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John Fluke Mfg. Co., Inc.

John M Redfield, Jr

Bryan L Sparrowhawk

Steven T Mydynski

Alfred T Volberding

Easily removable conformable coatings having a controlled thickness with a predetermined minimum value are obtained by the application of a composition comprising a mixture of a viscous carrier material and small particles of a second material by any known method. When both the carrier material and the particulate material mixed therewith are selected to have high dielectric constants, the mixture may be used to obtain coatings suitable for protection of circuit boards supporting high impedance electrical circuits. A mixture of a commercially available grease, e.g., Amoco RYKON (TM), with glass microspheres comprising up to 50% of the volume and preferably in the size range 3-5 mils, provides excellent dielectric conformal coatings for high impedance circuit boards. By contrast, by selecting both the viscous carrier material and the particulate matter mixed therein to have high conductivity, electrically conductive coatings for particularized users may likewise be obtained according to this invention.

Removable controlled thickness conformal coating

In a temperature measurement system using a thermocouple connected to a pair of circuit wires coupled to a voltmeter for providing an output reading, an isothermal block (48) formed of alumina ceramic contains a series of openings (58-66) in linear juxtaposition. Metal connectors (68) located in two of the openings to interconnect the thermocouple and printed circuit wires of a circuit board (52) establish a reference junction. A temperature sensor (50), preferably a transistor, in a third opening measures the temperature of the isothermal block (48) to compensate the output reading for error created by the reference junction. The connectors (68) are in resilient contact with the interior wall of the isothermal block (48) to maintain good heat conductivity between the connectors and the temperature sensor (50). Portions of the connectors (68) extending outside the isothermal block (48) retain the isothermal block (48) to the circuit board (52).

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Seattle, WA, United States of America

John M Redfield, Jr