Linear current=to-frequency converter for very small currents

摘要

A linear current/frequency converter for the measurement of very small currents has an amplifier (1) and feedback capacitor (2) which form the input stage of a recycling integrator triggered by the comparator (5). During a pre-determn. interval controlled by the quartz timer module (6,7) operating as a D-flip-flop a pulsed current source is activated. The source comprises a LED (9) of stipulated radiation wavelength and a fibre-optic link (10) to a photodiode detector (11) whose signals are fed back to complete the current balance loop.