模拟开关MAX4590在测温电路中的应用

中文字数:1139,中文页数:2  英文字数:759页数:2

 In the thermal resistance type temperature sensor's temperature measurement electric circuit, the sensor composition electric bridge, and with the constant pressure source is the electric bridge power supply generally, according to electric bridge's output voltage determined must survey ambient temperature. As a result of the resistance thermal reaction limit, the electric bridge power source's peak-to-peak value cannot be excessively high, will otherwise affect the measuring accuracy, even possibly creates sensor's damage. The electric bridge outputs the voltage is very usually small, needs to carry on enlargement processing; Moreover, electric bridge's output voltage and the thermal resistance resistance value is not the absolute linear relationship, but also needs to increase the hardware or the software carries on linearized processing. Along with measurement circuit quantity's increase, the cost and the power loss of the system will also become a not allow to neglect question. Following introduced that one kind of simple temperature measurement electric circuit, it may solve the above problem effectively.

 在热电阻式温度传感器的测温电路中，一般将传感器组成电桥，并用恒压源为电桥供电，根据电桥的输出电压来确定所要测量的环境温度。由于电阻的热效应限制，电桥电源的幅值不能过高，否则将影响测量精度，甚至可能造成传感器的损坏。电桥输出的电压通常很小，需要进行放大处理；另外，电桥的输出电压与热电阻的电阻值不是绝对的线性关系，还需要增加硬件或软件进行线性化处理。随着测量回路数量的增多，系统的成本及功耗也将成为一个不容忽视的问题。下面介绍一种简单的测温电路，可以有效地解决上述问题。
 由于电阻的热效应，热电阻（电阻值从1Ω到几千欧姆不等）的工作电流都有一定的限制，而热电阻的温度系数小于0.67%/℃，即对于电阻值为100Ω的热电阻，温度变化1℃，电阻值变化到1Ω。要提高测量精度，只有提高工作电流，考虑到热效率与电流的平方成正比，若要将工作电流提高两倍，应选择占空比为1：4 的脉冲电流。附图所示电路就是根据这一原理设计的。

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