A computer-controlled multi-electrode switch

A computer-actuated switch was built to control, simultaneously, two automatic titration assemblies each consisting of an electrode pair and a burette, and using only one measuring device. This switch is modular, simple and versatile allowing easy adaptation and expansion; apart from its application in multiple-titration systems, this device can also be used for standard addition analysis and multi-component analysis using ion-selective electrodes (ISE). The repeatability as well as the accuracy of the measurements made with this switch were ensured using high-quality relays, and very high electrical insulation, attained through the use of two separate printed circuit boards (pcb) of good quality and careful design of these pcbs. This low-cost multi-electrode switch is controlled through the parallel port of a PC that collects the data via an inexpensive 12-bit ADC board (8-bit ISA type), and is easily programmable in any high-level language. This type of device allows the collection of a large amount of data in relatively short periods, which can be analysed later allowing the choice of the best compromise of time versus accuracy for the study of any particular system.