实验时，将应变片粘贴在试件表面需测应变的点处和方向上，当该点沿应变片方向产生应变?时，应变片也随之变形，致使应变片的电阻值产生一个变化量ΔR。
21 三. 应变仪电桥原理
?R1R3?R2R4??Ui??U??R?R??R?R??04??123Ifor?RK?RR1R3?R2R4ThenE?0R1R2?R4R3i.e.A balanced bridge?xR1R2?Ui?U02?R1?R2???R1?R2?R3?R4??????RRRR234??122 R1两端的电压降为： 23 温度补偿片
在实验中,如果温度发生变化, 应变片的阻值将随之改变, 故测量结果中也将包括温度改变引起的虚假应变。
为了消除温度的影响，常采用补偿片法。即在与被测试件材料相同的另一试块上，粘贴上与工作片型号相同的电阻片，并放置在与被测试件相同的环境下，且不受力。
24 导线的影响 Effect of Lead Wires:
Consider a strain measuring device with a single remote active gauge connected to The completion bridge inside the instrument.
Where RL = Lead wire resistance connections: A,B,C,&D are inside the instrument.
For 1 Active Gauge: Subjected to ?
?E?V??Rg?2RL?R2??Rg?R2??g?2RL?R2???Rg?2RL??R1??Rg?2RL?But?RgR?Sg?g?E?V?Rg?2R?L?RgR2R?2RR2gL?2??Rg?2RSg?L??VR?gR2R2g?2RL?R2?Sg?25 温度补偿片接法
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