New electronics for the Beckman LB-1 carbon dioxide analyzer

Abstract

This paper describes an amplifier and linearizer for the Beckman LB-1 carbon dioxide analyzer head. All electronics are solid state and DC regulated in contrast to the original LB-1 amplifier which was of vacuum tube design and AC regulated largely by means of a voltage stabilizer transformer. A new detection principle is adopted which reduces drift due to mechanical imperfections of the chopper motor (e.g., bearing drag), but also offers the advantage that the phasing of the chopper blades is no longer necessary. Furthermore, the amplifier with a digital readout and an end-tidal hold circuit can be built for less than $500 and is plug compatible with the LB-1 head.