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The relevant time constant is the product of the effective capacitance in microfarads and the# }- m0 S- R- T
effective discharge resistance in megohms. If it is difficult to determine the effective
5 o2 C* h. a, `capacitance and resistance values, a measurement of voltage decay at the point of external
$ F4 |8 c0 ^3 x* s8 edisconnection can be used. When conducting the voltage decay measurement, the result is
. Y# B; D+ R" ^referred to an instrument having an input impedance consisting of a resistance of
! U$ t0 B8 s1 r% ~$ w: I: u100 MΩ ± 5 MΩ in parallel with an input capacitance of 20 pF ± 5 pF.2 N/ {' }- Z2 b$ R1 M
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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