Abstract: Apparatus compensating for "aperturing effects" produced when a sample holding aperture is incorporated in the sample beam of a conventional dual beam spectrophotometer to allow examination of very small size samples. Such effects usually take the form of undesired variations in the base line output of the spectrophotometer at wavelengths where the spectrophotometer slits open wider than the sample aperture in an attempt to produce a constant energy scan over a given spectrum. The apparatus comprises a second aperture optically equivalent to the sample aperture and located at a slit image point in a common beam portion of the spectrophotometer.

Abstract: A variable chart format system for a recorder with a chart print out, the system having a manually selectable switch for simultaneously controlling the abscissa and ordinate formatting independent of scale expansion circuitry normally associated with the abscissa and ordinate. The abscissa formatting is digital and operable in response to a programmable or variable clock, the output of which is selectively passed through a first set of abscissa formatting frequency dividers and then serially through one of a second set of abscissa scale expansion frequency dividers to drive a chart drive stepper motor.