The picoammeter reads the current at the last dynode, which is equal to the anode current minus the current flowing to the previous dynode.

皮计在最后一个倍增电极处读取电流，此电流等于阳极电流减去流过前一个倍增电极的电流。

The big disadvantage is the loss of accuracy and resolution, but some digital picoammeters combine accuracy and dynamic range by combining autoranging and digital log conversion.

这种方法，较大的缺点是损失了准确度和分辨率。然而，也有些数字式皮，用自动量程和数字对数变换的方法，这可将准确和宽动态范围结合了起来。