Table 2-1
Summary of measurement considerations
Considerations Description
See Model 6485 Instruction Manual, Appendix C or
Model 6487 Reference Manual, Appendix G for details.
Input bias current Offset current of Model 6485/6487 could affect low current
measurements.
Voltage burden Offset voltage of Model 6485/6487 could cause errors if it is high in
relation to the voltage of the measured circuit.
Noise Noise generated by source resistance and source capacitance.
See Appendix B for details.
Ground loops Multiple ground points can create error signals.
Triboelectric effects Charge currents generated in a cable by friction between a conductor
and the surrounding insulator (i.e., bending a triax cable).
Piezoelectric and stored
charge effects
Currents generated by mechanical stress on certain insulating
materials.
Electrochemical effects Currents generated by the formation of chemical batteries on a
circuit board caused by ionic contamination.
Humidity Reduces insulation resistance on PC boards and test connection
insulators.
Light Light sensitive components must be tested in a light-free
environment.
Electrostatic interference Charge induced by bringing a charged object near your test circuit.
Magnetic fields The presence of magnetic fields can generate EMF (voltage).
Electromagnetic Interference
(EMI)
EMI from external sources (i.e., radio and TV transmitters) can
affect sensitive measurements.
2-16 Connections Model 6485 and 6487 User’s Manual
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