Johnson Controls Gmbh

Scott B Bramow

Richard N Laakaniemi

Paul E Wichman

Thomas M Holloway

William J Riebe

Louis J Crum

A square root signal extractor generates an output signal which is a square root function of an input signal. First and second diaphragm amplifiers have cascaded output chambers connected to a high gain output amplifier. The first and second amplifiers are connected as the non-inverting input and the inverting input respectively of the operational amplifier. A high gain output diaphragm amplifier is connected to the inverting amplifier output. The output diaphragm amplifier is constructed such that only a low level input pressure change is required to create a full swing of the output pressure. A non-linear input restrictor and a linear feedback resistor are connected to the input chamber of the inverting amplifiers. The feedback resistor has a significantly greater resistance than the input resistor. The non-inverting diaphragm amplifier is connected to the transmitter by a fluid repeater. A reference signal source is connected to the input restrictor and thus to the inverting input. The input restrictor is selected such that the differential pressure across the restricter is the square root of the flow. An adjustable fluid resistor is connected between the non-inverting and the inverting inputs which creates a flow path between the transmitter and reference source. The fluid repeater prevents loading of the transmitter.

Fluid signal square root extractor

A dual thermostat apparatus includes two thermostats which generate fluid control signals proportional to room air temperature. The thermostats are matched leakport pressure sensors having a signal orifice and a bimetal lid element to generate back pressure signals linearly related to temperature. The bimetal elements have adjustment cams to set the reference position with respect to the orifice. The cams are connected to a common shaft and dial to provide simultaneous and opposite readjustment with respect to the reference pressures. The signals are applied to separate signal chambers of the duplex relay, with a pressure regulator connected to the heat signal chamber to limit the operative pressure level of the heating signal to a selected maximum switchover pressure. The duplex relay controls a pressure supply valve for supplying a proportional pressure signal to a common output line to pneumatic operators of a heating valve and a cooling valve. The regulator and duplex relay create a control in which the heat pressure signal operates to one side of said reference pressure and the cooling signal controls to the opposite side of such reference pressure. The position of the cams sets the required temperature related movement before the operative back pressure signal is established and thus defines a dead band region in which neither heating or cooling is provided. The signal switchover becomes operative only in accordance with the dead band setting and thus a range in which neither the heating valve or cooling is actuated to conserve energy.

Dual thermostat control apparatus with dead band response

A mixed air conditioning controller is formed as a factory assembled and adjusted unit in a compact housing, with simple and direct input/output field connectors. Various temperature and humidity input devices are field connected to produce a sequenced control of the air dampers and mechanical cooling and heating devices, as well as auxiliary devices. The controller includes a primary input related to room demand, an outside air temperature input, with an interlocked control to the damper, a fan status input, a minimum air supply control and a by-pass switch having a low limit input. The logic network connecting the input/output includes pneumatic switching, pressure selecting and comparing devices of a diaphragm-controlled-orifice construction connected to function as fluidic repeaters, pressure regulating valves and pressure isolating and switching devices. The controller includes a conditioning channel and a damper channel. An outside air interlock controls the damper channel and a presettable switch controls the minimum air supply control. The presettable switch also includes a low limit temperature signal input. An auxiliary output may drive a humidity controller having a conditioning channel and a humidity channel. The humidity controller includes an interlock network connected to transfer the humidity input signal to the conditioning channel and a switch means controlled by the auxiliary output of the temperature controller.

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Oak Creek, WI, United States of America

Scott B Bramow