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After the control of air flow and temperature was standardized, the use of electromechanical relays in ladder logic to switch dampers became standardized. Eventually, the relays became electronic switches, as transistors eventually could handle greater current loads. By 1985, pneumatic controls could no longer compete with this new technology ...
A thermal expansion valve is a key element to a heat pump; this is the cycle that makes air conditioning, or air cooling, possible.A basic refrigeration cycle consists of four major elements: a compressor, a condenser, a metering device and an evaporator.
A digital input indicates a device is on or off. Some examples of digital inputs would be a door contact switch, a current switch, an air flow switch, or a voltage-free relay contact (dry contact). Digital inputs could also be pulse inputs counting the pulses over a period of time.
Pneumatically actuated shut down valve A diagram of the internal components of a safety shutoff valve. When this type of valve is tripped, the flow is quickly stopped and an indicator disc tells the operator that the electrical circuit has been opened by a failure somewhere in the system.
Industrial pressure switches may have a calibrated scale and pointer to show the set point of the switch. A pressure switch will have a hysteresis, that is, a differential range around its setpoint, known as the switch's deadband, inside which small changes of pressure do not influence the state of the contacts. Some types allow adjustment of ...
On–off control uses a feedback controller that switches abruptly between two states. A simple bi-metallic domestic thermostat can be described as an on-off controller. When the temperature in the room (PV) goes below the user setting (SP), the heater is switched on. Another example is a pressure switch on an air compressor.
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Intumescent dampers swell shut due to intumescence in the event of a fire. Unlike mechanical dampers, it is a physical/chemical reaction that causes closure. Cleaning and an age assessment are periodically performed. The annulus of an intumescent damper is closed eliminating smoke migration.
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