Precision Continuous Current Integrator

Abstract

An all-electronic precision current integrator for use with a charged particle accelerator has been developed which eliminates the substantial deadtime normally associated with multicycle current integrators utilizing relays as their basic switching elements. Integration is accomplished in the conventional fashion of charging a precision condenser with the current to be integrated, electronically noting the completion of a predetermined voltage excursion and then returning the condenser to its initial charge state for repetition of the cycle. A unique feature of this integrator is the return of the integrating condenser to its initial charge state through the transfer of a precise amount of negative charge to the condenser by an all-electronic charge transfer circuit. Integration continues during the charge transfer with no interruption and with no effect on the precision of integration. An electronic counter circuit interrupts the integration at the end of a preset number of cycles and gates off any associated equipment. Current range is approximately 1–500 μa. Accuracy at low currents is limited primarily by a total circuit leakage current of the order of 1.5×10−9 amp. At higher currents, electrometer and other circuit instabilities limit accuracy to slightly better than 0.01%.