While these new instruments perform the functions of a bridge, they lack a null function, instead successively measuring the voltage across the unknown resistor and the voltage across a standard resistor carrying the same current, and then dividing the results. Four helpful features available in today's instruments include swept parameter measurement capability, menu programming, test data collection, and setup storage. Swept parameter measurement provides values over a user-specified frequency range and delivers the information in graphical or tabular format via the display or printer. Menu programming allows operators to access test conditions with the touch of a button. Test data collection allows test results to be stored automatically on an internal diskette drive or transferred to a PC for further analysis.
Setup storage allows operators to store commonly used test routines.
However, care must still be exercised to ensure reliable results. Especially important for surface-mount manufacturing is the need for careful handling of small parts. The size of these devices often makes it difficult to obtain good electrical contact. One of the most useful tools is the Kelvin clip cable, which allows four-terminal connections to be made to passive components. It is especially useful for testing low impedances encountered with components such as electrolytic capacitors and inductors.