Abstract: An electrometer (20) for measuring an unknown DC potential finds particular utility in applications requiring a high input resistance and minimal current drain during measurement. The electrometer (20) employs a circuit containing a sampling diode (D1) and capacitor (C1). Prior to a measurement being taken, the capacitor (C1) is charged to a common-mode voltage and the diode (D1) is reverse biased to a potential approximating the unknown potential of the voltage source (30) to be measured. A switch (S1) is employed to momentarily cause current flow through the capacitor (C1) and to forward bias the diode (D1). The unknown potential is calculated from potentials associated with the sampling diode (D1) and the capacitor (C1). The calculation involves sampling the potential of the capacitor (C1) at precisely determined time delays.

Abstract: A shelf assembly for a storage locker having a plurality of upright rails locatable in the corners of the locker. A plurality of generally horizontal shelves are releasably mounted on the rails. Each shelf has first and second shelf members having cooperating guides which allow lateral expansion of the shelves to permit the shelf assembly to be used with different sized lockers. A releasable fastener holds the shelf members in their adjusted positions.