CN102680121A - Intelligent indoor temperature acquirer - Google Patents

Abstract

An intelligent indoor temperature acquirer is a temperature measurer for indicating indoor temperature. A temperature sensor acquires and processes temperature signals, the temperature signals are transmitted to a signal processor to be processed and calculated, and results are displayed on a display device or transmitted to other equipment via a communication unit. Nonlinear errors are reduced by a DS18B20 temperature measuring principle, linear errors are reduced by piecewise linearity and a least square method, and temperature measurement accuracy is improved. A low-power-consumption element is adopted, and the intelligent indoor temperature acquirer is powered by a lithium battery which is charged by solar energy.

Description

The indoor temperature intelligent collector

Technical field:

The present invention is a kind of temperature measuring equipment of indicating indoor temperature, is a employing high precision measuring temperature element, and the smart electronics product of low power consumption integrated circuit design is widely used in the heating power industry and other need be measured in the environment of indoor temperature.

Background technology:

At present, known intelligent temperature measurement device is made up of temperature sensing unit, signal conversion unit, signal processing unit, temperature display unit and communication unit etc.At first by temperature sensing unit collecting temperature signal and handle; After converting digital signal to through signaling conversion circuit again; Give signal processing unit and carry out signal Processing and calculating, the result shows on display device or passes to miscellaneous equipment through communication unit.This traditional temp measuring method is because the non-linear measurement range that causes of temperature element is little, and temperature measurement error is big, is not suitable in the high-precision thermometric environment.In addition, adopt the traditional circuit design, volume is big.Power consumption is high, in practical application, has problems such as installation, power taking trouble.

Summary of the invention:

Shortcomings such as the temperature measurement error that existing temperature measuring equipment exists is big in order to overcome, power consumption height the invention provides a kind of temperature measuring equipment, and this installs not only, and temperature measurement accuracy is high, and is low in energy consumption, and adopts solar recharging, and stand-by time is long, energy-conserving and environment-protective.

The present invention solves the technical scheme that its technical matters takes:

1) adopts the design of low power dissipation electron components and parts

This temperature measuring equipment circuit is principle of design with the low-power consumption.Temperature probe adopts a unibus programmable, intelligent temperature sensor DS18B20; It is integrated in A/D converter, register, interface circuit in the chip; Can directly export digital signal, its volume is little, system architecture is simple, is a kind of temperature measurement device of miniature, low-power consumption.Microprocessor adopts ATmega8, and ATmega8 is based on 8 CMOS microcontrollers of low-power consumption of the AVR risc architecture of enhancing, has five kinds of park modes, power consumption 1.0mA during idle pulley, power consumption 0.5 μ A during power-down mode.Show and adopt segmentation liquid crystal HT1621 to drive low-power consumption LCD, working current 0.1mA.

2) utilizing software that temperature element is carried out linearity revises and compensates

Utilize temperature-measurement principle to reduce nonlinearity erron: since the resolution of DS18B20 be 9～12 able to programme, in order to obtain the temperature of degree of precision, can adopt 12 bit patterns, minimum temperature resolution is 0.0625 ℃ in theory.But owing to influenced by various factors, the resolution actual value that DS18B20 measures temperature has only 0.5 ℃, and the inner structure of the ingenious combination of native system design DS18B20 further improves its resolution.

Adopt piecewise linearity and least square method to reduce linear error: through can obtaining 0.1 ℃ of error in the scope on the above theoretical method, but owing to receive the influence of various factors.Often error range can reach 0.5 ℃.Through analyzing, learn that error is mainly derived from chip internal semiconductor heat noise.Its type is a linear error, and error increases with the rising of temperature.In order to improve measuring accuracy, should adopt different correction factors for the different temperature interval, utilize effective mathematical model, further improve temperature measurement accuracy.

3) adopt lithium battery power supply, solar recharging

System's power pack adopts the lithium ion battery power supply, and volume is little, capacity is big, installing and replacing is convenient.Adopt the solar charging power mode during operate as normal, in particular cases, can switch to the DC5-24V charge mode through change-over switch.

The invention has the beneficial effects as follows, can reduce temperature measurement error, error range is reached in 0.1 ℃; Can realize low-power consumption, effectively utilize solar powered, energy-conserving and environment-protective.

Description of drawings:

Fig. 1: system construction drawing

Fig. 2: reduce the nonlinearity erron schematic diagram.

Embodiment:

In Fig. 1, temperature sensor DS18B20 induced environment temperature is after the internal circuit processing; Digital signal is sent to microprocessor ATmega8, and signal is delivered to LED and is shown after the ATmega8 computing, simultaneously through the D/A conversion; Become 4-20mA signal output (function is optional); Temperature signal also can be read by external unit through communication modes, supports the RS232/485 interface, standard Modbus rtu protocol.Power supply indication, communication state and malfunction in the equipment operation shown by the state indicating member.Power unit is made up of lithium battery, solar panel and direct current 5-24V power interface, can switch powering mode through toggle switch.

In Fig. 2, the high-temperature coefficient oscillator is confirmed a gate cycle, can measure temperature through the clock number of low-temperature coefficient oscillator is counted just at this gate in the cycle then.In counter and temperature register, all preset the initial value corresponding to-55 ℃, if before the gate end cycle, the value of counter does not reduce to zero, just shows that current measurement temperature is higher than-55 ℃, and the value in the temperature register will increase.Simultaneously, the slope totalizer presets initial value to counter again, and counter count down to zero again.If the gate cycle is counting not, then repeat said process.

Utilize following formula can calculate high-resolution temperature value:

T＝temp_read-0.25+(count_per_degree-count_remain)/count_per_degree

Wherein, the temperature reading of reading among the temp_read:DS18B20;

Count_per_degree: every degree centigrade count value;

Count remain: the remainder in the gate end cycle hour counter.

Through can obtaining 0.1 ℃ of error in the scope on the above theoretical method, but owing to receive the influence of various factors, often error range can reach 0.5 ℃.Through analyzing, learn that error is mainly derived from chip internal semiconductor heat noise, its type is a linear error, and error increases with the rising of temperature.In order to improve estimated accuracy, should adopt different correction factors for the different temperature interval.If this system linearity error model is following:

T＝KTγ+C

Wherein, T is a measured value, and T γ is actual value (adopting more, high precision MS6506 measurement gets), and K is temperature variant linear error correction factor, and C is the error compensation parameter.

After having set up the error model of DS18B20, come the parameter of evaluated error model through test.If by estimator X is n dimension random vector,, it is carried out the observation of k sublinear obtains in order to obtain its estimator:

z＝HiX+V，(i＝1，2，…k)

This formula can be write as:

$Z=\left[\begin{array}{c}{Z}_1\\ Z_2\\ \·\·\·\\ Z_4\end{array}\right]H=\left[\begin{array}{c}{H}_1\\ H_2\\ \·\·\·\\ H_4\end{array}\right]V=\left[\begin{array}{c}{V}_1\\ V_2\\ \·\·\·\\ V_4\end{array}\right]$

Wherein, Z is a m dimension observation vector, and Hi is that mXn observing matrix average is zero m dimension observational error vector.When km＞n, because the number of equation more than the number of unknown number, therefore can be estimated X according to Z.If require to select the estimation of X, make following performance index reach minimum, so, just claim that this is estimated as the least-squares estimation of X.Above-mentioned least-squares estimation is a deterministic minimizing problem, therefore can realize the null method of the gradient of X through making J (X).

Make gradient formula equal zero, then as (H ^TWhen H) being nonsingular matrix, can get:

X _TS(Z)＝(H ^TH) ^-1H ^TZ

Following formula is exactly the least square optimal estimation formula of being tried to achieve by observation data Z, wherein X _TS(Z) be the linear function of observation data Z.

Data (table 1 is listed) by the experiment gained:

Before DS18B20 revises	High-precision temperature meter (Ms6506)	After DS18B20 revises
			?25.0625	25.54	?25.5000
?28.1250	28.50	?28.5000
			?31.1870	31.52	?31.4375
?34.9375	35.00	?35.1250
			?37.8750	38.00	?37.9375

Table 1: experimental data table

The data of getting before these five DS18B20 revise are the Z vector, and the data of high-precision temperature meter (MS6506) are the H vector, and estimative temperature is the X vector:

$Z=\left[\begin{array}{c}25.0625\\ 28.1250\\ 31.1870\\ 34.9375\\ 37.8750\end{array}\right]$ $H=\left[\begin{array}{cc}25.54& 1\\ 28.50& 1\\ 31.52& 1\\ 35.00& 1\\ 38.00& 1\end{array}\right]$ $X=\left[\begin{array}{c}K\\ C\end{array}\right]$

Adopt the optimal estimation formula of least square method to calculate K=1.0408.C=-1.5256, this correction factor obtains under 25 ℃～40 ℃ temperature.Also can adopt same procedure to obtain correction factor in other temperature ranges.

Claims (3)

1. indoor temperature intelligent collector; By temperature sensor collecting temperature signal and handle, give signal processor and carry out signal Processing and calculating, the result shows on display device or passes to miscellaneous equipment through communication unit; It is characterized in that: utilize software that temperature element is revised and compensated; Adopt the design of low power dissipation electron components and parts, lithium battery power supply, solar recharging.

2. indoor temperature intelligent collector according to claim 1 is characterized in that: utilize the temperature-measurement principle of DS18B20 to reduce nonlinearity erron, adopt piecewise linearity and least square method to reduce linear error.

3. indoor temperature intelligent collector according to claim 1 is characterized in that: adopt the design of low power dissipation electron components and parts, lithium battery power supply, solar recharging.

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