Measuring apparatus

Abstract

A zero-balancing arrangement incorporated into a pocket-type apparatus, which pocket-type apparatus is capable of being handled and operated by one hand of the user. The apparatus includes at least one battery to supply energy to a lamp which is used as a light source. A cuvet containing a liquid to be measured is placed into the path of a measuring light beam through an opening in the casing of the apparatus. A wedge-shaped filter is movable in the path of a second light beam by manual operation of a setting wheel. A measuring scale provided on the setting wheel can be inspected through a viewing window and the setting wheel can be adjustable relative to a mark fixedly located on the casing of the light beam paths provided in the apparatus, the first one travels through the liquid in the cuvet to a first photoelectric sensing device and the second light beam path travels unobstructed to a second photoelectric light sensing device. An electronic regulating system is provided to adjust the voltage at the inputs to a differential amplifier and to adjust the output of the differential amplifier to a zero value so that a light meter reading is initially adjusted to a zero value prior to a measuring of a particular liquid in the cuvet.