对测量的基本限制是源电阻中的约翰逊噪声。
The fundamental limit to measurement is Johnson noise in the source resistance.
有效电阻为源电阻和反馈(或分流)取样电阻的并联组合。
The effective resistance is the parallel combination of the source resistance and the feedback (or shunt) sensing resistance.
降低源电阻的温度、减小测量的带宽可以降低约翰逊噪声。
Johnson noise may be reduced by lowering the temperature of the source resistance and by decreasing the bandwidth of the measurement.
讨论了带宽和温度以后，决定系统噪声的另一个因素就是等效源电阻。
After the bandwidth and temperature, the remaining factor in determining the system noise is the effective source resistance.
表2-3给出了典型的反馈安培计在各种测量范围内最小的源电阻推荐值。
Table 2-3 summarizes minimum recommended source resistance values for various measurement ranges for a typical feedback ammeter.
DUT的源电阻会影响反馈安培计的噪声性能。源电阻降低，安培计的噪声增益就增加。
The source resistance of the DUT will affect the noise performance of a feedback ammeter. As the source resistance is reduced, the noise gain of the ammeter will increase.
如图2 - 2所示，输入偏置电流(IBIAS)在源电阻(RS)上产生了误差电压。
As shown in Figure 2-2, the input bias current (IBIAS) develops an error voltage across the source resistance (RS).
噪声能够严重地影响灵敏的电流测量工作。本节讨论源电阻和源电容如何影响噪声的性能。
Noise can seriously affect sensitive current measurements. This section discusses how source resistance and source capacitance affect noise performance.
上述公式给出了降低约翰逊噪声的几种方法，即可以减小带宽、降低源的温度或者降低源电阻。
The previous equations suggest several means for reducing Johnson noise. It might be possible to reduce the bandwidth, the source temperature, or the source resistance.
虽然输入偏置电流是这种误差的常见来源，但是外电路产生的电流在源电阻上形成的电压降也能引起误差。
Although input bias current is a common source of this type of error, currents generated by external circuits can also result in errors due to voltage drops across the source resistance.
在测量高电阻源时要考虑的另一个问题是电压表的输入偏置电流。
Another consideration when measuring voltages from high resistance sources is the input bias current of the voltmeter.
而且，使用可调的电压源，还可以直接得到被测电阻对电压的依赖关系。
Also, with an adjustable voltage source, the voltage dependence of the resistance under test can be obtained directly.
跨接在电压源上的任何外部分流电阻都会使测量的电压衰减，如图2 - 3所示。
Any external shunt resistance across the voltage source will attenuate the measured voltage, as shown in Figure 2-3.
泄漏电流是由测量电路和附近的电压源之间的寄生电阻通路产生的。
Leakage currents are generated by stray resistance paths between the measurement circuit and nearby voltage sources.
如果使用分离的电流源和电压表来进行低电阻测量，则必须检查每台仪器的非欧姆接触情况。
If using a separate current source and voltmeter to make low resistance measurements, each instrument must be checked for non-ohmic contacts.
有些静电计和皮安计具有内置的电压源，能够自动地计算出未知电阻。
Some electrometers and picoammeters have voltage sources built into the instrument and automatically can calculate the unknown resistance.
注意，这种测量方法是两线电阻测量，而使用静电计电压表和外部电流源则可以进行四线测量。
Notice that this is a two-wire resistance measurement compared to using the electrometer voltmeter and external current source, which can make a four-wire measurement.
在将一个电压源切换至多个装置时，则可能必须补偿由于开关电阻引起的压降。
When switching a voltage source to multiple devices, it may become necessary to compensate for voltage drops due to switch resistance.
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.
然而，有的静电计和皮安计内部装有电压源，能够直接测量电阻。
Some electrometers and picoammeters, however, have a built-in voltage source and are capable of measuring the resistance directly.
介绍了含受控源单口网络的等效电阻的一种求法。
This paper introduces a new solution of equivalent resistance of one port net containing controlled source.
仪表的输入电阻应当远远大于源的内阻才能满足对测量准确度的要求。
The meter input resistance should be much higher than the source resistance.
在此方法中，恒压源(V)与未知电阻(R)和安培计(IM)相串联。
In this method, a constant voltage source (v) is placed in series with the unknown resistor (r) and an ammeter (IM).
典型的数字源表不像源-测量单元那样具有极高输入电阻或极低的弱电流测量能力。
The typical SourceMeter instrument doesn't have as high an input impedance or as low a current capability as a source-measure unit.
例如，如果希望的准确度为1%，那么表的输入电阻必须比源的电阻高100倍。
For example, if the desired accuracy is 1%, then the meter resistance must be more than 100 times the source resistance.
设计了一种高准确度无电阻的带隙基准电压源。
A high accuracy band-gap reference voltage without resistor is designed.
探索了用地层倾角、长源距声波、电阻率、三孔隙度及蚀变系数识别储集空间类型以及对储层分类的方法；
The methods to identify the types of reservoir by using such parameters as dipmeter, long space sonic, resistivity, porosity and alteration factor are studied.
最初的集成运算放大器的输出级是NPN电流源的NPN放射追随器或通过电阻下拉，如图1.6所示。
The earliest IC op amp OUTPUT stages were NPN emitter followers with NPN current sources or resistive pull-downs, as shown in Figure 1.6.
在图1 - 20所示的这种方法中，电流源产生的电流(I)流过未知电阻器(RX)。
In this method, shown in Figure 1-20, a current source generates current (I), which flows through the unknown resistor (RX).
在图1 - 20所示的这种方法中，电流源产生的电流(I)流过未知电阻器(RX)。
In this method, shown in Figure 1-20, a current source generates current (I), which flows through the unknown resistor (RX).
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