壓阻式傳感器的應變與溫度交叉靈敏度分析
Analysis of the Strain of Piezoresistive Sensor and Temperature Crossed Sensitivity
ZHAO Fan
(Shanxi University of Technology, Hanzhong 723003, China)
Abstract: With the help of Thaler expanding formu la of dualistic function, the author gave the formula of computing the strain a nd temperature crossed sensitivity, explained the physical meaning. Combining real measurement data, he evaluated the crossed sensitivity.
Key words: piezoresistive sensor; strain; temperature; crossed s ensitivity
壓阻式傳感器是在圓形硅膜片上擴散出四個電阻,這四個電阻接成惠斯登電橋。假設四個擴散電阻的起始電阻都相等且為R,當有應力作用時,兩個電阻的阻值增加,增加量為ΔR,兩個電阻的阻值減小,減小量為ΔR;另外由于溫度影響,使每個電阻都有ΔRT的變化量。若電橋的供橋電壓為U,則它的輸出電壓為:
式中:πL—壓阻系數(shù);E—電阻半導體材料的彈性模量;S=πL·E—傳感器的靈敏度。
根據四個電阻本身的溫度特性,設它們的溫度系數(shù)為α,則:
當傳感器受應變ε和溫度T的作用,則由泰勒公式在初始應變ε0和環(huán)境溫度T0下將式(4)展開得:
靈敏度,當不考慮溫度影響時,該項為常值;SεT=USα,定義為應變與溫度的交叉靈敏度。
第三項、第四項及以后各項為溫度變化項,忽略掉ΔT的高階項,溫度與傳感器的輸出呈線性關系,令ST=USεα,定義為傳感器的溫度靈敏度。忽略掉高階項,式(6)又可寫為:
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