“现在咖啡价格涨得这么高，有些农民很担忧”，李中恒说。
"Some farmers are worried that coffee prices have risen so high now," said Li.
采用恒流法，可以使用静电计电压表和电流源或者只使用静电计欧姆计来测量高电阻。
High resistance measurements using the constant-current method may be made using either an electrometer voltmeter and current source or just an electrometer ohmmeter.
串级JFET恒流器件具有非常高的动态阻抗。
Cascade JFET constant current device is of very high dynamic impedance.
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