A fluid pressure responsive electric switch comprising: an elongated generally tubular base member having a longitudinal axis and having a sidewall extending between a first and a second end; a motion transfer guide member having a central bore mounted at the first end of the base member; a fluid pressure responsive sensor assembly, comprising a composite actuator member sandwiched between a disc housing member with a central aperture and a housing support member with a central aperture, the disc housing member, housing support member, and the composite actuator member being in alignment with the guide member, the sensor assembly and the base member being joined together; and an electric switch disposed within the base member and a motion transfer pin slidably mounted in the guide member and extending through the aperture in the housing support member between the composite actuator member and the electric switch, characterised by the disc housing member, housing support member, and the composite actuator member all having outer circular peripheral portions being welded together in a multi-pass operation to minimize localized annealing effects of the composite actuator member, said composite actuator member comprising a plurality of snap-acting disc members and a thermal adjustment member of a chosen low CTE material, the plurality of snap-acting disc members including at least one member of a chosen low coefficient of thermal expansion material and at least one member of a chosen high coefficient of thermal expansion material of higher CTE than the CTE of the low CTE material, the material of thermal adjustment member being of lower CTE than the CTE of the high CTE material. an elongated generally tubular base member having a longitudinal axis and having a sidewall extending between a first and a second end; a motion transfer guide member having a central bore mounted at the first end of the base member; a fluid pressure responsive sensor assembly, comprising a composite actuator member sandwiched between a disc housing member with a central aperture and a housing support member with a central aperture, the disc housing member, housing support member, and the composite actuator member being in alignment with the guide member, the sensor assembly and the base member being joined together; and an electric switch disposed within the base member and a motion transfer pin slidably mounted in the guide member and extending through the aperture in the housing support member between the composite actuator member and the electric switch, characterised by the disc housing member, housing support member, and the composite actuator member all having outer circular peripheral portions being welded together in a multi-pass operation to minimize localized annealing effects of the composite actuator member, said composite actuator member comprising a plurality of snap-acting disc members and a thermal adjustment member of a chosen low CTE material, the plurality of snap-acting disc members including at least one member of a chosen low coefficient of thermal expansion material and at least one member of a chosen high coefficient of thermal expansion material of higher CTE than the CTE of the low CTE material, the material of thermal adjustment member being of lower CTE than the CTE of the high CTE material.