Abstract: A heater is disclosed for use with pressure transducers. The disclosed heater includes a first heating element and a second heating element. The first heating element is characterized by a first electrical resistance. The second heating element is characterized by a second electrical resistance. In preferred embodiments, the first electrical resistance is different than the second electrical resistance. The disclosed heater can be used to accurately heat a pressure transducer to at least four different operating temperatures by selectively (a) connecting the first heating element to the transducer temperature control circuitry, (b) connecting the second heating element to the transducer temperature control circuitry, (c) connecting the first and second heating elements in series with the transducer temperature control circuitry, or (d) connecting the first and second heating elements in parallel with the transducer temperature control circuitry.

Abstract: Apparatus for soldering surface mounted devices to printed circuit boards utilizing a combination of forced convection and infrared radiation. Fans are disposed in each heating zone which force gas through a heating plate which heats the air, emits infrared radiation for heating of printed circuit boards, and establishes a flow pattern for the gas. Flows are controlled in each zone by selectively introducing unheated gas into each zone, and by selectively exhausting gas from each zone. The volume of gas introduced and exhausted from each zone can be controlled. Closures are provided in the return channels to the low pressure side of the fan for controlling the volume of gas recirculated from the conveyor. Flow is controlled such that cooler air is always introduced into the zones which have a lower temperature and is exhausted from zones which have higher temperatures.

Abstract: Apparatus for soldering surface mounted devices to printed circuit boards utilizing a combination of forced convection and infrared radiation. Fans are disposed in each heating zone which force gas through a heating plate which heats the air, emits infrared radiation for heating of printed circuit boards, and establishes a flow pattern for the gas. Flows are controlled in each zone by selectively introducing unheated gas into each zone, and by selectively exhausting gas from each zone. The volume of gas introduced and exhausted from each zone can be controlled. Closures are provided in the return channels to the low pressure side of the fan for controlling the volume of gas recirculated from the conveyor. Flow is controlled such that cooler air is always introduced into the zones which have a lower temperature and is exhausted from zones which have higher temperatures.