The buffers can be a pair of JFET op amps or two electrometers with unity-gain outputs.
该缓冲器可以是一对JFET运算放大器或者是两个具有单位增益输出的静电计。Electrometers can be very useful where electrode areas are very small and solution conductivities are very low.
当电极面积非常小而溶液的导电率非常低时，静电计是非常有用的。In addition to their versatility, electrometers are easy to operate, reliable, and rugged.
静电计的其它特点是容易操作，可靠和坚固耐用。To measure the offset of a switch card, connect the output of the card to a pico ammeter or electrometer.
若要测量开关卡的偏移电流，请将卡的输出连接到一台皮安计或静电计。Figure 2-39 shows an electrometer connected to a current source that consists of a voltage source in series with a resistor.
图2-39所示为静电计和由电压源及电阻器串联组成的电流源相连接。Refer to the electrometer's manual or specifications for the value of the feedback impedance for a particular instrument.
特定仪器反馈阻抗的数值请参见该静电计的手册或技术指标。When a charged object is placed within the inside electrode, an induced charge will flow into the electrometer.
当带电物体放到内电极里面的时候，就有感生电荷流过静电计。The instruments used to make these high impedance measurements include electrometers, picoammeters, and source-measure units (SMUs).
用来测量这些高阻源的仪器包括静电计、皮安表和源-测量单元（SMU）。Quartz has properties similar to sapphire, but considerably higher piezoelectric output, so it's rarely used in electrometer circuits.
石英具有类似于蓝宝石的性质，但是其压电输出相当高，所以很少用于静电计电路中。