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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 key switch (sometimes called a keyswitch or lock switch) is a key-operated switch. [1] Key switches are used in situations where access to the switch's functions needs to be restricted. [2] [3] Key switches are available as components with solder connections, and are available with a variety of ampere ratings. They may use tubular or other ...
Whenever the kiln power switch is turned on, the key is automatically held by the interlock, and cannot be manually removed. In order to open the kiln door, the power switch must first be turned off, which releases the key and allows it to be removed from the interlock. The key can then be used to unlock the kiln door.
For vacuum- or pneumatically operated zone valves, the thermostat usually switches the pressure or vacuum on or off, causing a spring-loaded rubber diaphragm or ball valve to move and actuate the valve. [2] Unlike the switch-monitored electrical zone valves, these valves automatically return to the default position without the application 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.
In control theory, a bang–bang controller (hysteresis, 2 step or on–off controller), is a feedback controller that switches abruptly between two states. These controllers may be realized in terms of any element that provides hysteresis. They are often used to control a plant that accepts a binary input, for example a furnace that is either ...
After receiving an operation command, the actuator moves the valve in direction OPEN or CLOSE. When reaching the end position, an automatic switch-off procedure is started. Two fundamentally different switch-off mechanisms can be used. The controls switch off the actuator as soon as the set tripping point has been reached. This is called limit ...
Valves and their types and identifications (e.g. isolation, shutoff, relief and safety valves, valve interlocks) Control inputs and outputs (sensors and final elements, interlocks) Miscellaneous - vents, drains, flanges, special fittings, sampling lines, reducers and swages; Interfaces for class changes; Computer control system