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The relevant time constant is the product of the effective capacitance in microfarads and the5 J" J( c; n3 o5 q9 A
effective discharge resistance in megohms. If it is difficult to determine the effective
3 E ]6 P# V, H% b( Ecapacitance and resistance values, a measurement of voltage decay at the point of external- q) s8 C$ c2 r
disconnection can be used. When conducting the voltage decay measurement, the result is: p% `: p1 v$ T% r
referred to an instrument having an input impedance consisting of a resistance of
: P3 H$ [6 B7 |& m1 V I7 w( D100 MΩ ± 5 MΩ in parallel with an input capacitance of 20 pF ± 5 pF.
. Y: ^5 V& F8 W' m$ S& H5 \3 t! @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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