Abstract: A proportional oven having two heaters mounted to a thermally conductive base stabilizes the temperature of a temperature sensitive crystal mounted on the thermally conductive base by adjusting the ratio of powers applied to the two heaters.

Abstract: A gas-controlled heat-pipe thermostat of high precision comprising a closed pipe interiorly covered with a capillary structure; a gas pressure regulation system containing control gas in communication with the interior of the pipe and a working fluid. The pipe defines first and second condensation zones and an intermediate evaporation zone. The working fluid within the pipe upon reaching the evaporation zone is vaporizable and dividable into two portions, each portion flowable to one of the first and second condensation zones after which it returns to the evaporation zone by way of the capillary structure for recycling. The control gas of the gas pressure regulation system forms a buffer zone. The positioning of the evaporation zone in relation to the second condensation zone resulting in the evaporation condensation cycle through the first of the condensation zones is separated from the control gas by the evaporation condensation cycle through the second condensation zone.

Abstract: An improved oven (10) for maintaining the junctions of a plurality of reference thermocouples at a common and contant temperature. The oven (10) is characterized by a cylindrical body (12) defining a heat sink having an axially extended cylindrical cavity (14), a singularized heating element comprising a unitary cylindrical heating element consisting of a resistence heating coil (20) wound about the surface of a metallic spool (18) having an axial bore (22) defined therein and seated in the cavity, an annular array of radially extended bores (30) defined in the cylindrical body (12) and a plurality of reference thermocouple junctions (32) seated in the bores in uniformly spaced relation with the heating element, and a temperature sensing device (28) seated in the axial bore for detecting temperature changes as they occur in the spool and circuit (46) for applying a voltage across the coil in response to detected drops in temperatures of the spool.

Abstract: Temperature regulating apparatus for the control of temperature within an enclosure including a temperature measuring circuit which measures the temperature within the enclosure and a semiconductor heating circuit for generating heat responsive to the temperature measuring circuit. The temperature measuring circuit includes a resistive bridge with a temperature sensitive element as one of its legs, the output of the bridge being coupled to an amplifier for developing a temperature signal which varies as a function of the temperature within the enclosure. The heating circuit includes a plurality of transistors having their respective collector-emitter paths coupled in series so that a heating current can flow through the collector-emitter paths of all of the transistors. One of the transistors, designated the control transistor, has its base coupled to the output of the amplifier for controlling the heating current by the temperature signal.

Abstract: A crystal oven for radio frequency control crystals includes a crystal socket board, mounted directly on one side of a printed circuit board. The crystal sockets extend through and are soldered to corresponding cyrstal socket terminals on the opposite side of the printed circuit board. A housing surrounds the crystal socket board and is attached to the printed circuit board. An oven temperature control circuit including a power transistor controls the amount of current flowing through a heating wire, which is wrapped around and mounted to the housing. The collector plate of the power transistor is mounted to a heat sink, which overlies the crystal socket terminals. Heat generated by the collector plate as a result of current through the power transistor is distributed across the heat sink and is transferred by convection to the crystal socket terminals to reduce the amount of heat transfer through the crystal socket terminals.

Abstract: Junctions of the signal leads from equipment monitoring sensors to conventional cable lines are made by forming reference junctions of the signal leads in shielded temperature controlled oxygen-free hardened copper slugs embedded in a beryllium oxide block. Sensors may readily be changed since the junctions of the signal leads in the copper slugs are made through removable plastic taper pins forming pressure contacts of the leads in recesses formed in the copper slugs. The universal reference junctions are particularly suited for making connections to the leads of sensors which are located in intense electrical fields.

Abstract: An oven having a thermistor controlled proportional heating system is compensated for ambient temperature variations by using a second thermistor sensing ambient temperature and connected in series with the control thermistor in an electrical bridge circuit. The control thermistor is mounted within the oven and substantially monitors the oven temperature while the ambient thermistor is located outside the oven and monitors ambient temperature. The electrical bridge circuit produces a temperature control error signal which is amplified and applied to a heater winding which is wrapped around the oven. The ambient thermistor produces a resistance variation in the electrical bridge circuit which modifies the temperature control signal such that a predetermined point inside the oven is held at a constant temperature regardless of any ambient temperature changes.

Abstract: A transistor with its base-emitter bias controlled by a positive temperature coefficient thermistor provides a controlled heat source for maintaining precise temperature within a small oven which is used to contain and provide a stable temperature for temperature sensitive elements of external circuits.

Abstract: The disclosure describes improved apparatus for protecting the motor of a refrigerant compressor. The apparatus includes fusible links and a magnetic contactor connected in series between a source of three-phase AC voltage and the compressor motor. If the contactor fails in the closed position, a relay energizes resistors which heat the links. In response to the heat, the links are switched to an open circuit condition that disconnects the compressor from the source of AC voltage.