Deck 17: Process Control Signals, Scaling, and Pid Instructions

Question 1

An analog signal that is used to control a device that has a direct influence on the process being controlled is called the control variable (CV), or ____________________.

Answer 1

final control element

Question 2

This information can include such things as temperature, pressure, level, flow, weight, etc., and is commonly referred to as the ____________________.

Answer 2

process variable (PV),process variable,PV

Question 3

Explain a process controller.

Answer 3

The process controller can be a stand-alone device or a software instruction that is part of a larger control system. A process controller has analog inputs and outputs that are used to monitor and control the process. In addition to the process connections, the process controller will also have a means to enter the desired setpoint, as well as the ability to make adjustments to various parameters that are designed to tune the process controller for a given process. Some process controllers that are used for temperature control may have the analog output converted to a time proportioning on/off output for driving a heater or cooling unit.

Question 4

The SCP instruction is a true logarithmic scaling instruction and does not share the same limitations as that of the Scale (SCL) instruction.

Question 5

The major limitation of the Scale (SCL) instruction is that all parameters must be ___________________.

Question 6

The same analog signal conversions described for process variable signals also apply to control variable signals.

Question 7

In 1942, J.G. Ziegler and N.B. Nichols published two loop tuning techniques that are still used today by many control engineers and technicians, which are called the ultimate gain method and the ____________________ method.

Question 8

A standard analog signal has a value that uniquely corresponds to the process variable being measured.

Question 9

Explain the six parameters of the SCP instruction.

Question 10

To maintain measurement accuracy of process variable signals, every signal conversion required must be done correctly and accurately.

Question 11

Explain how process variables turn into displayable or usable information for a PLC.

Question 12

Explain how to calculate the scaled value for a given input value if both the minima and maxima are known.

Question 13

Explain the parameters of the Scale (SCL) instruction.

Question 14

The Scale (SCL) instruction has limited applications when performing scaling operations.

Question 15

The control variable is also referred to as a(n) ____________________, and more correctly so if it does not have a direct influence on the process being controlled, as is the case with an analog display.