3Be respectively the resistance value of NTC thermistor under T1, T2 and T3 temperature.But linearization scope and linearization effect are mutual contradiction, and the linearization scope is wide more; Nonlinearity erron is big more; So standard metering school in Hebei province's is divided into 4 sections with temperature-measuring range in design, each section selected suitable divider resistance R according to above-mentioned formula respectively ₂, and switch with synchronous change-over switch.This linearization process in relative broad range makes circuit structure become comparatively complicated, if be not harshness very to the requirement of resolution and measurement range, for example; Requiring resolution is 0.1 ℃; Measurement range is-15～+ 80 ℃, and the temperature value that comprises is 951, and 8 A/D converters only comprise 2 ⁸=256 temperature values obviously can not meet the demands, and system can only select 12 or the A/D converter of seniority more for use, and 12 A/D converter comprises 2 ¹²=4096 temperature values; 951 temperature values far more than the needs detection; In this case, if design appropriate signal Acquisition Circuit, even the circuit linearization process would be carried out in not segmentation; Also can satisfy the use needs fully, this can make circuit structure obtain simplifying than the circuit linearization process.Under the requirement of above-mentioned resolution and measurement range, the single-chip microcomputer that can select 8 word lengths for use is as microprocessor, and its single-chip microcomputer than 16 word lengths or higher word length can reduce system cost.But; The single-chip microcomputer that utilizes 8 word lengths to 12 digital voltage signal receive, handle, operations such as the conversion from the magnitude of voltage to the temperature value, the numerical value conversion of temperature value difficulty relatively; The finite capacity of SCM program storer ROM particularly is when using look-up table to carry out the conversion from the magnitude of voltage to the temperature value, if deposit the magnitude of voltage and the temperature value of correspondence with it in program memory ROM simultaneously; Resolution and measurement range that to a great extent can restriction system; This just requires to design new tabling look-up and the temperature value transfer algorithm, both can accurately realize the conversion from the magnitude of voltage to the temperature value, can save taking program memory ROM again; Thereby improve the resolution of system, enlarge measurement range; Being stored in temperature value in two storage unit (most-significant byte and least-significant byte) for needs carries out also need designing new algorithm from scale-of-two to metric conversion and realizes.

What also have much room for improvement is; The NTC thermistor material that existing digital displays temperature detection system adopts mostly be by the oxide of elements such as high-purity transient metal Mn, Cu, Ni in co-precipitation powder process, isostatic compaction after 1200～1400 ℃ high temperature sintering form; High temperature sintering can improve the complicacy of NTC thermistor material technology of preparing, thereby has improved production cost of products; And the high precision NTC thermistor (temperature) sensor significant proportion of using in the existing product relies on import.Therefore be necessary in the design of digital displays temperature detection system, to select for use China to adopt the high precision NTC thermistor (temperature) sensor that designs and utilize the preparation of low-temperature sintering new technology voluntarily; To reduce cost of products; And in long-term application, check the performance of the NTC thermistor (temperature) sensor of designing and preparing voluntarily, further improve its mentality of designing and preparation technology.

Summary of the invention

The digital displays temperature detection system that the objective of the invention is to solve existing employing NTC thermistor (temperature) sensor is difficult to take into account the requirement of high resolving power, wide region temperature detection and expensive problem, for to the requirement of resolution and measurement range very the application of harshness a kind of digital displays temperature detection system and digital displays temperature detection method are provided.

Technical scheme of the present invention is: a kind of digital displays temperature detection system; By negative temperature coefficient (NTC) thermistor (temperature) sensor probe (1), analog voltage signal Acquisition Circuit (2), instrumentation amplifier (3), A/D converter (4), microprocessor (5), chip for driving (6); Nixie display (7) connects to form successively

A. analog voltage signal Acquisition Circuit (2) adopts Wheatstone bridge simple in structure, by NTC thermistor R _tWith 3 resistance value perseverances be R ₀Resistance as the brachium pontis of electric bridge, R _tOne end ground connection, the diagonal angle termination DC voltage U of ground connection ₀, R _tThe other end is high-voltage output terminal U ₊, U ₊The diagonal angle end be low-voltage output terminal U _-, the voltage stabilizing sheet is that electric bridge provides DC voltage U ₀, the analog voltage signal of electric bridge two ends output is to import the analog voltage signal U that instrumentation amplifier (3) gains _In=U ₊-U _-

B. instrumentation amplifier (3) is by instrumentation amplifier integrated circuit and feedback resistance R _GForm, the size of gain is by feedback resistance R _GValue regulate;

C. microprocessor (5) adopts the single-chip microcomputer of 8 word lengths, receives and handle the digital voltage signal of 12 A/D converter (4) transmission;

D. chip for driving (6) is made up of 14 Darlington pipes, under the control of microprocessor (5), drives nixie display (7), carries out dynamic scan and shows.

NTC thermistor temperature sensor probe (1) is inserted analog voltage signal Acquisition Circuit (2) as brachium pontis; The analog voltage signal of electric bridge output sends 12 A/D converter (4) to after gaining through instrumentation amplifier (3); Digital signal after A/D converter will be changed is again passed to the singlechip microprocessor (5) of 8 word lengths; The singlechip microprocessor of 8 word lengths is handled 12 digital signal; Convert magnitude of voltage into corresponding temperature value, controlling and driving chip (6) drives nixie display (7) and carries out the dynamic scan demonstration then; Adopt two transformers and corresponding rectification and filtering circuit constitute power panel come for system board provide+15 volts ,-15 volts and+5 volts voltage.

The present invention is according to the resistance R of the bridge resistor in systemic resolution and measurement range and the analog voltage signal Acquisition Circuit (2) ₀, bridge voltage U ₀Set up circuit parameter R with the analytic relationship of the gain G of instrumentation amplifier in the analog voltage signal gain circuitry (3) ₀, U ₀With the criterion of choosing of G, at first, should confirm R ₀Value because only satisfying R ₀＜R _tCondition under, the magnitude of voltage U of the high voltage end of electric bridge output ₊Magnitude of voltage U greater than low-voltage end _-, the value of the analog voltage signal of input A/D converter is for just, again because improve R ₀Value improving the resolution of system

The time can enlarge the measurement range of temperature, so should improve resistance R as far as possible ₀Value, make R ₀As far as possible near R _tMinimum value, i.e. the corresponding resistance value of maximum temperature; Next, confirm bridge voltage value U ₀Product GU with the instrumentation amplifier gain G ₀Value owing to improve U ₀Product GU with G ₀Can improve the resolution of digital displays temperature detection system

But under the certain situation of the aanalogvoltage input range that A/D converter requires, also can reduce the measurement range of temperature, so U ₀Product GU with G ₀Confirm to be divided into resolution

Preferentially guarantee preferentially to guarantee two kinds of situation, if resolution is preferentially guaranteed the R that at first will confirm with measurement range ₀Value, minimum temperature value T that expection detects and the resistance R of its corresponding NTC thermistor _tSubstitution resolution expression formula By the resolution that will guarantee

Try to achieve U ₀Product GU with G ₀Span and therefrom choose value less and that realize easily, then, with the R that has confirmed ₀Value, GU ₀Value and the resistance R of the minimum temperature value T corresponding N TC thermistor that detects with expection _tThe maximum analog voltage expression formula of max substitution instrumentation amplifier output

If U in the formula _OutThe value of max is not more than A/D converter and requires the highest analog voltage imported, and then the minimum temperature value T that detects of explanation expection can realize, and can sound out by above-mentioned steps and choose littler lowest detection temperature value, otherwise, if U in the formula _OutThe value of max is greater than the highest analog voltage of A/D converter requirement input, and then the minimum temperature value T of explanation expection detection cannot realize, should choose bigger lowest detection temperature value by the above-mentioned steps exploration, confirms GU again ₀Value; If measurement range is preferentially guaranteed, the R that at first will confirm ₀Value and the resistance R of the minimum temperature value T corresponding N TC thermistor that detects with expection _tThe maximum analog voltage expression formula of max substitution instrumentation amplifier output

Make U _OutMax is not more than the highest analog voltage of A/D converter requirement input, thereby tries to achieve U ₀Product GU with G ₀Span, and therefrom choose value bigger and that realize easily, the R that next will confirm ₀Value, GU ₀Value, minimum temperature value T that expection detects and the resistance R of its corresponding NTC thermistor _tSubstitution resolution expression formula

Try to achieve resolution Thereby try to achieve the temperature step-length of detection, promptly the voltage step size of A/D converter/ At last, according to side circuit and system works performance demands, distribute U ₀With G value separately.

Temperature sensor probe among the present invention is the chip NTC thermistor that designs and adopt the preparation of low-temperature sintering new technology voluntarily; Be fixed in the brass shell with epoxy resin; Process the sensor probe of temperature detection; This is the sensor probe of a kind of low-power consumption preparation, high-precision temperature detection with low cost, and the error of temperature coefficient B value is less than 3% in-15～+ 80 ℃ of temperature ranges.

With the corresponding digital displays temperature detection method of digital displays temperature detection system; By signals collecting touch piece, go extreme value filtering average module, table look-up and temperature value modular converter, temperature value numeral system modular converter, turntable driving module and form module are formed, it comprises the steps:

At first, piece is touched in 6 call signal collections, control A/D converter (4), and 6 analog voltage signals of continuous acquisition, and change into digital signal, send microprocessor (5) to; Call the extreme value filtering module of averaging then, with 6 digital voltage signals gathering with the ordering of bubbling method, remove maximal value and minimum value after, more remaining 4 groups of digital voltage signals are added up afterwards divided by 4, thereby try to achieve average voltage, be i.e. sample mean; If sample mean surpasses the scope of magnitude of voltage in the form, then make the F0 zero clearing of microprocessor (5), directly call the turntable driving module and carry out alarm indication; If sample mean is no more than the scope of magnitude of voltage in the form; Then make the F0 set of microprocessor (5); Call and table look-up and the temperature value modular converter; The order of each magnitude of voltage in sample mean and the form module being pressed from big to small (analog voltage signal of collection reduces with the rising of temperature, so corresponding temperature value is from low to high) compares, till the magnitude of voltage that finds correspondence or vicinity; At this moment the number of times that compares is exactly the magnitude of voltage of correspondence or arest neighbors to the relative address of the digital voltage value of maximum (be minimum temperature value-15 ℃); Be the sample relative address, then the sample relative address be converted into the relative address of sample mean with respect to 0 ℃ of corresponding voltage value, this relative address is exactly the absolute value of detected temperature value; Next call temperature value numerical value modular converter; To be converted into corresponding three (tenths behind ten, individual position and the radix point) decimal system numerical value with the temperature value of binary storage; Be converted into corresponding reveal codes again, and be stored in respectively in three storage unit of random data memory RAM of microprocessor (5); Call the turntable driving module at last, controlling and driving chip (6) sends the shows signal of nixie display (7) position choosing end and stroke end to, shows thereby carry out dynamic scan.

Table look-up and the temperature value modular converter is in the program memory ROM of single-chip microcomputer; Only deposit in-15～+ 80 ℃ of temperature ranges; With 0.1 ℃ is the pairing magnitude of voltage of each temperature value at interval; And do not deposit corresponding temperature value in, table look-up that what obtain is the corresponding relative address of sample mean, and then convert relative address into corresponding Temperature numerical.Its operation steps is following: (analog voltage signal of collection reduces with the rising of temperature by from big to small for will go extreme value filtering to average earlier sample mean that module tries to achieve and each magnitude of voltage in the form module; So corresponding temperature value is from low to high) order compare; Till the magnitude of voltage that finds correspondence or vicinity; At this moment the number of times that compares is exactly the magnitude of voltage of correspondence or arest neighbors with respect to the relative address of the magnitude of voltage of maximum (be minimum temperature value-15 ℃), i.e. sample relative address; Convert the sample relative address relative address of sample mean into then with respect to 0 ℃ of corresponding voltage value; (because systemic resolution is 0.1 ℃, so what obtain is 10 times of absolute value of temperature value) is about to the relative address comparison corresponding with 0 ℃ of sample relative address; If the sample relative address is more than or equal to the relative address of 0 ℃ of correspondence; Show that detected temperature value for just, then deducts the sample relative address relative address of 0 ℃ of correspondence, obtain 10 times of absolute value of positive temperature value; If the relative address of sample mean, shows detected temperature value less than 151 for negative, then the relative address with 0 ℃ of correspondence deducts the sample relative address, obtains 10 times of absolute value of negative temperature value.

Temperature value numeral system modular converter; Can will be stored in 951 possible temperature values utilize 8 word lengths in-15～+ 80 ℃ of scopes in two storage unit (most-significant byte and least-significant byte) single-chip microcomputer be three decimal system numerical value (are respectively ten, individual position and radix point after tenths) with it from Binary Conversion; And be stored in respectively in three registers, promptly register 4 is deposited ten value corresponding, and register 5 is deposited a position value corresponding; Register 6 is deposited the tenths value corresponding; What be worth explanation is, because resolution is 0.1 ℃, sample mean is ten times of actual temperature value with respect to the relative address of 0 ℃ of corresponding voltage value; So in transfer process; Be stored in numerical value that the whole tuber of stemona in the register 4 divides and be the numerical value on ten when showing, the numerical value that is stored in whole ten parts in the register 5 is the numerical value on the position when showing, the numerical value the when numerical value that is stored in a bit position in the register 6 is demonstration on the tenths.The operation steps of this module is following: at first register 1 is added in the register 4 divided by 100 integral parts that obtain and goes, from register 1, deduct then and be added to the numerical value that the whole tuber of stemona that goes in the register 4 divides, because positive temperature and negative temperature corresponding voltage value all are no more than 800 with respect to the relative address of 0 ℃ of corresponding voltage value; So the numerical value of most-significant byte register 2 storages only possibly be 1,2 or 3, if 1, show that the numerical values recited of most-significant byte register 2 storages is 256; Let the numerical value in the register 4 add 2, be added in the register 1 56 then and go, if 2; The numerical values recited that shows 2 storages of most-significant byte register is 512; Make the numerical value in the register 4 add 5, be added in the register 1 12 then and go, if 3; Show that it is 768 that most-significant byte is deposited the numerical values recited of 2 storages; Make the numerical value in the register 4 add 7, be added in the register 1 68 then and go, at this moment the numerical value in the register 1 may surpass 100; Go so again register 1 is added in the register 4 divided by 100 integral parts that obtain; From register 1, deduct then and be added to the numerical value that the whole tuber of stemona that goes in the register 4 divides, go up the numerical value that show for such ten and just be stored in the register 4, simultaneously all disallowable the going out of numerical value of whole tuber of stemona branch in register 1 and the register 2; Next; Register 1 stored in the register 5 divided by 10 integral parts that obtain go; And from register 1, deduct the numerical value that is added to whole ten parts of going in the register 5; The numerical value that should show on the position so just is stored in the register 5, simultaneously disallowable the going out of numerical value of whole ten parts in the register 1; Next, what register 1 was stored is the numerical value of a bit position, is stored in the register 6 and goes, and the numerical value that should show on the tenths so just is stored in the register 6; So just accomplished temperature value by scale-of-two to metric conversion.

The invention provides and a kind ofly can take into account high resolving power, wide measurement range and novel digital displays temperature detection system and corresponding digital displays temperature detection method cheaply.On the one hand through selecting Wheatstone bridge simple in structure Acquisition Circuit for use, and according to the resistance R in systemic resolution and measurement range and the electric bridge as analog voltage signal ₀, electric bridge DC voltage U ₀Set up circuit parameter R with the analytic relationship of the gain G of instrumentation amplifier ₀, U ₀With the criterion of choosing of G, thereby choosing of circuit parameter is optimized; Handle 12 digital signal on the other hand through the singlechip microprocessor of selecting 8 word lengths for use, and new table look-up and temperature value transfer algorithm and temperature value numeral system transfer algorithm make the utilization ratio raising of the hardware resource of system that combines design voluntarily; This two aspect makes the cost of system obtain reduction; And realized 0.1 ℃ resolution;-15～+ 80 ℃ measurement range has solved at the very harsh existing thermometer of application of the requirement of resolution and measurement range and has been difficult to take into account high resolving power, wide measurement range and problem cheaply.Simultaneously; The present invention has used the NTC thermistor temperature sensor that designs and utilize the high-precision low cost of low-temperature sintering new technology preparation voluntarily; This is to check the performance of the NTC thermistor (temperature) sensor of designing and preparing voluntarily, further improves its mentality of designing and preparation technology possibility is provided.

Description of drawings

Fig. 1 (a) is digital displays temperature detection system block diagram;

Fig. 1 (b) is digital displays temperature detection system bridge diagram schematic diagram;

Fig. 2 is instrumentation amplifier output voltage and systemic resolution and temperature variation relation curve;

Fig. 3 (a) is digital displays temperature detection system power panel circuit theory diagrams;

Fig. 3 (b) is digital displays temperature detection system system board circuit theory diagrams;

Fig. 4 is digital displays temperature detection method process flow diagram;

Fig. 5 is that signals collecting is touched the piece process flow diagram;

Fig. 6 is the extreme value filtering module process flow diagram of averaging;

Fig. 7 tables look-up and temperature value modular converter process flow diagram;

Fig. 8 is a temperature value numeral system modular converter process flow diagram;

Fig. 9 is a turntable driving module process flow diagram.

Embodiment

Embodiment one

Present embodiment is the realization of digital displays temperature detection system.

Digital displays temperature detection system is shown in Fig. 1 (a); The NTC thermistor that adopts the low temperature sintering technology preparation is as temperature sensor probe; Be fixed in the brass shell with epoxy resin, process the probe of temperature detection, the NTC thermistor is processed sensor probe (1) and the permanent R of being of 3 resistances ₀Resistance R ₁, R ₂And R ₃Couple together; Form Wheatstone bridge, as analog voltage signal Acquisition Circuit (2), shown in Fig. 1 (b); The analog voltage signal of gathering sends 12 the A/D converter AD1674 (4) that compares type fast one by one to after gaining through instrumentation amplifier AD620 (3); Digital signal after A/D converter AD1674 (4) will change is again passed to the AT89C51 singlechip microprocessor (5) of 8 word lengths, and microprocessor (5) is handled 12 digital signal, converts magnitude of voltage into corresponding temperature value; Control ULN2004 chip for driving (6) then; Drive 4 altogether anode light diode display (7) carry out dynamic scan and show, shown in Fig. 3 (b), adopt the transformer of two 220V/20V and corresponding rectification and filtering circuit to constitute power panel; Shown in Fig. 3 (a), for digital displays temperature detection system mainboard provide+15 volts ,-15 volts and+5 volts reference voltage and WV.

The present invention is according to the electric bridge reference arm resistance R in systemic resolution and measurement range and the analog voltage signal Acquisition Circuit (2) ₀, bridge voltage U ₀Set up circuit parameter R with the analytic relationship of the gain G of instrumentation amplifier in the analog voltage signal gain circuitry (3) ₀, U ₀With the criterion of choosing of G, come the selecting circuit parameters R according to this criterion ₀, U ₀Can make system satisfy resolution and measurement range that expection requires with G, the serviceability of system is optimized.Circuit parameter R ₀, U ₀With G choose criterion to set up process following: by NTC thermistor R _tWith 3 resistance values be R ₀Resistance form Wheatstone bridge as brachium pontis, R _tOne end ground connection, the diagonal angle termination DC voltage U of ground connection ₀, R _tThe other end is high-voltage output terminal U ₊, U ₊The diagonal angle end be low-voltage output terminal U _-, the voltage stabilizing sheet is that electric bridge provides DC voltage U ₀, the analog voltage signal of electric bridge two ends output is to import the analog voltage signal U that instrumentation amplifier gains _In:

$U_{\mathrm{in}}=U_{+}-U_{-}=(\frac{1}{2}-\frac{R_0}{R_t+R_0})U_0---\left(1\right)$

For the analog voltage signal that guarantees the input instrumentation amplifier for just, get R here ₀＜R _tThe analog voltage signal U of instrumentation amplifier gain back output _OutFor:

$U_{\mathrm{out}}={\mathrm{GU}}_{\mathrm{in}}={\mathrm{GU}}_0(\frac{1}{2}-\frac{R_0}{R_t+R_0})---\left(2\right)$

NTC thermistor R _tResistance value with the relation that temperature T changes be:

$R_t=A_0\exp \left[B(\frac{1}{T}-\frac{1}{T_0})\right]=\mathrm{Aexp}\left(\frac{B}{T}\right)---\left(3\right)$

Wherein: $A=A_0\mathrm{Exp}(-\frac{B}{T_0})$

T ₀: a certain temperature value;

A ₀: T ₀Resistance value under the temperature;

B: the material temperature constant of thermistor, experiment is measured as 3454K, and error is less than 3%; Negative tempperature coefficient thermistor R _tRising with temperature T reduces by index law, and the analog voltage U that gathers _OutRising with temperature T reduces, and is as shown in Figure 2.Analog voltage signal U _OutWith negative tempperature coefficient thermistor R _tChanging Pattern be:

$\frac{{\mathrm{dU}}_{\mathrm{out}}}{d{R}_t}=\frac{{\mathrm{GU}}_0{R}_0}{{(R_t+R_0)}^2}---\left(4\right)$

Resolution by can draw digital displays temperature detection system with following formula (3) and (4) is:

$\left|\frac{{\mathrm{dU}}_{\mathrm{out}}}{\mathrm{dT}}\right|=-\frac{{\mathrm{dU}}_{\mathrm{out}}}{\mathrm{dT}}=-\frac{d{U}_{\mathrm{out}}}{{\mathrm{dR}}_t}\frac{d{R}_t}{\mathrm{dT}}=\frac{{\mathrm{BGU}}_0{R}_0{R}_t}{T^2{(R_t+R_0)}^2}---\left(5\right)$

According to (2) formula, (be R necessarily in temperature measurement range _tVariation range certain) situation under, analog voltage U _OutMaximal value be:

$U_{\mathrm{out}}\max ={\mathrm{GU}}_0(\frac{1}{2}-\frac{R_0}{R_t\max +R_0})---\left(6\right)$

First step analytic system resolution

With the maximum analog voltage U _OutMax is with circuit parameter R ₀, U ₀Variation relation with G.Visible by formula (5), systemic resolution Be decided by

With

Product, Be the characteristic of NTC thermistor own, improve resolution

Approach be to select suitable circuit parameter to improve Can find out by formula (4), on the one hand

With the product GU of instrumentation amplifier gain with the bridge voltage value ₀Linear, improve GU ₀Value can improve Thereby raising resolution

On the other hand

With R ₀Variation relation be:

$\frac{\&PartialD;}{\&PartialD;R_0}\left(\frac{{\mathrm{dU}}_{\mathrm{out}}}{d{R}_t}\right)=\frac{{\mathrm{GU}}_0(R_t+R_0)(R_t-R_0)}{{(R_t+R_0)}^4}>0---\left(7\right)$

Thus it is clear that, improve R ₀Also can improve Thereby raising resolution

Can find out from above analysis, improve the product GU of instrumentation amplifier gain and bridge voltage value ₀And R ₀All can improve the resolution of system

Can find out by formula (6), on the one hand U _OutThe product GU of max and instrumentation amplifier gain and bridge voltage value ₀Linear, improve GU ₀Value can make U _OutMax increases, and this can reduce the measurement range of temperature under the certain situation of the aanalogvoltage input range of A/D converter requirement; U on the other hand _OutMax is with R ₀Variation relation be:

$\frac{{\&PartialD;U}_{\mathrm{out}}\max }{\&PartialD;{\mathrm{<figure-callout\; id="0"\; label="R"\; filenames="HDA0000143558490000021.png,HDA0000143558490000031.png"\; state="\{\{state\}\}">R</figure-callout>}}_0}=-{\mathrm{GU}}_0\frac{R_t\max }{{(R_t\max +R_0)}^2}<0---\left(8\right)$

Thus it is clear that, improve R ₀Value can make U _OutMax reduces, thereby enlarges the measurement range of temperature.

Can find out from above analysis, improve the product GU of instrumentation amplifier gain and bridge voltage value ₀Value can dwindle the measurement range of temperature, and improve R ₀Value can enlarge the measurement range of temperature.

Comprehensive above analysis can be found out, improves the product GU of instrumentation amplifier gain and bridge voltage value ₀Can improve the resolution of digital displays temperature detection system

But under the certain situation of the aanalogvoltage input range that A/D converter requires, also can reduce the measurement range of temperature; And raising R ₀Value improving the resolution of system

The time can enlarge the measurement range of temperature; For the analog voltage signal that guarantees the input instrumentation amplifier for just, R ₀Value can not be greater than R _tSo improving resolution is these those length that disappear with enlarging measurement range, mutual restriction, its equilibrium point must be selected according to actual needs.

Second step is at circuit parameter R ₀, U ₀With analytic system resolution under the definite situation of G

With aanalogvoltage variation range delta U _OutVariation relation with temperature T.The resolution of digital displays temperature detection system with variation of temperature is:

$\frac{d}{\mathrm{dT}}\left(\right|\frac{{\mathrm{dU}}_{\mathrm{out}}}{\mathrm{dT}}\left|\right)=-\frac{d^2{U}_{\mathrm{out}}}{{\mathrm{<figure-callout\; id="2"\; label="dT"\; filenames="HDA0000143558490000021.png,HDA0000143558490000031.png"\; state="\{\{state\}\}">dT</figure-callout>}}^2}=\frac{{\mathrm{BGU}}_0{R}_0{R}_t}{{(R_t+R_0)}^3{T}^4}[B(R_t-R_0)-2T(R_t+R_0)]---\left(9\right)$

When

$R_t=\frac{R_0(B+2T)}{B-2T}---\left(10\right)$

The time,

Because improve R ₀Value improving the resolution of system

The time can enlarge the measurement range of temperature, so should improve resistance R as far as possible ₀Value, make R ₀As far as possible near R _tMinimum value, NTC thermistor R _tMinimum resistance in working range (being the resistance value of 80 ℃ of correspondences of highest detection temperature) is 1.94k Ω, gets R here ₀=1.8k Ω, the numerical solution of trying to achieve equation shown in the formula (10) is T=342K=69 ℃, when T＜69 ℃,

Resolution

Rising with temperature improves, and when T＞69 ℃,

Resolution Continuation rising with temperature reduces, so in the time of T=69 ℃, resolution

Obtain maximal value, can know according to formula (5) again, the resolution of the resolution in the time of T=80 ℃ during greater than T=-15 ℃ is so the resolution of digital displays temperature detection system obtains minimum in low-temperature end.If realize 0.1 ℃ resolution, then require at 0.1 ℃ of low-temperature end temperature variation, analog voltage signal U _OutVariation greater than the step-length of A/D converter.

Show analog voltage signal U _OutRising with temperature T reduces, this explanation low-temperature end corresponding simulating voltage signal U _OutGreatly, minimum temperature is corresponding to the maximal value U of analog voltage signal _OutMax, circuit parameter R ₀, U ₀Actual to the restriction of systematic survey scope with G is restriction to minimum measurement temperature, the maximal value U of analog voltage signal _OutMax should be less than the highest analog input voltage of A/D converter requirement.

More than the analysis of two aspects can know minimum resolution and maximum analog voltage signal U _OutMax all obtains in low-temperature end, so the definite of circuit parameter should be determined by low-temperature end.

So, circuit parameter R ₀, U ₀With G should be definite like this: at first, should confirm R ₀Value because only satisfying R ₀＜R _tCondition under, the magnitude of voltage U of the high voltage end of electric bridge output ₊Magnitude of voltage U greater than low-voltage end _-, the value of the analog voltage signal of input A/D converter is for just, again because improve R ₀Value improving the resolution of system

The time can enlarge the measurement range of temperature, so should improve resistance R as far as possible ₀Value, make R ₀As far as possible near R _tMinimum value, i.e. the corresponding resistance value of maximum temperature.Next, confirm bridge voltage value U ₀Product GU with the instrumentation amplifier gain G ₀Value owing to improve U ₀Product GU with G ₀Can improve the resolution of digital displays temperature detection system

But under the certain situation of the aanalogvoltage input range that A/D converter requires, also can reduce the measurement range of temperature, so U ₀Product GU with G ₀Confirm to be divided into resolution

Preferentially guarantee preferentially to guarantee two kinds of situation, if resolution is preferentially guaranteed the R that at first will confirm with measurement range ₀Value, minimum temperature value T that expection detects and the resistance R of its corresponding NTC thermistor _tSubstitution (5) formula is by the resolution that will guarantee

Try to achieve U ₀Product GU with G ₀Span and therefrom choose value less and that realize easily, then, with the R that has confirmed ₀Value, GU ₀Value and the resistance R of the minimum temperature value T corresponding N TC thermistor that detects with expection _tMax substitution (6) formula is U in (if 6) formula _OutThe value of max is not more than A/D converter and requires the highest analog voltage imported, and then the minimum temperature value T that detects of explanation expection can realize, and can sound out by above-mentioned steps and choose littler lowest detection temperature value, otherwise, if U in (6) formula _OutThe value of max is greater than the highest analog voltage of A/D converter requirement input, and then the minimum temperature value T of explanation expection detection cannot realize, should choose bigger lowest detection temperature value by the above-mentioned steps exploration, confirms GU again ₀Value; If measurement range is preferentially guaranteed, the R that at first will confirm ₀Value and the resistance R of the minimum temperature value T corresponding N TC thermistor that detects with expection _tMax substitution (6) formula makes U _OutMax is not more than the highest analog voltage of A/D converter requirement input, thereby tries to achieve U ₀Product GU with G ₀Span, and therefrom choose value bigger and that realize easily, the R that next will confirm ₀Value, GU ₀Value, minimum temperature value T that expection detects and the resistance R of its corresponding NTC thermistor _tSubstitution (5) formula is tried to achieve resolution

Thereby try to achieve the temperature step-length of detection, promptly the voltage step size of A/D converter/

At last, according to side circuit and system works performance demands, the balanced U that distributes ₀With G value separately, because U ₀Crossing conference, to make resistance be R ₀The heating of three arm resistances, the drift that produces resistance, the precision that influence is measured, and the gain G of instrumentation amplifier is crossed conference and produced bigger noise, and signal to noise ratio (S/N ratio) is reduced.

Choose criterion and confirm R according to circuit parameter according to systemic resolution and measurement range ₀, U ₀Value with G.NTC thermistor (temperature) sensor probe provides in-15～+ 80 ℃ of temperature ranges; With 2.5 ℃ is the corresponding resistance value of each temperature value of step-length; Between per 2 temperature values, utilizing the method for linear interpolation to try to achieve in this temperature range, is the corresponding resistance value of each temperature value of step-length with expection resolution.Here, we at first example how to choose criterion according to circuit parameter, be selecting circuit parameters R under 0.1 ℃ the performance index situation about preferentially guaranteeing at systemic resolution ₀, U ₀And G.At first, NTC thermistor R _tMinimum resistance in working range (i.e. the resistance values of 80 ℃ of correspondences of maximum temperature value that expection detects) is 1.94k Ω, in order to improve resistance R as far as possible ₀Value, make R ₀As far as possible near R _tMinimum value, get R here ₀=1.8k Ω; Next, satisfy 0.1 ℃ resolution requirement, during T=-15 ℃ of the minimum temperature value that should detect in expection, make analog voltage signal U during 0.1 ℃ of temperature variation _OutVariation (here, we choose 12 A/D converter AD1674, and it requires analog voltage range of input is 0～10V or 0～20V, and we select the scope of 0～10V, and step-length is 10/ (2 so greater than the step-length of A/D converter ¹²-1) V), promptly

R in formula (5) _tExpect for the people and the resistance 71.7k Ω of the minimum temperature value-15 ℃ correspondence that detects to obtain GU ₀From then on＞19.7V chooses less and value GU that realize easily in the scope ₀=20.4; Then, with R ₀=1.8k Ω, GU ₀=20.4 and the resistance R of T=-15 ℃ of corresponding N TC of the minimum temperature value thermistor that detects with expection _tMax=71.7k Ω substitution (6) formula obtains U _OutMax=9.7V, the highest analog voltage 10V less than A/D converter AD1674 requires input explains that the minimum temperature value that expection detects can realize for T=-15 ℃; At last, consider side circuit and system works performance demands, distribute U ₀=+5V, G=4.08, the gain G of instrumentation amplifier AD620 and feedback resistance R _GRelation do

So R that G=4.08 is corresponding _G=16k Ω.

Next, how we example choose criterion according to circuit parameter, are selecting circuit parameters R under-15～+ 80 ℃ the performance index situation about preferentially guaranteeing in the systematic survey scope ₀, U ₀And G.At first, R _tMinimum value (i.e. the resistance values of 80 ℃ of correspondences of maximum temperature value that expection detects) be 1.94k Ω, in order to improve resistance R as far as possible ₀Value, make R ₀As far as possible near R _tMinimum value, get R here ₀=1.8k Ω; Next, with R ₀The resistance R of=1.8k Ω and T=-15 ℃ of corresponding N TC of the minimum temperature value thermistor that detects with expection _tMax=71.7k Ω substitution (6) formula makes U _OutMax is not more than the highest analog voltage 10V of A/D converter requirement input, thereby tries to achieve U ₀Product GU with G ₀Span GU ₀≤21.0, from then on choose bigger in the scope and value GU that realize easily ₀=20.4, then, with R ₀=1.8k Ω, GU ₀=20.4, T=-15 ℃ of the minimum temperature value of expection detection and the resistance R of its corresponding NTC thermistor _t=71.7k Ω substitution (5) formula is tried to achieve resolution Thereby try to achieve the temperature step-length of detection, promptly the voltage step size of A/D converter/

At last, consider side circuit and system works performance demands, distribute U ₀=+5V, G=4.08, the gain G of instrumentation amplifier AD620 and feedback resistance R _GRelation do

So R that G=4.08 is corresponding _G=16k Ω.

As shown in Figure 2, with the circuit parameter R that has confirmed ₀=1.8k Ω, U ₀The material temperature constant B=3454K of=+ 5V, G=4.08 and NTC thermistor parameter brings the aanalogvoltage expression formula (2) and the systemic resolution expression formula (5) of instrumentation amplifier output into, obtains aanalogvoltage U _OutAnd resolution

Change curve with temperature T.Thus it is clear that, aanalogvoltage U _OutRising with temperature T reduces, and obtains maximal value U at low-temperature end T=-15 ℃ _OutMax=9.7V; When T＜69 ℃, resolution

Rising with temperature improves, and when T＞69 ℃, resolution

Raise with the continuation of temperature and to reduce, the resolution of the resolution in the time of T=80 ℃ during, resolution greater than T=-15 ℃ Obtain minimum at low-temperature end T=-15 ℃.

Shown in accompanying drawing 3 (a), adopt the transformer T of two 220V/20V ₁And T ₂, transformer T ₁Output terminal 3 and 4 respectively with rectifier bridge B ₁Two sections of AC link to each other rectifier bridge B ₁V-end ground connection, the V+ end links to each other with the input end 1 of voltage stabilizing sheet 7805 and voltage stabilizing sheet 7815, the C of while and electric capacity 470 μ F ₆, C ₇And C ₉Link to each other capacitor C ₆, C ₇And C ₉Other end ground connection; The output terminal 3 of voltage stabilizing sheet 7815 and voltage stabilizing sheet 7805 provides+voltage of 15 volts and+5 volts for system, the capacitor C of while and 470 μ F ₈And C ₁₀Link to each other capacitor C ₈And C ₁₀Other end ground connection, port 2 ground connection of voltage stabilizing sheet 7815 and voltage stabilizing sheet 7805; Transformer T ₂Output terminal 4 and 5 respectively with rectifier bridge B ₂Two sections of AC link to each other rectifier bridge B ₁V+ end ground connection, the V-end links to each other with the input end 2 of voltage stabilizing sheet 7915, the capacitor C of while and 470 μ F ₁₁And C ₁₂Link to each other capacitor C ₁₁And C ₁₂Other end ground connection, the output terminal 3 of voltage stabilizing sheet 7915 provides-15 volts voltage for system, simultaneously with the capacitor C of 470 μ F ₁₃Link to each other capacitor C ₁₃Other end ground connection, the port one ground connection of voltage stabilizing sheet 7805.

Shown in accompanying drawing 3 (b), the input end of low power stabilized sheet 78L05 provides with power panel+5 volts link to each other, output terminal is that Wheatstone bridge provides+5 volts voltage, input end and output terminal simultaneously with the capacitor C of 30pF ₁And C ₂Connect capacitor C ₁And C ₂Other end ground connection; The high voltage end U of Wheatstone bridge output ₊With low-voltage end U _-Link to each other with simulation negative terminal-in simulation anode+in of instrumentation amplifier AD620 respectively, for instrumentation amplifier AD620 provides the aanalogvoltage input signal; Resistance is the feedback resistance R of 16k Ω _GTwo ends respectively with the R of instrumentation amplifier AD620 _GEnd connects, as the gain resistor of instrumentation amplifier; Instrumentation amplifier AD620+vs and-vs respectively with power panel provide+15 volts link to each other with-15 volts, the reference voltage of work is provided for instrumentation amplifier AD620; The analog voltage input 10V of the aanalogvoltage output terminal out of instrumentation amplifier AD620 and the 10V of A/D converter AD1674 _InLink to each other, for A/D converter AD1674 provides the aanalogvoltage input signal; The ref pin ground connection of instrumentation amplifier AD620 is for chip operation provides reference zero; The STS of A/D converter AD1674, CS, A ₀, R/C links to each other with P0.1, P0.2, P0.3, P0.4 and the P0.5 of AT89C51 single-chip microcomputer respectively with CE, is transmission control and request signal between AT89C51 single-chip microcomputer and the A/D converter AD1674, resistance is the resistance R of 0.1k Ω ₈～R ₁₂One end links to each other with P0.1, P0.2, P0.3, P0.4 and the P0.5 of AT89C51 single-chip microcomputer, and the other end links to each other with 5 volts power supply, as the pull-up resistor of P0 port; DB4～DB11 of A/D converter AD1674 links to each other with the P2.0～P2.7 of AT89C51 single-chip microcomputer; DB0～DB3 of A/D converter AD1674 links to each other with the P2.4～P2.7 of AT89C51 single-chip microcomputer, so that the digital voltage signal of A/D converter AD1674 after AT89C51 single-chip microcomputer output conversion; The 12/8 pin ground connection of A/D converter AD1674, when making the single-chip microcomputer reading, A/D converter is that byte is exported at twice; The V of A/D converter AD1674 _CcAnd V _EeRespectively with power panel provide+15 volts link to each other with-15 volts, the reference voltage of work is provided for A/D converter AD1674; The REFin of A/D converter AD1674 and REFout are by the adjustable resistance R of a 0.1k Ω ₄Link to each other, to provide the inner decoding network required reference voltage; The three end adjustable resistance R of 100k Ω ₅Two ends, outside and power panel provide+15 volts link to each other with-15 volts of voltages, the other end successively with the resistance R of 100k Ω ₆, 0.1k Ω R ₇Link to each other with reference ground, the BIPoff of A/D converter AD1674 is connected resistance R ₆And R ₇Between, be the zero point of A/D converter AD1674 adjustment ADC output; The simulation ground of A/D converter AD1674 is held AG and is digitally held DG all with reference to ground to link to each other; Vl links to each other with+5 volts of voltages, and AD1674 provides WV for A/D converter; The analog voltage input 20V of the 20V of AD1674 _InPin is unsettled; Each chip for driving ULN2004 is made up of 7 Darlington pipes; Utilize two ULN2004 that 14 Darlington pipes can be provided; P1.0～the P1.7 of AT89C51 single-chip microcomputer links to each other with the input end of wherein 8 Darlington pipe respectively, the output terminal that 8 Darlington manage respectively be connected the pull-up resistor R that resistance is 0.1k Ω ₁₄～R ₂₁(exclusion)+5 volts power supply links to each other; Also link to each other with 4 stroke end a～dp that are total to the anode light diode simultaneously; P3.0～the P3.5 of AT89C51 single-chip microcomputer links to each other with the input end of wherein 6 Darlington pipe respectively, the output terminal that 6 Darlington manage respectively be connected the pull-up resistor R that resistance is 0.1k Ω ₂₂～R ₂₇(exclusion)+5 volts power supply links to each other; Also simultaneously with 4 altogether the position choosing end 1～4 of anode light diode link to each other with red light emitting diodes Red and hummer Alarm; By AT89C51 Single-chip Controlling ULN2004 chip, 4 of reverse drive are total to the anode charactron and carry out dynamic scan demonstration or warning; The other end of red light emitting diodes and hummer is ground connection respectively; Green LED Green one end links to each other with+5 volts power supply, and other end ground connection begins luminous when system powers on; Crystal oscillator CRYSTAL two ends respectively with the capacitor C of 30pF ₃And C ₄Link to each other, also simultaneously link to each other capacitor C with XTAL2 with the XTAL1 of AT89C51 single-chip microcomputer ₃And C ₄Between ground connection, the clock signal of 12MHz is provided for the AT89C51 single-chip microcomputer; + 5 volts power supply connects the capacitor C 5 of 10pF, the resistance R of 10k Ω successively ₁₃, ground connection then, the RST of AT89C51 single-chip microcomputer is connected capacitor C ₅And resistance R ₁₃Between, the circuit that powers on of formation AT89C51 single-chip microcomputer, the Vcc of AT89C51 single-chip microcomputer links to each other with+5 volts of voltages, for single-chip microcomputer provides WV, Vss ground connection; The EA of T89C51 single-chip microcomputer links to each other with+5 volts of voltages, to use AT89C51 single-chip microcomputer sheet internal program storer ROM; Other pins of AT89C51 single-chip microcomputer are unsettled simultaneously.

After system powers on, start working, when temperature is in-15～+ 80 ℃ of scopes, the green luminous signal thermometer of light emitting diode Green operate as normal, resolution is 0.1 ℃; When temperature surpassed-15～+ 80 ℃ of scopes, red light emitting diode Red was luminous, cooperated the sound of hummer Alarm to report to the police.

Embodiment two

Present embodiment is the realization with the corresponding digital displays temperature detection method of digital displays temperature detection system.

Based on the digital displays temperature detection method of AT89C51 single-chip microcomputer, by signals collecting touch piece, go extreme value filtering average module, table look-up and temperature value modular converter, temperature value numeral system modular converter, turntable driving module and form module are formed.Shown in accompanying drawing 4, at first, piece is touched in 6 call signal collections, control A/D converter (4), and 6 analog voltage signals of continuous acquisition, and change into digital signal, send microprocessor (5) to; Call the extreme value filtering module of averaging then, with 6 digital voltage signals gathering with the ordering of bubbling method, remove maximal value and minimum value after, more remaining 4 groups of digital voltage signals are added up afterwards divided by 4, thereby try to achieve average voltage, be i.e. sample mean; If sample mean surpasses the scope of magnitude of voltage in the form, then directly call the turntable driving module and carry out alarm indication; If sample mean is no more than the scope of magnitude of voltage in the form; Then call and table look-up and the temperature value modular converter; With each magnitude of voltage in sample mean and the form module by (analog voltage signal of collection reduces with the rising of temperature from big to small; So corresponding temperature value is from low to high) order compare; Till finding correspondence or contiguous magnitude of voltage, the number of times that at this moment compares is exactly the magnitude of voltage of correspondence or arest neighbors to the relative address of the digital voltage value of maximum (be minimum temperature value-15 ℃), i.e. sample relative address; Then the sample relative address is converted into the relative address of sample mean with respect to 0 ℃ of corresponding voltage value, this relative address is exactly the absolute value of detected temperature value; Next call temperature value numeral system modular converter; To be converted into corresponding three (tenths behind ten, individual position and the radix point) decimal system numerical value with the temperature value of binary storage; Utilize form 2 (depositing 0 to 9 pairing reveal codes in the form 2 in) to be converted into corresponding reveal codes again; And be stored in respectively in three storage unit of random data memory RAM of microprocessor (5), call the turntable driving module at last, controlling and driving chip (6); Send the shows signal of nixie display (7) position choosing end and stroke end to, show thereby carry out dynamic scan.

Shown in accompanying drawing 5, it is that microprocessor (5) control A/D converter (4) is gathered analog voltage signal that signals collecting is touched piece, and converts it into digital signal, sends microprocessor (5) to.Its implementation detail is following: with STS, CS, the A of A/D converter AD1674 ₀, R/C links to each other with 5 I/O pins of AT89C51 single-chip microcomputer respectively with the CE pin, is transmission control and request signal between AT89C51 single-chip microcomputer and the A/D converter AD1674, wherein STS is the output state pin; During the conversion beginning, STS reaches high level, keeps high level in the transfer process; When converting, turn back to low level, wherein CS is the chip selection signal end; Low level is effective, wherein A ₀Be that byte is selected control line, in the transition period, A ₀=0, AD1674 carries out complete 12 conversions, between reading duration, and A ₀=0 o'clock, the most-significant byte data were effective, A ₀=1 o'clock, low 4 bit data were effective, and middle 4 is 0, and high 4 is ternary; Wherein R/C is read data/changeover control signal, and during R/C=1, the data of AD1674 transformation result allow to be read, when R/C=0; Permission starts the A/D conversion, and wherein CE starts the switching signal control end, and high level is effective, can be used as the enabling signal of A/D conversion startup or reading of data; DB4～DB11 of A/D converter AD1674 (most-significant byte signal) should link to each other with the Pi mouth (i=0,1,2,3) of AT89C51 single-chip microcomputer, and DB0～DB3 of A/D converter AD1674 (low 4 signals) links to each other with the Pi.4～Pi.7 of AT89C51 single-chip microcomputer, and each conversion is read at twice, reads most-significant byte earlier; Read low 4 again, before each reading, the AT89C51 single-chip microcomputer is received the port write 1 of data, to read correct signal; At first, with the CE zero clearing, again with A ₀Zero clearing is provided with 12 A/D conversions, subsequently with the R/C zero clearing, prepares 12 A/D conversions; CE puts 1, starts 12 A/D conversions, and the pin that links to each other with STS puts 1, to read correct signal; Inquiry is set,, 0FFH is composed to the Pi mouth to read correct signal, then data are read among the totalizer A if STS becomes low level; Subsequently data among the totalizer A are forwarded in the ram memory cell, then with the CE zero clearing, again with A ₀Put 1, be provided with and read low 4 position digital signals, CE puts 1, prepares to read low 4 position digital signals, and 0FFH is composed to the Pi mouth to read correct signal, then data is read among the totalizer A, subsequently data among the totalizer A is forwarded in the ram memory cell;

Shown in accompanying drawing 6, going the extreme value filtering module of averaging is that 6 digital voltage values gathering are sorted with the bubbling method, removes maximal value and minimum value; With the summation that adds up of four magnitudes of voltage in the middle of coming; Again divided by 4, thereby try to achieve average voltage level, i.e. sample mean.Its implementation detail is following: double-deck circulation at first is set, with register 1 as outer cycle counter, with register 2 as the interior loop counter; The magnitude of voltage that has 6 collections among the data-carrier store RAM altogether so outer circulation initial count is 5 times, is composed numerical value 5 to register 1; The every circulation of internal layer 1 time, outer cycle count subtracts 1, and the interior loop initial count also subtracts 1; Just equal the numerical value of register 1; So the numerical value of register 1 is composed to register 2, this is because the every circulation primary of internal layer, and according to target order (from small to large or from big to small) exists and leans on the data number of unit, back to increase by 1 again among the RAM; Next round circulation time, number of comparisons can reduce 1 time; Next utilize register 3 and register 4 that two pointers are set: pointer 1 and pointer 2, point to preceding two magnitudes of voltage among the RAM; Then to two magnitudes of voltage relatively size (it is worthy of note here because the AT89C51 single-chip microcomputer that adopts is 8 position digital signal microprocessors, to 12 digital signals relatively size to carry out in two steps; Promptly compare most-significant byte earlier; Relatively hang down 4 again), if 6 magnitudes of voltage are sorted from small to large, if there are the data of the data of front among the RAM greater than the existence back; Will exchange two memory locations of data in RAM, otherwise not exchange the memory location; Next revise pointer, let pointer 1 point to the data that pointer 2 points to, let pointer 2 point to next data, continuation is compared, ordering, up to loop ends; 2 work registers (register 3 with register 4) are set then store the accumulated value of most-significant byte and least-significant byte respectively, it is worthy of note, because the A/D converter of employing AD1674 as totalizer; By left-Aligned rule, there is most-significant byte in the single chip computer AT 89C51 of 8 word lengths in 1 data unit of RAM when receiving the digital voltage of conversion, will hang down 4 and have another data cell (using 0 polishing for low 4 in this element); Before adding up, need least-significant byte to be existed in 1 data unit of RAM by right-aligned principle; There is another data cell (using 0 polishing for high 4 in this element) with high 4; Number of times can be set be 4 circulation, 4 magnitudes of voltage in the middle of size is come are realized the Right Aligns storage with the transposition instruction, when adding up; Accumulative frequency can be set be 3 circulation; To the summation that adds up of 4 magnitudes of voltage of size in the middle of coming, add least-significant byte earlier, and then use carry flag bit CY and increase 8; At last, accumulated value divided by 4, can be used shift order 2 realizations that move to right here.

Shown in accompanying drawing 7; Table look-up and temperature value modular converter will go extreme value filtering to average earlier sample mean that module tries to achieve and each magnitude of voltage in the form module compare by from big to small order; Because the analog voltage signal of gathering reduces with the rising of temperature; So corresponding temperature value is from low to high; Till the magnitude of voltage that finds correspondence or vicinity, the number of times that at this moment compares is exactly the relative address of the magnitude of voltage of correspondence or arest neighbors with respect to the magnitude of voltage of maximum, i.e. sample relative address; Convert the sample relative address relative address of sample mean into then with respect to 0 ℃ of corresponding voltage value; Be about to the sample relative address relative address corresponding relatively,, show that detected temperature value is for just as if the relative address of sample relative address more than or equal to 0 ℃ of correspondence with 0 ℃; Then the sample relative address is deducted the relative address of 0 ℃ of correspondence; Obtain 10 times of absolute value of positive temperature value, because systemic resolution is 0.1 ℃, so what obtain is 10 times of absolute value of temperature value; If the relative address of sample mean is less than 151; Show detected temperature value for negative, then the relative address with 0 ℃ of correspondence deducts the sample relative address, obtains 10 times of absolute value of negative temperature value.Its implementation detail is following: at first the first element address of voltage form composed to program memory ROM pointer DPTR, register 1, register 2 is set then, point to the magnitude of voltage in the form respectively as the least-significant byte and the most-significant byte of pointer, and with its zero clearing; Utilize register 3 and register 4 respectively as the counter of outer and interior loop again, give register 3,95 taxes to register 4, are provided with 950 times bilayer circulation 10 taxes; Utilize DPTR to cooperate the most-significant byte that extracts the digital voltage value in the form earlier with register 1, the value with register 1 adds the least-significant byte that extracts the digital voltage value in the form after 1 more then, and the magnitude of voltage that extracts is deposited among the RAM of data buffer; Next to judge whether adjust the numerical value of pointer; If the numerical value in the register 1 equals 255, then with register 1 zero clearing, the numerical value of while register 2 adds 1, and (most-significant byte of pointer adds 1; The value that is equivalent to pointer adds 256), program memory ROM pointer DPTR adds 256; Then the comparative sample magnitude of voltage with have the size of the magnitude of voltage among the RAM of data buffer; If the sample voltage value is more than or equal to the magnitude of voltage that exists among the RAM of data buffer; Then jump out circulation; With in register 1, the register 2 storage 16 bit pointer numerical value divided by 2; Obtain the relative address (because each magnitude of voltage takies 2 storage unit in the program memory ROM, so 16 bit pointer numerical value of storage are 2 times of actual relative address in the register 1, register 2) of sample mean, if the sample voltage value is less than the magnitude of voltage that exists among the RAM of data buffer; Then continue recycle ratio, till from the form of program memory ROM, finding magnitude of voltage corresponding or arest neighbors; In ensuing corresponding temperature value transformed, the relative address with sample mean compared with 0 ℃ of corresponding relative address 151 earlier, if the relative address of sample mean is more than or equal to 151; Then make the relative address of sample mean deduct 151, obtain the relative address of positive temperature, deposit register 1, register 2 again in respect to zero degree; This moment, the sign bit of positive temperature was not luminous; So make sign bit stroke end code register 3=0, if the relative address of sample mean less than 151, then make 151 deduct sample mean relative address; Obtain the relative address of negative temperature with respect to zero degree; Again deposit register 1, register 2 in, at this moment the sign bit of negative temperature shows negative sign, makes sign bit stroke end code register 3=40H here.

Shown in accompanying drawing 8; Temperature value numeral system modular converter with binary storage in two unit (most-significant byte and least-significant byte) in-15～+ 80 ℃ of scopes 951 possible temperature values be converted into three decimal system numerical value (be respectively ten, individual position and radix point after tenths); And be stored in respectively in three registers, to establish register 4 here and deposit ten value corresponding, register 5 is deposited a position value corresponding; Register 6 is deposited the tenths value corresponding; After the end to be transformed, it is transferred to respectively in three storage unit of random data memory RAM of microprocessor (5), what be worth explanation is; Because resolution is 0.1 ℃; Sample mean is ten times of actual temperature value with respect to the relative address of 0 ℃ of corresponding voltage value, so in transfer process, be stored in numerical value that the whole tuber of stemona in the register 4 divides and be the numerical value on ten when showing; Numerical value when the numerical value that is stored in whole ten parts in the register 5 is demonstration on the position, the numerical value the when numerical value that is stored in a bit position in the register 6 is demonstration on the tenths.Here explain that " [] " symbology in the accompanying drawing 8 is to the operation result round numbers in the bracket, the implementation detail of this module is following: at first register 1 is added in the register 4 divided by 100 integral parts that obtain and goes; From register 1, deduct then and be added to the numerical value that the whole tuber of stemona that goes in the register 4 divides, because positive temperature and negative temperature corresponding voltage value all are no more than 800 with respect to the relative address of 0 ℃ of corresponding voltage value, so the numerical value that most-significant byte register 2 is stored only possibly be 1,2 or 3; If 1, show that the numerical values recited of most-significant byte register 2 storages is 256, let the numerical value in the register 4 add 2; Be added in the register 1 56 then and go, if 2, show that the numerical values recited of most-significant byte register 2 storages is 512; Make the numerical value in the register 4 add 5, be added in the register 1 12 then and go, if 3; Show that it is 768 that most-significant byte is deposited the numerical values recited of 2 storages; Make the numerical value in the register 4 add 7, be added in the register 1 68 then and go, at this moment the numerical value in the register 1 may surpass 100; Go so again register 1 is added in the register 4 divided by 100 integral parts that obtain; From register 1, deduct then and be added to the numerical value that the whole tuber of stemona that goes in the register 4 divides, go up the numerical value that show for such ten and just be stored in the register 4, simultaneously all disallowable the going out of numerical value of whole tuber of stemona branch in register 1 and the register 2; Next; Register 1 stored in the register 5 divided by 10 integral parts that obtain go; And from register 1, deduct the numerical value that is added to whole ten parts of going in the register 5; The numerical value that should show on the position so just is stored in the register 5, simultaneously disallowable the going out of numerical value of whole ten parts in the register 1; Next, what register 1 was stored is the numerical value of a bit position, is stored in the register 6 and goes, and the numerical value that should show on the tenths so just is stored in the register 6; Convert the numerical value in register 4,5 and 6 into stroke end code corresponding when showing through the lattice 2 of tabling look-up at last, and transfer in the random data memory RAM and go, so just accomplished temperature value by scale-of-two to metric conversion.

Shown in accompanying drawing 3 (b) and accompanying drawing 9, the turntable driving module is that microprocessor (5) is passed to chip for driving (6) with the digital signal of position choosing end and stroke end, and chip for driving (6) is driving digital indicator (7) under the control of microprocessor (5), carries out dynamic scan and shows.Its implementation detail is following: at first, the counter of register 3 as the scan cycle number of times is set, and composes and give its numerical value X; If zone bit F0=0 in the processing of module in front; Show that then will carry out normal dynamic scan shows; Before scanning shows; The stroke end of the four figures that prior module will show (containing sign bit) has deposited in order in the random data memory RAM with a position choosing end code and has gone, and utilizes register 1, register 2 as pointer, points to a stroke end and a position choosing end code in the data buffer of the first number respectively; Register 4 is set then as the bit scan cycle counter, shows 4 figure place sign indicating numbers (together with sign bit interior), give its numerical value 4, under cycle control, successively four figures is scanned then so compose because will scan; Here, utilize single-chip microcomputer Pi port (, selecting the P1 port for use here) to transmit stroke end code, utilize the Pj port (here; Select the P3 port for use) open position choosing end code, one (promptly to a new transmission stroke end code) new in scanning will utilize Pj=3FH that charactron is extinguished before, again position choosing end code composed the mouth to Pj; At this moment charactron begins luminous demonstration, and being provided with then pauses prolongs the demonstration time, and then utilizes Pi=0H; Pj=30H extinguishes charactron that (what be worth to stress is, charactron is extinguished, and has multiple to the assignment method of Pi mouth, Pj mouth; But because the ULN2004 driving tube is reverse control, the current potential of Pi mouth, Pj mouth helps reducing unnecessary system power consumption for low, so under the situation that does not influence normal demonstration, selected this assignment method to Pi mouth, Pj mouth); Next, the value of adjustment pointer, the value that is about to register 1, register 2 adds 1; Stroke end under pointing in the data buffer of 1 figure place and a position choosing end code, continuation scanning shows, up to loop ends; If zone bit F0=1 then reports to the police, utilize Pi=3FH, Pj=0H makes group of four figures pipe all show zero, and red light is bright, hummer rings;

The form module comprises two parts; Form 1 is the corresponding digital voltage value of different temperatures value; Design voluntarily and adopt the NTC thermistor of low temperature sintering technology preparation to provide in-15～+ 80 ℃ of temperature ranges, with 2.5 ℃ be the corresponding resistance value of each temperature value of step-length, between per 2 temperature values, utilize the method for linear interpolation to try to achieve in this temperature range; With 0.1 ℃ is the corresponding resistance value of each temperature value of step-length; Thereby obtaining in-15～+ 80 ℃ of scopes with 0.1 ℃ is the corresponding resistance value of each temperature value of step-length, according to formula (2), is translated into the corresponding digital magnitude of voltage again; Deposit in the program memory ROM of microprocessor (4), as the form 1 of temperature transition; Form 2 is corresponding binary numerals of stroke end code of digital indicator (7) from 0 to 9.

The characteristics of digital displays temperature detection method of the present invention are: table look-up and the temperature value modular converter is by the program of the algorithm establishment of tabling look-up of design voluntarily; Be with the difference of the common algorithm of tabling look-up: in the program memory ROM of AT89C51 single-chip microcomputer; Only deposit in-15～+ 80 ℃ of temperature ranges; With 0.1 ℃ is the pairing magnitude of voltage of temperature at interval; And do not deposit the corresponding temperature value of magnitude of voltage in, and table look-up that what obtain is the corresponding relative address of detected magnitude of voltage, convert relative address into corresponding Temperature numerical then; Can save the storage space of the program memory ROM of AT89C51 single-chip microcomputer like this, can further enlarge temperature measurement range and improve detection resolution;

The characteristics of digital displays temperature detection method of the present invention also are: temperature value numeral system conversion module; Also be by the program of the algorithm establishment of design voluntarily, can (resolution be 0.1 ℃ with 951 possible temperature values in-15～+ 80 ℃ of scopes that are stored in two storage unit (register 1 storage most-significant byte, register 2 storage least-significant bytes); Temperature range is-15～+ 80 ℃) utilize the single-chip microcomputer of 8 word lengths that it is transformed into the decimal system from scale-of-two; And be stored in three storage unit ten value corresponding of i.e. register 4 storages, register 5 a storages position value corresponding respectively; Register 6 storage tenths value corresponding; Because resolution is 0.1 ℃, it is ten times of actual temperature value that temperature value is stored in numerical value in the corresponding units, so the numerical value that positive temperature (maximum 800) is stored in the corresponding units all possibly surpass 256; Be stored in two storage unit; Existing numerical value converting algorithm can not satisfy the conversion requirement, must combine in the conversion judgement of the numerical value in the most-significant byte storage unit is transformed, and this algorithm is revised the numeral system conversion that expansion goes for the temperature value of bigger temperature range a little.

After system powers on, green lumination of light emitting diode, system starts working; When temperature is in-15～+ 80 ℃ of scopes; The normal displays temperature of thermometer, when temperature surpassed-15～+ 80 ℃ of scopes, red lumination of light emitting diode cooperates reported to the police with the sound of hummer.

Claims (6)

1. digital displays temperature detection system; By negative temperature coefficient (abbreviating NTC as) thermistor (temperature) sensor probe (1), analog voltage signal Acquisition Circuit (2), instrumentation amplifier (3), A/D converter (4), microprocessor (5), chip for driving (6); Nixie display (7) connects to form successively, it is characterized in that:

A. analog voltage signal Acquisition Circuit (2) adopts Wheatstone bridge simple in structure, by NTC thermistor R _tWith 3 resistance value perseverances be R ₀Resistance R ₁, R ₂And R ₃As the brachium pontis of electric bridge, R _tOne end ground connection, the diagonal angle termination DC voltage U of ground connection ₀, R _tThe other end is a high-voltage output terminal, and its magnitude of voltage is U ₊, the diagonal angle end of high-voltage output terminal is the low-voltage output terminal, its magnitude of voltage is U _-, the voltage stabilizing sheet is that electric bridge provides DC voltage U ₀, the analog voltage signal of electric bridge two ends output is to import the analog voltage signal U that instrumentation amplifier (3) gains _In=U ₊-U _-

B. instrumentation amplifier (3) is by instrumentation amplifier integrated circuit and feedback resistance R _GForm, the size of gain is by feedback resistance R _GValue regulate;

C. microprocessor (5) adopts the single-chip microcomputer of 8 word lengths, receives and handle the digital voltage signal of 12 A/D converter (4) transmission;

D. chip for driving (6) is made up of 14 Darlington pipes, under the control of microprocessor (5), drives nixie display (7), carries out dynamic scan and shows.

2. digital displays temperature detection system as claimed in claim 1 is characterized in that: according to the resistance R of the bridge resistor in systemic resolution and measurement range and the analog voltage signal Acquisition Circuit (2) ₀, bridge voltage U ₀And the analytic relationship of the gain G of instrumentation amplifier (3) is set up circuit parameter R ₀, U ₀With the criterion of choosing of G, at first, confirm R ₀Value, make R ₀As far as possible near R _tMinimum value, i.e. the corresponding resistance value of maximum temperature; Next, confirm bridge voltage value U ₀Product GU with the instrumentation amplifier gain G ₀Value, U ₀Product GU with G ₀Confirm to be divided into resolution

Preferentially guarantee preferentially to guarantee two kinds of situation, if resolution is preferentially guaranteed the R that at first will confirm with measurement range ₀Value, minimum temperature value T that expection detects and the resistance R of its corresponding NTC thermistor _tSubstitution resolution expression formula

By the resolution that will guarantee Try to achieve U ₀Product GU with G ₀Span and therefrom choose value less and that realize easily, then, with the R that has confirmed ₀Value, GU ₀Value and the resistance R of the minimum temperature value T corresponding N TC thermistor that detects with expection _tThe maximum analog voltage expression formula of max substitution instrumentation amplifier output

If U in the formula _OutThe value of max is not more than A/D converter and requires the highest analog voltage imported, and then the minimum temperature value T that detects of explanation expection can realize, and can sound out by above-mentioned steps and choose littler lowest detection temperature value, otherwise, if U in the formula _OutThe value of max is greater than the highest analog voltage of A/D converter requirement input, and then the minimum temperature value T of explanation expection detection cannot realize, should choose bigger lowest detection temperature value by the above-mentioned steps exploration, confirms GU again ₀Value; If measurement range is preferentially guaranteed, the R that at first will confirm ₀Value and the resistance R of the minimum temperature value T corresponding N TC thermistor that detects with expection _tThe maximum analog voltage expression formula of max substitution instrumentation amplifier output

Make U _OutMax is not more than the highest analog voltage of A/D converter requirement input, thereby tries to achieve U ₀Product GU with G ₀Span, and therefrom choose value bigger and that realize easily, the R that next will confirm ₀Value, GU ₀Value, minimum temperature value T that expection detects and the resistance R of its corresponding NTC thermistor _tSubstitution resolution expression formula

Try to achieve resolution

Thereby try to achieve the temperature step-length of detection, promptly the voltage step size of A/D converter/

At last, according to side circuit and system works performance demands, distribute U ₀With G value separately.

3. digital displays temperature detection system as claimed in claim 1; It is characterized in that: temperature sensor probe (1) is the chip NTC thermistor that adopts the preparation of low-temperature sintering new technology; Be fixed in the brass shell with epoxy resin, process the sensor probe of temperature detection.

4. digital displays temperature detection method based on the described digital displays temperature detection system of claim 1; By signals collecting touch piece, go extreme value filtering average module, table look-up and temperature value modular converter, temperature value numeral system modular converter, turntable driving module and form module are formed, it is characterized in that: comprise the steps:

6 call signal acquisition modules are gathered analog voltage signal through A/D converter (4), and are converted it into digital signal, send microprocessor (5) to, gather 6 sample voltage values;

Calling the extreme value filtering module of averaging averages: before each update displayed temperature value; 6 digital voltage signals gathering are sorted with the bubbling method; After removing maximal value and minimum value; Again remaining 4 digital voltage signals are added up the back divided by 4, thereby try to achieve mean value, be i.e. sample mean;

Whether judgement sample mean value surpasses the scope of magnitude of voltage in the form, if, then make the F0 zero clearing of microprocessor (5), directly call the turntable driving module and carry out alarm indication;

Otherwise, make the F0 set of microprocessor (5), call and table look-up and the temperature value modular converter converts magnitude of voltage into temperature value; Call temperature value numeral system modular converter again, convert the scale-of-two temperature value that is stored in two unit of most-significant byte and least-significant byte into three decimal system numerical value, be respectively the tenths behind ten, individual position and the radix point; Call the turntable driving module at last, controlling and driving chip (6) sends the shows signal of nixie display (7) position choosing end and stroke end to, shows thereby carry out dynamic scan.

5. digital displays temperature detection method as claimed in claim 4; It is characterized in that: table look-up and the temperature value modular converter is in the program memory ROM of single-chip microcomputer; Only deposit in-15～+ 80 ℃ of temperature ranges, with 0.1 ℃ be the pairing magnitude of voltage of each temperature value at interval, and do not deposit corresponding temperature value in; Tabling look-up, what obtain is the corresponding relative address of sample mean, and then converts relative address into corresponding Temperature numerical; Its operation steps is following: will go extreme value filtering to average earlier sample mean that module tries to achieve and each magnitude of voltage in the form module compares by order from big to small; Because the analog voltage signal of gathering reduces with the rising of temperature; So corresponding temperature value is from low to high; Till the magnitude of voltage that finds correspondence or vicinity, the number of times that at this moment compares is exactly the relative address of the magnitude of voltage of correspondence or arest neighbors with respect to the magnitude of voltage of maximum, i.e. sample relative address; Convert the sample relative address relative address of sample mean into then with respect to 0 ℃ of corresponding voltage value; Be about to the sample relative address relative address corresponding relatively,, show that detected temperature value is for just as if the relative address 151 of sample relative address more than or equal to 0 ℃ of correspondence with 0 ℃; Then the sample relative address is deducted the relative address of 0 ℃ of correspondence; Obtain 10 times of absolute value of positive temperature value, because systemic resolution is 0.1 ℃, so what obtain is 10 times of absolute value of temperature value; If the relative address of sample mean is less than 151; Show detected temperature value for negative, then the relative address with 0 ℃ of correspondence deducts the sample relative address, obtains 10 times of absolute value of negative temperature value.

6. digital displays temperature detection method as claimed in claim 4; It is characterized in that: temperature value numeral system modular converter; It is three decimal system numerical value with it from Binary Conversion that 951 possible temperature values in-15～+ 80 ℃ of scopes that are stored in two storage unit of most-significant byte and least-significant byte are utilized the single-chip microcomputer of 8 word lengths; And be stored in respectively in three registers; Be ten value corresponding of register 4 storages, register 5 a storages position value corresponding, register 6 storage tenths value corresponding; The operation steps of this module is following: at first least-significant byte register 1 is stored in the register 4 divided by 100 integral parts that obtain and go, from register 1, deduct then and store the numerical value that the whole tuber of stemona that goes in the register 4 divides into, because positive temperature and negative temperature corresponding voltage value all are no more than 800 with respect to the relative address of 0 ℃ of corresponding voltage value; So the numerical value of most-significant byte register 2 storages only possibly be 1,2 or 3, if 1, show that the numerical values recited of most-significant byte register 2 storages is 256; Let the numerical value in the register 4 add 2, be added in the register 1 56 then and go, if 2; The numerical values recited that shows 2 storages of most-significant byte register is 512; Make the numerical value in the register 4 add 5, be added in the register 1 12 then and go, if 3; Show that it is 768 that most-significant byte is deposited the numerical values recited of 2 storages; Make the numerical value in the register 4 add 7, be added in the register 1 68 then and go, at this moment the numerical value in the register 1 may surpass 100; Go so again register 1 is added in the register 4 divided by 100 integral parts that obtain; From register 1, deduct then and be added to the numerical value that the whole tuber of stemona that goes in the register 4 divides, go up the numerical value that show for such ten and just be stored in the register 4, simultaneously all disallowable the going out of numerical value of the whole tuber of stemona branch of the temperature value of storage in register 1 and the register 2; Next; Least-significant byte register 1 stored in the register 5 divided by 10 integral parts that obtain go; And from register 1, deduct the numerical value that stores whole ten parts of going in the register 5 into; The numerical value that should show on the position so just is stored in the register 5, simultaneously disallowable the going out of numerical value of whole ten parts in the least-significant byte register 1; Next, what least-significant byte register 1 was stored is the numerical value of a bit position, is stored in the register 6 and goes, and the numerical value that should show on the tenths so just is stored in the register 6; So just accomplished temperature value by scale-of-two to metric conversion.

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