Proportional Technology

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Proportional Controller Types

​A controller is a transfer element which compares the feedback value received from a transducer to a predetermined value and then outputs a control signal to the actuating element (proportional valve).  The output signale causes the valve opening to adjust until the set point is reached.

The controller will continue to adjust the output signal over time such that the dynamic qualities of the process to be controlled are well balanced.

The set point must be reached in as short a time as possible whilst the feedback value should fluctuate as little as possible around the set point.

Continuous-action controllers

The output of a continuous-action controller is a continuous signal (voltage or current) which adjusts the through all the intermediate values between the initial and a final value.

There are three types of controller. Proportional (P), Proportional and Integral (PI) and Proportional Integral and derivative (PID) each type of controller has applications that it is most suited to.  For a full explanation of the three types of control please visit this Wikipedia article

​​ P Controller PI Controller PID Controller

Application

P

PI

PID

PRESSURE

Low profile

Suitable

FLOW

/

Suitable

less suitable

TEMPERATURE

Low profile

Suitable

LEVEL

Suitable 

/

Suitable 

SPEED

Suitable


Switching controllers

As opposed to a continuous-action controller, this type of controller does not have a continuous output signal. The output signal can only be switched on or off. But this can also be used for controlling purposes.

Types of modulation:

  • Pulse width modulation (PWM): ASCO Numatics uses pulse width modulation in its electronic control units.

  • Pulse amplitude modulation 

  • Pulse frequency modulation

In pulse width modulation (PWM), the 24 V DC supply voltage is transformed into rectangular pulses with different width. The output signal is no longer a constant signal but a sequence of pulses which is repeated at a certain time interval, or period.​