Question

Q12.

Self-Tuning controllers must first be programmed with initial PID values, to form boundary parameters. Once this has been done, they are capable of tuning a process more precisely. TRUE or FALSE?

Q13.

With a sketch please explain the concept of hysteresis, when dealing with some of the older instruments.                                                                                                                                   

Answer 1

Q. 12) TRUE

Q. 13) Hysteresis: - It is defined as the magnitude of error caused in the output for a given value of input, when this value is approached from opposite direction i.e. from ascending order ansd then descending order. This is caused by backlash , elastic deformation but is mainly caused due to frictional effects.
Hysteresis effects are best eliminated by taking observation in both the direction i.e. in ascending and then descending order values of input and then taking the arithmetic mean.

The two types of the hysteresis loops are shown in the figure below:

Dead time is defined as the time required by a measurement system to begin to respond to a change in measurand.

Dead Zone is defined as the largest change of input quantity for which is no output of the instrument.