A THICK-FILM ELECTROCHEMICAL INSTRUMENT

A miniature electrochemical sensor fabricated as a printed thick-film electrode assembly has been interfaced to a thick-film hybrid circuit potentiostat and voltage ramp generator in order to produce a portable instrument for the analysis of trace elements in water. The electrode assembly consists of an array of 200-mu-m square gold contacts in a planar construction with a silver/silver chloride reference electrode printed and fired onto an alumina substrate. The electrode assembly is interfaced via a thick-film hybrid circuit potentiostat fabricated as a 28 pin dual in-line package (DIP). The potentiostat in turn is controlled by a thick-film hybrid circuit voltage ramp generator, also fabricated as a 28 pin DIP. The use of thick-film hybrid circuit modules in the construction of the instrument reduces the susceptibility to extraneous noise sources. The high level of integration and resulting miniaturization achieved by the electronic circuitry enables the complete instrumentation to be contained in a compact, rugged and hence highly portable housing utilizing a small battery as the power source. User-configurable parameters include the sweep rate, polarity and range of the potential applied to the electrode assembly, together with the amplification level of the potentiostat output signal. In this way it is possible to use the instrument for a variety of measurements on the oxidation and reduction of trace elements in water. The output signals of the instrument are suitable for direct connection to a chart recorder for the production of voltammograms. Initial characterization of the complete instrument has included the measurement of dissolved oxygen concentrations in water.