Chapter 6

Outputs, Feedback, and Control

All technological systems are purposeful. They are designed to meet specific needs and wants of people. There is a direct relationship between the need and the output. These outputs can be categorized in three ways:

• Desirable - undesirable

• Intended - unintended

• Immediate - delayed

Desired

Goal Inputs Process Output Result

Indented/ Unintended

Desirable/ Undesirable

Immediate/ Delayed

Desirable & Undesirable Outputs

The needs for and outputs of technology are countless. Communication: information into media messages. Construction: products into structures. Manufacturing: materials into products. Transportation: energy through vehicle into relocating people and cargo. These are the desirable outputs of the system.

There are also undesirable outputs. For example, some manufacturing activities produce fumes and toxic chemicals by-products. If improperly treated these outputs poison the air and water around us. Construction project cause soil erosion. Communication can use billboards which some people find unsightly. Transportation systems create outputs we do not want. Exhaust fumes from cars and trucks pollute the air. All of these are examples of undesirable outputs.

Intended & Unintended Outputs Technological systems are designed to

produce specific outputs. These are the intended outputs. Depending on your point of view, the intended outputs may be desirable or undesirable. Technological systems produce outputs that were not considered when the system was designed. For example, some heating systems produced in the 40’s through the 60’s used asbestos to insulate pipes. People developed lung cancer. This was and unintended output of the system.

Immediate & Delayed OutputsMost technological systems are designed

to produce a product or service for immediate use. Some outputs have delayed effects. The chemical used as propellants in aerosol cans and as refrigerants are now affecting the ozone layer around the earth. This is an example of delayed, unintended, undesirable outputs of technology.

Feedback & Control

The people designing and using technology should strive to maximize the desirable results. The undesirable outputs can never be totally eliminated. They need to be held to a minimum.

Controlling systems is often viewed at the operating level. This view explores how processes are controlled so that outputs meet specifications. Political actions, personal value systems, international competition and other factors outside the system also exercise control.

Des

ired

G

oal

Inputs OutputProcess

Res

ult

Compare

Types of Control Systems

Two major types of control systems are used in technology. The simplest control system is the open-loop. This system uses no feedback to compare the results with the goal. The system is set and then operates without the benefit of output information. This is called open-loop control. Output information is not used to adjust the process in this type of control system.

Most technological systems use feedback in their control systems. This means that output information is used to adjust the processing actions. Feedback can be used to control various stages of factors within a system of the entire system. Systems using feedback are called closed-loop control system.

Marketing Research

Material Resource Control

Inventory Control

Inputs Process Outputs

Quality Control

Wage Control

Process Control

Cu

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S

atis

fact

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Cu

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N

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s &

Wan

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Components of Control SystemsTo ensure this happens we design control

systems with three major parts:

• Monitoring devices

• Data comparing devices

• Adjusting devices

Monitoring Devices

The first part of a control system gathers information about the action being controlled. It monitors inputs, processes, outputs, or reactions. The information gathered can be of many types. It can be very specific mathematical data, or more general opinions of customers. The type of information gathered during the monitoring step depends on how the data will be used.

Process operating information can be gathered using several types of sensors:

• Mechanical sensors

• Thermal sensors

• Optical sensors

• Electronic sensors

• Magnetic sensors

Comparing Devices

The information gathered by sensing devices is matched against expectations. The results are compared to the intent of the system. Analytical methods mathematically or scientifically make the comparison. Statistics may be used to see if the output meets the goal. The size of a part can be checked with lasers and compared with data in a computer file. This type of comparison is commonly used in closed-loop systems.

Judgmental systems use human opinions and values to enter into the control process. Open-loop control systems require human judgment.

Adjusting Devices

Comparing outputs to expectations may indicate that the system is not operating correctly. The system will need adjusting. This adjusting is done by controllers. They may speed up motors, close valves, increase the volume of burning gases, or a host of other actions.

System controllers can be several types:

• Mechanical Controllers

• Electromechanical Controllers

• Electrical and electronic controller

• Fluidic controllers

Operating Control Systems

Manual control systems require humans to adjust the processes.

Manual Control

A good example of a manual control system is the automobile

Automatic Control

Technological devices are used to monitor, compare, and adjust the system without human interference. A simple example of automatic control is thermostat in a heating system.

Monitor Compare Adjust

Feedback

Outside Influences as Control

Control also comes from outside the system. For example, establishing the 40 hour workweek was done through labor union influence and government action. Public opinion is also a control factor. The opinions of civic groups, churches, labor unions, and various associations affect public policies. The debate between environmentalists and forest products companies over timber cutting is one example

FEEDBACK

INPUTS PROCESS OUTPUT

EXTERNAL INFLUENCE AND CONTROL