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The relevant time constant is the product of the effective capacitance in microfarads and the
$ I" J v, U5 B7 D& d* [9 a0 B: Keffective discharge resistance in megohms. If it is difficult to determine the effective
3 D: Z- F0 B$ r5 Dcapacitance and resistance values, a measurement of voltage decay at the point of external( n& M& p! ~$ o
disconnection can be used. When conducting the voltage decay measurement, the result is
9 \# F5 J! w/ K3 f) ]5 Z& treferred to an instrument having an input impedance consisting of a resistance of
1 O9 z5 n) L$ q5 U/ F& ]7 } K100 MΩ ± 5 MΩ in parallel with an input capacitance of 20 pF ± 5 pF.% a; h3 F7 L: G) l7 c
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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