What does the PID do on my HI 3300 Tension Controller?

A tension control process is a dynamic system which is changing all the time. The actual tension changes from moment to moment. Most often, the actual tension will be greater or less than the set point. The HI 3300 Tension Controller produces a PID generated correction signal that is sent to the tensioning mechanisms (clutch, motor, brake, etc.) in order to maintain the tension set point. This correction signal is created by PID software in the controller. The control is used to limit the overshoot and slow the response in controlling the product.

The three main components of PID are explained below.

Proportional - More appropriately called "gain", which is a multiplier that increases the error signal to a value which is useful as a correction signal. The correction signal is proportional to the original error and either increases or decreases the tension to correct for the error signal from the load sensor.

Integral - More appropriately called "stability", which provides a correction to the PID algorithm that smoothes or slows the Controller output so that tensioning mechanisms do not overreact. This adds stability to the system.

Derivative - More appropriately called "response", which looks for the rate at which the error rate changes. The derivative accounts for and adjusts the output signal that corresponds to the rate of change. D is different from P in that D responds early to a rate of change and P only reacts to the absolute error signal at any given point in time.