惠斯通电桥测电阻实验中,如果电阻箱R2无法准确读数,能否测出Rx
\u60e0\u65af\u767b\u7535\u6865\u5b9e\u9a8c\u4e2d\uff0c\u7535\u963b\u7bb1R2\u65e0\u6cd5\u51c6\u786e\u8bfb\u6570\uff0c\u80fd\u5426\u6d4b\u51faRx\uff1f\u4e0d\u80fd\u3002\u7531\u5b9e\u9a8c\u539f\u7406\u77e5Rx\uff1dR2/R3*R4\uff0c\u6240\u4ee5\u4e09\u4e2a\u7535\u963b\u4e2d\u7684\u4efb\u4f55\u4e00\u4e2a\u65e0\u6cd5\u51c6\u786e\u8bfb\u6570\uff0c\u90fd\u5c06\u5bfc\u81f4Rx\u4e0d\u80fd\u6d4b\u51fa\u3002\u671b\u91c7\u7eb3\u54e6\uff5e
\u9996\u5148\u7535\u963b\u7bb1\u4e0a\u6709\u7cfb\u7edf\u8bef\u5dee\u9650\uff0c\u8fd9\u4e2a\u8981\u6284\u4e0b\u6765\u7684\uff0c\u6ca1\u6284\u7684\u8bdd\u5c31\u53d6\u91cf\u7a0b\u4e0b\u6700\u5c0f\u523b\u5ea6\u7684\u4e00\u534a\uff0c\u5c31\u662f\u4f60\u6d4b\u6bcf\u4e2a\u7535\u963b\u7684\u4e0d\u786e\u5b9a\u5ea6\u3002\u4f60\u7684\u8ba1\u7b97\u5f0f\u662fRx=R1*R2/R3\u5427\uff0c\u5bf9R1R2R3\u5206\u522b\u6c42\u504f\u5bfc\u53d6\u7edd\u5bf9\u503c\u76f8\u52a0\uff0c\u6709dRx=(R2/R3)*dR1+(R1/R3)*dR2+(R1*R2)/(R3*R3)*dR3\uff0c\u5176\u4e2ddR1\uff0cdR2\uff0cdR3\u4e3a\u6bcf\u4e2a\u7535\u963b\u7684\u4e0d\u786e\u5b9a\u5ea6\uff0c\u76f8\u5bf9\u4e0d\u786e\u5b9a\u5ea6\u4e3adRx/Rx
可以。经过换臂以后待测电阻 Rx = R4 = sqrt(_R4 * _R'4)，无需知道R2与R3准确值，只需R2和R3保持不变即可不能，因为：
RX=(R1/R2)XRS
即使电桥平衡，不确定R2也无法测RX.
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