Controllers

In the second and third implementation floating control is achieved. For this two detectors are required for different settings. In the second implementation, the output of the controller is served on the engine that drives the camshaft. If the signal detectors above them both, the motor is driven in one direction. If it is below them as it is driven in the other direction. If there is no motor. Cams shaft cause on-off signals of controlled devices, for example. number of pumps in parallel. Thus, the signal in one direction causes the number of pumps to increase and signal in the other direction causes the works on the decline. The speed with which the changes depends on the gear motor.

In the third implementation, operation is identical, but this is all done electronically in the controller. Thus, the controller has two inputs and, as many results as a controlled devices. Some detectors combined in one instrument suitable Converter that can perform some functions of the controller. For example, for pneumatic systems of primary includes a sensing element variable air jet, thus modulation of air pressure, which is transmitted for further controller or directly to the managed device. Electrical and electronic detectors, such as infrared detector include sensing and amplifying the scheme of the device.

Controllers, as a rule, for use with proportional detectors measure the shift of the signal from a given point, and transmit the signal to the control device(s) signals, based on the PID algorithm. Any one or two, three PID conditions can be zero. In refrigeration, it is normal for the D-term equal to zero, so that the control is PI - proportional and integral. The controller can be arranged to receive input signals from more than one detector, for example. the temperature of hot water heating system may be lifted at the request of outdoor detector if the temperature drops, or may start the heating earlier in the morning heat the building before it is occupied; servo ago regulating valve (Fig. 9.7) can answer as evaporator pressure and temperature loads. With the advent of the microcomputer devices virtually any combination of signals can be processed using electronic controller, providing the output signals can be made consistent, and do not contradict each other.

Pneumatic controllers, which may include part of a sensing device, supplied with compressed air in 1bar sensor, which allowed to escape from the hole is controlled by the sensor. The resulting pressure modulates about 0.4 bar and is used in servo piston, diaphragm or bellows for the motion of a managed device (see Fig. 28.3).

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