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.
Generation of Reference DC Currents at 1 nA Level With the Capacitance-Charging Method
The capacitance-charging method is a well-established and handy technique for the generation of dc current in the 100 pA range or lower. This method involves a capacitance standard and a sampling voltmeter, highly stable devices easy to calibrate, and it is robust and insensitive to the voltage burden of the instrument being calibrated. In this paper, we propose a range extender amplifier, which can be employed as a plug-in component in existing calibration setups, and allows the generation of currents in the 1 nA range. The extender has been employed in the Istituto Nazionale di Ricerca Metrologica setup and validated with two comparisons at 100 pA and 1 nA current levels. The calibration accuracy achieved on a top-class instrument is 5 × 10-5 at 1 nA.
Problems of a centralised department in a decentralised mental hospital.
Abstract This paper deals with some of the issues and problems which arose in a state mental hospital, when in the course of becoming a more community-oriented facility, the hospital decentralized its clinical structure into geographically-based treatment units while retaining a centralized nursing department administration. The effects of unitization and a subsequent attempt to reoganize the nursing department on both the character of professional roles and the integration of parts of the hospital are discussed within the context of an open-systems conceptual model of hospital organization.