Abstract: A control system for controlling a closed-loop refrigeration system having multiple parallel commonly piped compressors is disclosed. Various combinations of compressors define the compressor capacity stages of the system. The disclosed control system responds to a system parameter, such as the suction line pressure or the temperature of an area to be cooled by an evaporator of the refrigeration system, to control the selection of the minimum system compressor capacity necessary to maintain the temperature of the area to be cooled to the lowest temperature. Control of the compressor capacity is effected by the sensed system parameter by generating an operating range defined from an upper to a lower operating limit. Operations above or below this range determines whether an increase or decrease, respectively, in compressor capacity needs to be made.

Abstract: A vaporizing humidifier includes a portion for providing stepwise increases and decreases in vapor output capacity in response to the duration of a vapor demand signal, for matching the vapor output to the demand therefore.

Abstract: A variable speed integrator for controlling the response time of a valve which regulates the amount of coolant flowing to a heat exchanger so as to control the temperature of the cooled substance output from the exchanger. The temperature of the cooled substance is sensed and compared to a set point temperature to determine an error temperature representing the difference between the sensed and set point temperatures. The error temperature is integrated by the variable speed integrator, the output of which is used to drive the valve into position. The control system monitors the rate of change of the sensed temperature to determine a low system gain. When the rate of temperature change indicates a low gain system, the gain of the integrator is increased to decrease the response time of the valve.

Abstract: A control method uses a room thermostat for generating an output signal representative of an energy demand and an energy source which can be cyclically switched on and off and includes the steps of determining within a switching cycle of the energy source the actual switch on period, comparing the actual switch on period with an adjustable desired switch on period within the cycle to produce a control signal representative of the energy demand and controlling the energy source in accordance with the control signal.

Abstract: A temperature control system for a building is disclosed utilizing a central demand limit controller. The system includes a number of control modules or thermostats that have both proportional error and integral error functions. The integral error is reset at intervals by an interstage differential to drop single stages of air conditioning. This reduces demand until the maximum allowed demand is met. The integral error function is a timed function and the stages return in a random manner to restore setpoint temperature.

Abstract: A system for stabilizing the temperature of a radiation detector assembly includes a heat pipe device which generally encloses the radiation detector assembly and absorbs the ambient heat of the radiation detector assembly. A temperature sensor senses the ambient temperature in the heat pipe device and provides a constant current signal representative of the sensed temperature. A heating cooling device controls the ambient temperature within the heat pipe device in accordance with a constant current control signal. Apparatus located at a substantial distance from the radiation detector assembly and connected to the temperature sensor and the heating cooling device provides the constant current control signal to the heating cooling device in accordance with the constant current temperature signal from the temperature sensor so as to control the temperature of the radiation detector assembly.

Abstract: An electronic control for positioning the damper in the air supply duct of a variable air volume system having a motor to open and close the damper, a thermostat circuit sensing temperature in a conditioned space and developing a voltage signal indicative of the temperature in the space relative to the thermostat setting, an electronic air flow sensing circuit sensing air flow into the conditioned space and developing a voltage signal indicative of air velocity, a circuit processes both signals and applies the difference between them to an electronic variable timer which effectively varies the motor speed (by varying the motor duty cycle) so said damper is moved slower as equilibrium between the space temperature and the set point of the thermostat is approached. The same voltage signals are fed into a logic circuit to determine the direction of motor rotation to determine whether the damper opens or closes.

Abstract: A method for controlling a temperature of an object to be cooled or heated by a cooling/heating apparatus is improved in that a controllable temperature range of the object is divided into three or more sections and in the respective temperature sections, the temperature of the object is controlled through methods suitable for the respective temperature sections.

Abstract: A diffusion pump is operated by controlling the rate at which vapor is evaporated from a pool in response to an indication of the effectiveness of a fluid in cooling a condensation surface for the vapor as derived by sensors for the temperatures of the pool and along a temperature gradient from the pool to a cooling coil for the condensation surface. When the sensors indicate that the vapor is not effectively cooling the surface, liquid is vaporized from the pool, but at a slower rate than when the fluid is effective in cooling the surface. To increase the life of a brass strap on the temperature gradient, opposite ends of the strap are connected to a cooling coil for the condensation surface and a stainless steel block connected to a well in which is located an electric heater for vaporizing the oil from the pool.

Abstract: The circulation of heat transfer fluid through the low temperature heat exchanger in the temperature control system of a freeze dryer is selectively increased when the temperature of heat being applied to the product shelf assembly in the freeze dryer exceeds the desired temperature. Preferably, a servo-controlled mixing valve selectively bypasses the low temperature heat exchanger so that the rate of cooling is very precisely adjusted without requiring the heat exchanger refrigeration unit to be cycled on and off. Since the refrigeration unit operates continuously, the reliability and operating lifetime of the refrigeration unit is increased. Moreover, the heat exchanger temperature is maintained at a minimum value. Preferably, the servo-control for the mixing valve includes a digitally controlled stepping motor and the adjustment of the mixing valve is sensed by a linear voltage displacement transducer. To prevent short cycling and oscillation, a dead band is introduced in the servo-control loop.

Abstract: A refrigeration system is disclosed which may have multiple compression and condenser stages, in which an electronic refrigerant expansion valve is controlled by the digital output of a microcomputer which adjust the expansion valve in response to a valve change signal which is a function of a fraction of the deviation of the sensed refrigerant superheat from a desired superheat added to a multiple of the computed rate of change of the refrigerant superheat.

Abstract: A boiler control utilizing a pressure sensor is provided that operates the system in the low fire mode if the load is light and can be satisfied in that mode. If the low fire operation is inadequate to hold the load, and the pressure drops, the boiler is then operated in a modulating mode which includes a high fire limit.

Abstract: A boiler control utilizing a pressure sensor is provided that operates the system in the low fire mode if the load is light, and can be satisfied in that mode. If the low fire operation is inadequate to hold the load and the pressure drops, the boiler is then operated in a modulating mode which includes a high fire limit. This is accomplished by sensing the variation of a pressure responsive means and by providing a burner control system that monitors that pressure responsive means.

Abstract: A thermostat uses a source of a signal representing anticipation heat which is transmitted to a circuit to be combined with a signal from a temperature sensing element with a first time constant or delay when the thermostat is "ON", i.e., controlling a heat source to supply heat to a heat receiver and with a different time constant or delay when the thermostat is "OFF", i.e., controlling the heat source to interrupt the supply of heat to the heat receiver.

Abstract: A steady state thermostat is disclosed which employs a magnetic flux coupling technique to obtain a greater stability in its operation, resulting in a significant reduction in fuel costs. The thermostat includes a temperature sensor operated arm and a temperature setting arm pivotally mounted on a common base pivot. A first magnetic field source is mounted on the first end of the sensor arm coincident with a first axis and a second magnetic field source is mounted on the second end of the sensor arm coincident with a second axis. A first magnetic field sensor is mounted on the first end of the setting arm coincident with the first axis and adapted for proximate positioning with respect to the first magnetic field source when the selected orientation of the setting arm corresponds to the desired ambient temperature being higher in magnitude than the existing ambient temperature.

Abstract: A control circuit for a liquid fuel combustion apparatus which employs a differential amplifier and square-wave generator to maintain a strong constant combustion in the burner until the differential amplifier senses that room temperature has approached a preselected target temperature, at which point the differential amplifier operates to alter the square-wave generator output to gradually reduce the combustion rate in an inverse proportion to room temperature as the target temperature is being reached. The differential amplifier subsequentially controls the square-wave generator in a manner which causes fuel to be available at a rate necessary and sufficient for maintaining the target temperature.

Abstract: A gas flow rate control system designed to control the gas flow rate by continuously controlling the opening of an electromagnetic valve, wherein the magnetic hysteresis of a plunger and a yoke which are magnetic material forming the magnetic circuit is removed by alternately passing current pulses through two energizing coils, so as to continuously reverse the direction of magnetization of the magnetic circuit and wherein the static friction between the plunger and the yoke is removed by oscillating the plunger.

Abstract: By means of a moveable insulating member that has two electrically conductive areas that are separated by a nonconductive area it is possible to build a mechanically controlled electronic thermostat. The temperature sensing is accomplished by a temperature responsive means that moves generally parallel to the conductive area, and functions as a pair of differentially energized variable capacitors that drive an electronic circuit when any unbalance occurs. This unbalance is indicative of a disagreement of the set temperature with the control temperature.

Abstract: A sensor control device for controlling the operation of a device such as an air blower, including a sensor capable of sensing a change in the environment from a predetermined level and providing a signal corresponding to the change and a logic means capable of receiving the signal and based upon this signal control the operation of the blower device in such a manner that its operation is in proportion to the change in the environment while inhibiting small changes from affecting the operation of the blower. The sensor device is particularly advantageous in controlling the amount of circulation provided by a blower device interposed between a thermal collector and a building so as to provide the circulation of thermal energy therebetween.

Abstract: A condition control system adapted to supply a working fluid that has been modified by transferring energy to or from the working fluid is disclosed wherein a minimum energy loss is accomplished in operating the control system. The control system adjusts the setpoint of the system in response to parameters measured around the system and further provides for a minimum on/off cycling of the system in the event that the system is applied to a device which alters the working fluid between a fixed lower rate and an upper rate as would be typical in a burner-boiler configuration.

Abstract: In a process in which a feedstock is provided through a desalting unit prior to introduction into a fractional distillation column, the feed stream flowing to the desalting unit is split and passed through multiple heat exchangers. Method and apparatus is provided for maintaining a desired effluent flow rate out of the desalting unit and for maintaining the temperatures of the split feed streams substantially equal. After passing through the desalting unit the feed stream may again be split and passed through multiple heat exchangers prior to introduction of the feed stream into the fractional distillation column. Method and apparatus is also provided for maintaining the temperature of the split feed streams provided from the desalting unit substantially equal.

Abstract: A two-stage circuit for controlling all operational functions of a reversible air cycle heat pump unit, including room thermostat functions and defrosting functions. All user controllable functions are controlled via a remotely locatable thermostat-like control unit mounted on an inside wall of the room separate from the heat pump unit, and connected to the heat pump unit with only five conductors. A number of desirable functions and features are provided. For example, for optimum energy usage the control provides two stages in both heating and cooling modes of operation, with almost constant temperature differential between the two stages regardless of temperature setting, and almost constant hysteresis for each stage. To facilitate compliance with Government-imposed regulations where applicable, heating and cooling limits are independently adjustable without any modification whatsoever for use in those public buildings where heating and cooling must be limited.

Abstract: An air conditioner system for sensing and controlling the temperature in the compartment of an automotive vehicle to an established desired temperature includes an over-correction means whereby the vehicle compartment temperature is temporarily increased to exceed the desired temperature and the temperature rise is terminated after the sensed temperature has attained or nearly attained the desired temperature. When the sensed temperature rises so that the difference between it and the desired temperature exceeds a reference value, the corresponding correction signal is generated and correction is applied repeatedly so as to make the difference less than the reference value and thereby to attain the desired compartment temperature.

Abstract: An electronic temperature control having a temperature sensor (10) and a user-adjustable temperature range control (12). A difference amplifier (14) amplifies the difference between the signals from the temperature sensor and range control. A hysteresis comparator (16) then accepts the signal from the difference amplifier and uses it to control a transistor relay driver (18), which in turn controls the clutch coil (20) of the air conditioning system controlled by the temperature control. The transistor relay driver is disabled by an evaporator fan sensor (22) to avoid freeze-up of the evaporator when the fan is turned off. Since auto air conditioning systems rob the car's engine of power, an acceleration cut-out (24) is provided to disable the transistor relay driver when other power demands on the car's engine are great, such as on hard acceleration.

Abstract: A pressure control system for an air distribution system which includes a supply blower (10), a distribution duct network (20) and a plurality of air outlets (22a, 22b), includes a plurality of pressure sensors (25a, 25n) positioned at various points in the air ducts to measure pressure therein. Controls are provided for selecting the lowest of the sensed pressures (42) and the low pressure signal becomes one input to a variable dead band controller (44). Another input is an adjustment (45) for commanding the desired system pressure. The controller compares the pressure to a dead band threshold established about the set point and delivers appropriate signals to an actuator (31) which operates through a linkage (32) to control the inlet vortex vanes (33) and hence the air flow of the supply blower. A wide dead band is used to avoid hunting of the system, but when a response is required a narrow dead band is used to ensure that the system drives to the set point.

Abstract: The illustrated embodiment is electronic. It includes circuitry for simulating heat anticipation so that in operation, the temperature of the room being heated or cooled does not exhibit excessive overshoot. A signal is generated representative of a desired set point, and another signal is generated representative of room temperature. An output signal, derived from a comparison circuit, is either ON or OFF. An integrator is reset each time the output signal is switched and generates a ramp voltage of increasing magnitude and having a polarity tending to reverse the state of the comparison circuit. The comparison circuit generates an ON signal when the set point signal is greater than the combined temperature and ramp signals; and it generates an OFF signal when the set point signal is less than the combined signals. The comparison circuit latches up once it has switched to avoid hunting or chatter.

Abstract: A temperature control is disclosed for a variable volume air conditioning system of the type wherein electric motor-operated air valve means are provided for varying the volume of relatively warm or relatively cool conditioned air supplied to a conditioned zone. The control includes zone thermostat means for sensing the temperature within a conditioned zone, determining the deviation between a set-point temperature and the zone temperature, and for producing an electrical error signal having a magnitude which varies in a predetermined relationship with respect to said deviation in temperature. Valve motor control circuit means receive the error signal and are operative to energize electric motor-operated air valve means in response thereto so as to vary the volume of conditioned air being supplied to said conditioned zone in a sense to restore the zone temperature to the set-point temperature.

Abstract: A time proportional control means, shown as a temperature control system, utilizes an expanded time constant arrangement with a unidirectional type of digital counter. The control system also utilizes a pulse generating means that is linked to the set point control for the system. Any substantial change of the set point causes the pulse generating means to generate pulses that are used by a pulse responsive circuit to insure that the counter for the system is adjusted to cause the output of the system to correspond with the new set point position.

Abstract: An electrical circuit having three states depending upon the magnitude of an electrical signal coupled, in operation, to an input thereof, the circuit having a first stable state when the said magnitude is less than a first, predetermined value, a second, stable state when the said magnitude is greater than a second, predetermined value higher than the first said predetermined value, and a third, unstable state when said magnitude is equal to or between said first and second predetermined values. In a development of the invention, the circuit is incorporated in a control apparatus for a ducted, warm-air, central-heating system in which the gas supply to a burner is supplied continuously when the temperature of a space to be heated is below a predetermined temperature, is cut-off when the temperature of the space is above another, higher predetermined temperature, and is switched on and off at a rate dependent upon the magnitude of the temperature when it is equal to or between the two values.

Abstract: A novel control circuit for heating and heating/cooling systems wherein in a heating mode the circuit controls a valve means comprising a main valve and a modulating valve through which gas is supplied to a burner. The main valve is a normally closed, solenoid-actuated type which opens when its coil is energized, and energization of its solenoid is controlled by a pair of normally open relay contacts connected in series. One of the contacts closes when the temperature in the space being heated drops below a preset temperature. The other contact remains closed so long as the temperature in the space being heated remains below a maximum limit. In a heating/cooling system the circuit is selectively operatively coupled with the valve means and a refrigeration unit. When heating is selected, the circuit operates as mentioned above. In cooling, a cooling solenoid of the refrigeration unit is energized when the temperature in the space being cooled rises above a preset temperature.

Abstract: A proportional plus integral controller connectable in a conventional proportional control loop of a process control system is selectively operable in a proportional only mode or a proportional plus integral mode in accordance with the positioning of a mode select switch and exhibits substantially bumpless forward transfer from proportional only to proportional plus integral operating modes.

Abstract: An anti-reset windup proportional plus integral controller connectable in a proportional control loop of a process control system includes a proportional amplifier circuit and an integrating amplifier circuit responsive to a command signal to provide proportional and integral signals, respectively, which are summed by a summing amplifier to provide a modified command signal having a proportional and an integral component. A signal comparator means compares the modified command with a pair of reference signals which define an output range for said summing amplifier and disables the integrating amplifier circuit, permitting the integrating amplifier circuit to unwind whenever the modified command signal is not within the output range.