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The relevant time constant is the product of the effective capacitance in microfarads and the, j" _ i7 \) ]4 b J& ?2 q) z4 v
effective discharge resistance in megohms. If it is difficult to determine the effective* x. W6 H5 I+ f- h Q8 [, @( o
capacitance and resistance values, a measurement of voltage decay at the point of external- V# m! m/ V% l. x
disconnection can be used. When conducting the voltage decay measurement, the result is' t' T8 o, g) X9 ` m
referred to an instrument having an input impedance consisting of a resistance of
4 @0 C5 S4 Q' h. r6 W100 MΩ ± 5 MΩ in parallel with an input capacitance of 20 pF ± 5 pF.4 [3 I/ d, _3 p2 Q9 b
从标准的内容来说,确实是要求100 MΩ ± 5 MΩ 阻抗,但是我个人觉得阻抗越大,分流就越小,测到的数据就越接近真实情况。但标准不知道是怎么考虑的,为什么不在100M前面加上at least 之类的字眼。 |
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