The Cold Hot Dual Thermostat
[Abstract] This design through measured the warm electric circuit, through warmcontrols the output circuit again, achieves the cold hot dual purposeconstant temperature using the semiconductor refrigeration or system hottechnology the goal. The temperature gathering electric circuitchooses the platinum resistance to measure the warm electric circuit,including (had voltage comparison function) with platinum resistancePT1000,and the chip LM2902 combination .
The semiconductorrefrigeration or system hot electric circuit mainly uses thesemiconductor temperature difference to refrigerate the module. The semiconductor temperature difference refrigeration system hotmodule generally is composed by certain thermo couple component, theyon the electricity are series connected, the electric current passeseach thermo couple component in turn. These thermos couple in the heatchange are parallel, through changes the variable current to realizeafter the thermo couple electric current heats up with the temperaturedecrease, is precisely the semiconductor temperature differencerefrigeration/system hot module has counter uses the function, mayconveniently realize the refrigeration and the system hottransformation.
[KeyWords] The thermostat;measured the warm electric circuit;warm controls heelectric;circuit,pearl's card effect;the thermistor
3.1测温电路(circuit of temperature survey)设计
测温电路有很多,包括二阶式电桥电路,集成式半导体传感器电路,基于单片机的温度控制器等等方案。
二阶式电桥电路法这种温度推测器精度可达0.1℃以上, 传统的不平衡电桥作为电阻温度变送器的测量电路,在温度测量和控制中起着极其重要的作用。这种电路也经常作为单片机的一种前向通道接口使用,进而构成智能化测量控制仪表,但是,不平衡电桥中存在的非线性特性一直是人们需要彻底解决的问题。除此之外,在设计中,还要考虑自热温升、引线电阻、零点迁移等因素。所以此设计不采用。
综合上述设计中存在的优缺点,本设计采用铂电阻测温电路方案。 热电阻和热电偶是工业生产过程自动化最常用的两种温度传感器。热电阻由于在测量的灵敏度、线性度等诸多方面均优于热电偶,因此,在中低温区得到了更广泛的应用。