Very nice device, with that interesting proprietary low-leakage connector. Is there a standard cable to connect with the Keysight B9285A triax input?
(For my less-sensitive requirements, I rely on a Keithley K261 "picoampere current source" to work with my Keithley 610C analog and 616 digital electrometers. It is merely a Kelvin-Varley divider driving a set of the usual glass-encased Victoreen carbon resistors mounted on a rotary switch. The most sensitive range is 0 to 9.99 V through a 1 x 1012 ohm resistor.)
Thanks!
This device doesn't have standard cable for connect to B2985A and similar. Need to DIY.
For currents >=1E-9A this device use network of precision microwire resistors and DAC.
For currents <1E-9A this device use capacitors and DAC that generate ramp voltage.
The use of differentiating capacitors to generate ultra-low currents in this calibrator has solved 2 problems at once.
1. Lack of stable ultra-high resistance resistors suitable for the high precise generation of such currents.
2. Get rid the thermal noise of the resistors.
The amplifier of V7-45 for the same reasons also using integrating capacitor in their feedback. - Full eliminate current noise from resistors. And more precise measurement, due the capacitor is more stable than ultra high resistance resistors (time and temperature).
Photos: output connector with sapphire insulator on differentiator №2. This differentiator used to generate output currents from 1E-14A to 1E-16A. And connector with amber insulator on one of kit's cable.