Subpicoampere current source based on a digital-to-analog converter
A current source based on a voltage ramp generated by a 16-bit digital-to-analog converter and a differentiating capacitor has been developed in MIKES. The system is suitable for generating currents from 1 fA to 100 pA. Standard deviation of average dU/dt:s of 70 ramps during an overnight measurement is as low as 1 ppm.
New Capability for Generating and Measuring Small DC Currents at NPL
This paper describes two systems recently developed at the National Physical Laboratory (NPL), Teddington, U.K., for the generation and measurement of dc currents in the range 100 fA to 1 nA. Both systems are based on the capacitor charging technique. One system generates known currents, and constitutes a new reference at NPL. The other was designed to meet the traceability requirements of the Ionizing Radiation sections of NPL and combines commercially available instrumentation and standards to produce a reliable stand-alone system for measuring small currents
An accurate, self-checking digital teraohmmeter
We describe a new digital teraohmmeter achieving state-of-the-art linearity and long-term stability through the application of automatic self-checking circuits and routines. To ensure its voltage-independence up to 1000 V and <100 ppm linearity in measuring 10/sup 5/ to 10/sup 15/ /spl Omega/ (at /spl ges/1 pA), internal scaling and timing circuits have been upgraded for higher speed and better performance.<<ETX>>