Abstract: A pressure sensor for accurate readings of low pressures utilizes an ultrasonic transmitter which sends a signal to a movable diaphragm via a waveguide. Pressure changes across the diaphragm causes changes in the signal path length from transmitter to receiver which are translated into pressure readings via electronic circuitry employing phase comparator circuitry. The received signal is split into two signals one of which is shifted in phase. A temperature responsive controller selects which received signal is used in a comparison with the transmitted signal thus greatly extending the temperature range over which the sensor operates. The use of an ultrasonic waveguide with a length of at least twice the frequency of the transmitted signal coupled to the transmitter eliminates echoes and reflections and provides for enhanced accuracy in reading even very low pressures.

Abstract: An improved monitoring and control system for a heating, ventilating and air conditioning (HVAC) unit which provides zone control in plural zones in which each zone includes a thermostat which controls a damper for its zone. One thermostat is selected and programmed to function as a monitor or master thermostat for selective actuation of the HVAC unit as well as controlling its zone damper. The other thermostats are programmed to function as slave thermostats and are interfaced with the master thermostat thereby allowing for independent zonal control in a multiple zone system which uses a single zone HVAC unit. The master thermostat may also receive control signals and data from higher intelligence such as a computer. Each thermostat is microcomputer-controlled with provision for both local and manufacturer programming via supplemental memory devices. The master thermostat contains a real time clock for time-basing the entire system with attendant advantages.

Abstract: A microcomputer-controlled thermostat for use in monitoring and controlling a single zone HVAC system which provides conditioned air to one or more zones. The thermostat can be programmed and used either as a monitor thermostat to control the HVAC unit alone and/or to control the HVAC unit and its damper in a multiple zone mode. The thermostat is also programmed as a slave thermostat in a master-slave relationship with a monitor thermostat. The microcomputer memory is supplemented with additional ROM containing control algorithms for use in system operation.

Abstract: A microcomputer-controlled thermostat for use in monitoring and controlling a single zone HVAC system which provides conditioned air to one or more zones. The thermostat can be programmed and used either as a monitor thermostat to control the HVAC unit alone and/or to control the HVAC unit and its damper in a multiple zone mode. The thermostat is also programmed as a slave thermostat in a master-slave relationship with a monitor thermostat. The microcomputer memory is supplemented with additional ROM containing control algorithms for use in system operation. Logic circuitry is used to recognize commands as being for operation of the HVAC unit, the operation of the damper, or selection of which systems sensors are to be enabled. A real time clock circuit in the monitor thermostat is used to supply data for time-based system operation.

Abstract: A microcomputer-controlled bypass controller for use in maintaining a minimum airflow through a heating/cooling unit and limit the static pressure in the supply air truck duct. The bypass controller functions to control the operation of a bypass damper which regulates the airflow through a duct that bypasses air from the supply truck duct to the return. The bypass controller also measures the air flow via an air flow sensor and communicates with a microcomputer-controlled thermostat to coordinate transitions between heating and cooling cycles in association with a second sensor which monitors the duct temperature.

Abstract: A temperature control system used in association with a heating and cooling system supplying warm or cool air to a duct system for maintaining accurate temperature in a zone of multiple zones utilizing a microcomputer based thermostat for modulating a damper assembly in the duct system feeding the zone, thereby controlling the volume of air flow in the duct system to the zone to match the load in each zone. The thermostat has a digital readout display thereon indicating the temperature to be maintained in the zone and which can selectively display the duct temperature of air and/or the zone temperature of the air. The thermostat controls a damper assembly which includes a stepper motor for pivoting the damper blade between open and closed positions with the duct temperature sensor located before the damper blade in the duct. Calibration to provide setting of the zone temperature to conform with an accurate thermometer is provided in the thermostat, as well as selectable stop positions for the damper blade.

Abstract: A monitoring and control system for a heating, ventilating and air conditioning (HVAC) unit which provides zone control in plural zones in which each zone includes a control thermostat that is interfaced with the monitoring system so that each zone thermostat controls the HVAC unit as well as a damper unit for that particular zone thereby enabling independent zonal control in a multiple zone system which uses a single zone HVAC unit. The monitor considers individual zone needs, damper positions, amount of demand in the zone, mode of the zone damper and other factors which affect the comfort of zone occupants and, in response to signals from the thermostats, decides how and when to control the HVAC unit so that, in effect, a single zone HVAC unit becomes a multiple zone system.

Abstract: A bypass control system and method monitors and controls the amount of air recirculated through a bypass duct from the air supply outlet supplied by a fan and motor from a single zone HVAC unit to the air intake thereof, a stepper motor driven bypass damper is located in the bypass duct having a damper blade movable between opened and closed positions and intermediate positions therebetween, and a bypass monitor is connected to the bypass damper for controlling the operation of the stepper motor of the bypass damper.