Assignment 1 Solutions Flashcards

Flashcards for Assignment 1 Solutions

Four Elements of an Automatic Process Control System

Process, Measurement, Controller, Final Control Element

Open Loop vs. Closed Loop System

Open loop systems have no feedback and are manually operated. Closed loop systems use feedback to automatically adjust the final control element.

Examples of Disturbances Affecting a Control System

Changes in ambient conditions, demand for product, or supply of feed materials.

Error vs. Offset Error

Error is the difference between the measurement (PV) and the set point (SP). Offset error is a steady-state error that remains after corrective action.

Standard Analog and Pneumatic Signal Ranges

Analog: 4-20mA (or 1-5Vdc). Pneumatic: 3-15 PSI

Examples of Analog Input and Output Devices

Analog Input: Transmitter (pressure, temperature, flow). Analog Output: Valve, VFD speed, damper position.

Time Constant vs. Dead Time vs. Transfer Lag

Time Constant: Time to reach 63.2% of total change. Dead Time: Time before a change is observed. Transfer Lag: Time for the process variable to reach its final value.

Underdamped vs. Overdamped vs. Critically Damped; Quarter Amplitude Decay

Underdamped: Cyclic response with oscillations. Overdamped: No oscillations, slow return. Critically Damped: Quickest return with no oscillations. Quarter Amplitude Decay: Amplitude decreases by ¼ every half cycle.

Physical Construction Characteristics for Transmitter Selection

Electronic vs. pneumatic, Signal range and impedance, Analog bandwidth and sample rate, Measurement resolution, Output number and communication protocol, Temperature range, Process connections, Electrical connections, Process wetted parts material

Acronyms: ILD, P&ID, PFD

ILD: Instrument Loop Diagram (wiring). P&ID: Piping and Instrumentation Diagram (piping, mechanical equipment, instruments). PFD: Process Flow Diagram (general interrelationship between process equipment).

What do TT, TIC, TY, TV stand for?

TT – Temperature Transmitter; TIC – Temperature Indicating Controller; TY - Temperature Relay (IP Converter); TV – Temperature Valve

What is the purpose of the I/P symbol?

To show the conversion from an electrical to a pneumatic signal through the use of an I/P converter

What do the four line types mean (solid, dashed, double // and X)

Solid line – Process connection; dashed line – Electrical signal; double // - Pneumatic signal; X – Capillary Tube

All of the devices have the same number. Why not give them all unique numbers?

To show the relationship between each component in the same control loop