Material-testing instruments have key changes that boost engineering insight

Low-current ammeters and electrometers — key instruments today for gaining insight into the electronic properties of new materials such as carbon nanotubes, advanced polymers, and novel insulators — have not undergone a major upgrade in decades. Considering their role in such activities, it is fitting that among the first new instruments to be introduced by Keysight Technologies (formerly the electronic measurement business of Agilent Technologies) are the B2980A Series femto/picoammeters and electrometers.

These instruments bring to market many features that engineers and researchers working with advanced materials have wanted. For one, they are the first graphical picoammeters and electrometers, about which more will be said later. They are also the first to be able to effectively measure attoamps and exaohms: specifically, down to 10 aA (or 0.01 femtoamps, which is 0.01 x 10^-15 A) and up to 0.01 EΩ (or 10 petaohms, which is 10 x 10¹⁵ Ω). Further, they provide battery operation, which frees measurements from any possible power-line contamination, which can easily hide a small but significant electrical signal.

Along with operating ranges from 2 pA to 20 mA and an internal 1,000-V source, the 6½-digit meters also provide graphical readings that can greatly simplify analysis. For instance, their time-domain view — in effect, a scope trace — makes it easy to capture transient signal effects, as well as select desired measurement data from a signal. The instruments’ sampling rate is 100 kHz (10 µs) and their data buffer can hold up to 100,000 points.

But perhaps the most useful graphical display is the real-time histogram. This allows users to get a quick statistical analysis of measurement data. Previously, this was only possible by moving data to an external PC, whereas the instrument’s display is continuously updated on a real-time basis. The real-time analysis makes it easy to spot trends during measurements, and when the last few digits in a reading are unstable, the histogram rapidly tells the true distribution of readings, helping quickly debug measurements. This is a significant performance improvement, especially when considering that instrument prices begin at $6,200.

And there’s more. For highly sensitive measurements, setting up the appropriate cabling and equipment connections can be very difficult, and that complexity can lead to incorrect measurements. Conventional picoammeters and electrometers don’t address this issue, but the B2980A Series has an optional test-setup-integrity function and dedicated accessories. The combo is designed to easily isolate causes of noise and thus help ensure maximum measurement accuracy.