Abstract: An electrochemical sensor assembly which allows a solution to make contact with an active sensing area of a sensor, while constraining the solution such that the fluid does not contact the sensor electronics and a method for fabricating such a sensor assembly. A sensor assembly is fabricated in accordance with a simple process, including: fabricating a master pattern which matches the external profile of an epoxy shell which will encapsulate a substrate upon which the sensors are mounted; forming a flexible tool (or mold) which conforms to the general profile of the master pattern; placing sensors together with any other desired electronic circuitry on a substrate (such as a printed circuit board or a ceramic pad to form a "hybrid"); pressing a number of electrical contact points on the hybrid and the active sensing area of each sensor on the substrate into contact with flexible protrusions of the flexible tool; and potting the hybrid.

Abstract: A method and apparatus for rapidly measuring chemical properties of a solution using a plurality of devices having relatively long thermal time constants selectively coupled to a control means. Current I.sub.d flows through only one device at a time. A timing logic control circuit controls the timing of the drain switch and, if present, the reference switch. The output of the multiplexing circuit is sampled a precise amount of time after each device begins conducting current. The temperature at the sample time is a constant. The characteristics of the solution in which the device is immersed is the only variable in the operation of the device (i.e., I.sub.d, and V.sub.ds are held constant). By sampling the output a predetermined amount of time after the device has been turned on, the temperature rise is controlled.