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A g r e At e r m e A s u r e o f c o n f i d e n c e




Introduction 2 Low Current Measurements 2 Measurement Circuit 2 Leakage Currents and Guarding 3 Noise and Source Resistance 3 Zero Drift 4 Generated

Currents 4 Overload Protection 6 AC Interference and Damping 6 Using a Coulombmeter to Measure Low Current 7 High Resistance Measurements 8 Constant-

Voltage Method 8 Constant-Current Method 8 Guarding 9 Settling Time 10 Low-I Application 11 High-R Application 12 Selector Guide 13 Glossary 14
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Introduction..................................................................2
Low Current Measurements
Measurement Circuit .................................................. 2
Leakage Currents and Guarding .......................... 3
Noise and Source Resistance ................................. 3

Low Current Measurements Zero Drift ........................................................................ 4
Generated Currents................................................... 4
Overload Protection .................................................. 6
HI AC Interference and Damping.............................. 6
Using a Coulombmeter to
Measurement Circuit Measure Low Current ..................................................... 7
Introduction The correct measurement circuit for making a current RS RM High Resistance Measurements
Testing and characterizing metallic materials, low measurement is shown in Figure 1. Ensure that the Constant-Voltage Method ...................................... 8
temperature superconductors, nanoscale materials, measurement instrument is at a low voltage point in the VB Constant-Current Method ...................................... 8
highly doped semiconductors, photo-diode dark circuit. This ensures that the instrument is less likely VS IM
Guarding ........................................................................ 9

currents, and electron beam currents from accelerating to be damaged by an over-voltage applied across the Settling Time ................................................................ 10

devices requires making current measurements at instrument. Also, when the instrument is near circuit LO
Low-I Application: Avalanche Photodiode
Reverse Bias Current Measurements...................... 11
nanoamp levels and below. Either the generated common, noise voltages tend to be lower. Thus, a better
High-R Application: Voltage Coefficient
current is low or very low power materials, such measurement can be obtained. DMM, Electrometer, SMU, Testing of High Ohmic Value Resistors ................. 12
or Picoammeter
as single-atomic-layer graphene, must operate with Current Source
Selector Guide ........................................................... 13
very low currents to minimize power dissipation VS VS