Jaipur Engineering College and Research Centre

Year & Sem – 4th Year & VII Semester

Subject –Human Engineering and Safety (7AG6-60.1)
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Unit – 1 (Introduction: Objective, scope and outcome of the course)
Presented by –Ms. Anima Sharma, Assistant Professor

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Course Description & Objectives:

To impart the fundamental knowledge to the student on the importance of human engineering and safety in the
field of agriculture machinery

Course Outcome

At the completion of the course the student will be able to:

1. understand the importance of human factors and their application in system development and know the
effect of visual, auditory and factual displays in human performance.

2. Exposure to human factors for engineering design, measurement of energy cost of different activities.

3. be able to ideally design the work space in accordance to anthropometry

4. have the general understanding safety features and regulation acts in farm machinery.

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List of reference books:

1. Ernest and Mc Cormick, E.L. (1970). Human factors in engineering and design. Mc Graw Hill Co., New York.
2. Sanders M S., Human Factors In Engineering And Design 7th Edition, Tata Macgraw Hill

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 HUMAN FACTORS IN SYSTEM DEVELOPMENT -
CONCEPTS OF SYSTEM
1.1 Introduction
• Derived from two Greek words: “Ergon” meaning work “Nomos” meaning principles of laws
• Ergonomics is the science of work.
• DEFINITION: “The science of designing uses interaction with equipment and work place to fit the
job.” Ergonomics is also sometime called as:
• Man-Machine-Environment System, or
• Human Factors Engineering, or
• Human Engineering.
However; ERGONOMY it is not to be confused with AGRONOMY, which is related to Crop Sciences.

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 HUMAN FACTORS IN SYSTEM DEVELOPMENT -
CONCEPTS OF SYSTEM
1.1 Introduction
International Ergonomics Association Executive Council,
“Ergonomics (or human factors) is the scientific discipline concerned with the understanding of the interactions
among human and other elements of a system and the profession that applies theory, principles, data and methods
to design in order to optimize human well-being and overall system performance.”

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 HUMAN FACTORS IN SYSTEM DEVELOPMENT -
CONCEPTS OF SYSTEM
1.1 Introduction
• Ergonomics is the science of fitting the work environment to the employee.
• It improved employee comfort, reduce chances for occupation injuries, improved productivity and improved
job satisfaction.

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 HUMAN FACTORS IN SYSTEM DEVELOPMENT -
CONCEPTS OF SYSTEM
What are the Ergonomic Objectives?
• Improve the efficiency of operation
• To maximize productivity

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 HUMAN FACTORS IN SYSTEM DEVELOPMENT -
CONCEPTS OF SYSTEM
What are the Ergonomic scopes?
• Anthropometrics
• Physiology
• Psychology
• Biomechanics
• Anatomy
• Design

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 HUMAN FACTORS IN SYSTEM DEVELOPMENT -
CONCEPTS OF SYSTEM
Where to apply Ergonomics?
• Worker/Workplace (Accommodation)
• Physiological Stress (Prevention)
• Environmental Stress (Prevention)
• Tool and Equipment Design
• Error minimization in Material Handling

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 HUMAN FACTORS IN SYSTEM DEVELOPMENT -
CONCEPTS OF SYSTEM

What an Ergonomist do?

• Training Institutions (Universities and colleges)
• Service industry(consultancy, safety officer)
• Production Sector(Design Department, Research Department)

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 HUMAN FACTORS IN SYSTEM DEVELOPMENT -
CONCEPTS OF SYSTEM
Ergonomics or Man-Machine-Environment System deals with the machine or job, its operator and working
environment as a complete system affecting the intended work performance

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 HUMAN FACTORS IN SYSTEM DEVELOPMENT -
CONCEPTS OF SYSTEM
The working environment may involve workspace, controls, ambient environment, noise, dust, vibrations, smoke
and gases, light, safety concerns, etc. Ergonomics is an application of Medical and Engineering Sciences principles
related to human factors in the task concerned

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 THE OPERATOR-MACHINE-ENVIRONMENT SYSTEM
APPROACH
• The human has a limiting capability as a power of source in
comparison to the engine/ machine. However, it has a distinct advantage
in terms of its intelligence and decision making as per need.
• The operator acts as a core of the system. Operator uses his sensory
system to perceive the environment, takes decision based upon
information available, and finally takes appropriate action for desired
output.
• If the task is new and not well known to operator then the decision making
process is very slow.
• For routine and well known task, decisions are very quick and accurate.
• Stress is one of the variables that affect operator perception, decision
making, and response selection.
• Many factors including operator’s age, training, motivation, etc. affect the
success of task performance.
THE OPERATOR-MACHINE-ENVIRONMENT SYSTEM
APPROACH
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 THE OPERATOR-MACHINE-ENVIRONMENT SYSTEM
APPROACH
• The machine characteristics that are involved in the system are its
features, controls, displays, power availability, speed of operation,
seat, vibrations, noise, exhaust, visibility, safety features, etc.
• Workspace, controls layout and display arrangement affects the
operator capability to a large extent.
• For example, a tractor seat is designed for comfort of operator and easy
accessibility of controls like brake, steering, gears, clutch, etc.
• Noise, vibrations, dust, smoke, field conditions, are some of the other
major environmental factors that come into play, thereby affecting task
performance.
THE OPERATOR-MACHINE-ENVIRONMENT SYSTEM
APPROACH
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RELATIVE ADVANTAGES OF MAN AND MACHINE

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 BASIC PROCESS IN SYSTEM DEVELOPMENT

In Ergonomics, each of the human machine and

environment has an effect on the complete system. The
basic components of each are:

• Human Components
• Machine components
• Local environment

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 BASIC PROCESS IN SYSTEM DEVELOPMENT

Human Components:
• Sensors/ senses: Through which a human is made aware of its
surroundings. Human being has five senses namely right, hearing, touch,
taste and smell.
• Information processor: This includes joints, muscles and memory to
provide information and feedback and brain to act as information
processing system.
• Effectors: The three primary effectors are the hands, feet and voice.
However, the whole body more can be regarded as effecter because no
physical activity can be carried out without its supporting role.
BASIC PROCESS IN SYSTEM DEVELOPMENT
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 BASIC PROCESS IN SYSTEM DEVELOPMENT

Machine Components:
• Displays: These include gauges dials, meters, indicators, etc. and provide
information about status and working of machine to the operator.
• Controls: These include components of machine like steering wheel,
accelerator, clutch, brake lever etc. through which a human changes and
control action of machine.
• Controlled process: This is the basic operation of machine in its local
environment as controlled by the human.

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 BASIC PROCESS IN SYSTEM DEVELOPMENT

Local environment: It is the place and circumstances in which work carried

out. It consists of:
• Workspace: It is the three dimensional space in which work is being
carried out. It is decided by dimensions of the machine, anthropometry of
human and space required for activities of human and machine.
• Physical environment: It means the local environment factors having a
bearing on the complete system. It includes noise, vibrations, lights,
exhaust, climate etc.
• Work organization: It refers to the organizational structure in which work
activity is embedded. It includes role of human and machine in system,
organization and other persons of the team upon which the performance
depends.
BASIC PROCESS IN SYSTEM DEVELOPMENT
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 OBJECTIVE OF ERGONOMICS

While planning of the human factors in ergonomics, the objectives and end
goal required is to be taken into considerations. These objectives may be
one or a combination out of the following:
Basic objective:
• To improve system performance
• To reduce errors
• To increase safety

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 OBJECTIVE OF ERGONOMICS

Objectives concerning users and operators:

• To increase ease of use
• To reduce fatigue and physical stress
• To improve the working environment
• To increase user acceptance
• To improve aesthetic appearance.
Objectives concerning reliability and logistic support:
• To improve reliability
• To reduce maintenance
• To reduce labour requirement
• To reduce training requirement
Other objectives:
• To improve system efficiency
• To reduce cost of production

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 HUMAN TECHNOLOGY INTERACTION

Ergonomics and technology have a specific role to play with each other.
The technology can be defined as entire system of people and organizations, knowledge,
process and devices that go into creating and operating technological artifacts. Technology is a
product and process involving both science and engineering.
Engineering represents ‘design under constraints’ of cost, reliability, safety, environmental
impact, ease of use, available human and material resources, manufacturability, government
regulations, laws and politics.
Ergonomics discovers and applies information about human behavior, abilities, limitations and
other characters to the design of tools, machines, systems, tasks jobs and environments for
productive, sofa, comfortable and effective human use.
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 HUMAN TECHNOLOGY INTERACTION

The basic issues and processes covered under Ergonomics for design and development are:
A. Human Characteristics
1. Psychological aspects
2. Physiological and anatomical aspects
3. Group factors
4. Individual differences
5. Psycho physiological state variables
6. Task-related factors

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 HUMAN TECHNOLOGY INTERACTION
B. Information Presentation and Communication
1. Visual communication
2. Auditory and other communication
modalities 3.Choice of communication media
4.Person–machine dialogue mode
5. System feedback
6. Error prevention and recovery
7.Design of documents and procedures
8.User control features
9. Language design
10. Database organization and data retrieval
11.Programming, debugging, editing, and programming
aids 12.Software performance and evaluation
13.Software design, maintenance, and reliability

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 HUMAN TECHNOLOGY INTERACTION
C. Display and Control
E. Environment
Design 1.Input devices and
1.Illumination
controls 2.Visual displays
2.Noise
3.Auditory displays
3.Vibration
4.Other modality displays 4. Whole body movement
5.Display and control characteristics
5. Climate
D. Workplace and Equipment Design
6. Altitude, depth, and space
1.General workplace design and
7.Other environmental issues
buildings 2.Workstation design
F. System Characteristics
3. Equipment design
1.General system features

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 HUMAN TECHNOLOGY INTERACTION

G. Work Design and Organization 9. Use of support

1.Total system design and 10. Technological and ergonomic change
evaluation 2.Hours of work H. Health and Safety
3.Job attitudes and job satisfaction 1.General health and safety
4.Job design 2.Etiology
5.Payment systems 3. Injuries and illnesses
6.Selection and screening 4. Prevention
7.Training
8. Supervision

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 HUMAN TECHNOLOGY INTERACTION

I. Social and Economic Impact of the System 11. Political comment and ethical considerations
1. Trade unions J. Methods and
2. Employment, job security, and job Techniques 1.Approaches
sharing 3.Productivity and methods 2.Techniques
4.Women and work 3.Measures
5.Organizational
design 6.Education
7.Law
8.Privacy
9. Family and home life
10. Quality of working life

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 FACTORS CONSIDERED IN SYSTEM DEVELOPMENT
Some of the important factors considered in design, testing and evaluation of man-machine-environment system are as
listed by Dul and Weerdmeester (1993).
A. Anthropometric, biomechanical, and physiological factors:
1.Are the differences in human body size accounted for by the design?
2.Have the right anthropometric tables been used for specific populations?
3.Are the body joints close to neutral positions?
4. Is the manual work performed close to the body?
5. Are any forward-bending or twisted trunk postures involved?
6.Are sudden movements and force exertion present?
7. Is there a variation in worker postures and movements?
8. Is the duration of any continuous muscular effort limited?
9. Are the breaks of sufficient length and spread over the duration of the
task? 10.Is the energy consumption for each manual task limited?

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 FACTORS CONSIDERED IN SYSTEM DEVELOPMENT
B. Factors related to posture (sitting and standing):
1. Is sitting/standing alternated with standing/sitting and walking?
2. Is the work height dependent on the task?
3. Is the height of the worktable adjustable?
4. Are the height of the seat and backrest of the chair
adjustable? 5.Is the number of chair adjustment possibilities
limited?
6.Have good seating instructions been provided?
7.Is a footrest used where the work height is fixed?
8.Has work above the shoulder or with hands behind the body been avoided?
9.Are excessive reaches avoided?
10. Is there enough room for the legs and feet?
11. Is there a sloping work surface for reading tasks?
12. Have combined sit–stand workplaces been introduced?
13. Are handles of tools bent to allow for working with the straight wrists?
FACTORS CONSIDERED IN SYSTEM DEVELOPMENT
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 FACTORS CONSIDERED IN SYSTEM DEVELOPMENT
C. Factors related to manual materials handling (lifting, carrying, pushing and pulling loads)
1. Have tasks involving manual displacement of loads been limited?
2. Have optimum lifting conditions been achieved?
3. Is anybody required to lift more than 23 kg?
4. Have lifting tasks been assessed using the NIOSH
method? 5.Are handgrips fitted to the loads to be lifted?
6. Is more than one person involved in lifting or carrying tasks?
7. Are there mechanical aids for lifting or carrying available and used?
8. Is the weight of the load carried limited according to recognized guidelines?
9.Is the load held as close to the body as possible?
10. Are pulling and pushing forces limited?
11. Are trolleys fitted with appropriate handles and handgrips?

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 FACTORS CONSIDERED IN SYSTEM DEVELOPMENT
D. Factors related to the design of tasks and jobs
1. Does the job consist of more than one task?
2. Has a decision been made about allocating tasks between people and
machines? 3.Do workers performing the tasks contribute to problem solving?
4. Are difficult and easy tasks performed interchangeably?
5. Can workers decide independently on how the tasks are carried out?
6.Are there sufficient possibilities for communication between
workers? 7.Is sufficient information provided to control the tasks
assigned?
8. Can the group take part in management decisions?
9. Are shift workers given enough opportunities to recover?
FACTORS CONSIDERED IN SYSTEM DEVELOPMENT
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 FACTORS CONSIDERED IN SYSTEM DEVELOPMENT
E. Factors Related to Information and Control Tasks
(i) Information
1.Has an appropriate method of displaying information been selected?
2.Is the information presentation as simple as possible?
3.Has the potential confusion between characters been avoided?
4.Has the correct character/letter size been chosen?
5.Have texts with capital letters only been avoided?
6.Have familiar typefaces been chosen?
7.Is the text/background contrast good?
8.Are the diagrams easy to understand?
9.Have the pictograms been used properly?
10.Are sound signals reserved for warning purposes?

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 FACTORS CONSIDERED IN SYSTEM DEVELOPMENT
E. Factors Related to Information and Control Tasks
(ii) Control
1. Is the sense of touch used for feedback from controls?
2.Are differences between controls distinguishable by touch?
3.Is the location of controls consistent, and is sufficient spacing provided?
4.Have the requirements for control–display compatibility been considered?
5. Is the type of cursor control suitable for the intended task?
6.Is the direction of control movements consistent with human
expectations? 7.Are the controls objectives clear from the position of the
controls?
8. Are controls within easy reach of female workers?
9. Are labels or symbols identifying controls used properly?
10.Is the use of color in controls design limited?
FACTORS CONSIDERED IN SYSTEM DEVELOPMENT
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 FACTORS CONSIDERED IN SYSTEM DEVELOPMENT
E. Factors Related to Information and Control Tasks
(iii) Human–computer interaction
1. Is the human–computer dialogue suitable for the intended task?
2. Is the dialogue self-descriptive and easy to control by the user?
3.Does the dialogue conform to the expectations on the part of the
user? 4.Is the dialogue error-tolerant and suitable for user learning?
5. Has command language been restricted to experienced users?
6. Have detailed menus been used for users with little knowledge and
experience? 7.Is the type of help menu fitted to the level of the user’s ability?
8.Has the QWERTY layout been selected for the keyboard?
9.Has a logical layout been chosen for the numerical keypad?
10.Is the number of function keys limited?
11.Have the limitations of speech in human–computer dialogue been considered?
12.Are touch screens used to facilitate operation by inexperienced users?

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 FACTORS CONSIDERED IN SYSTEM DEVELOPMENT
F. Environmental Factors
(i) Noise and vibration
1. Is the noise level at work below 85 dBA?
2. Is there an adequate separation between workers and source of noise?
3.Is the ceiling used for noise absorption?
4. Are acoustic screens used?
5. Are hearing conservation measures fitted to the
user? 6.Is personal monitoring to noise/vibration used?
7.Are the sources of uncomfortable and damaging body vibration recognized?
8.Is the vibration problem being solved at the source?
9. Are machines regularly maintained?
10. Is the transmission of vibration prevented?

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 FACTORS CONSIDERED IN SYSTEM DEVELOPMENT
F. Environmental Factors
(ii) Illumination
1. Is the light intensity for normal activities in the range 200 to 800 lux?
2. Are large brightness differences in the visual field avoided?
3. Are the brightness differences between task area, close surroundings, and wider surroundings
limited? 4.Is the information easily legible?
5.Is ambient lighting combined with localized lighting?
(iii) Climate
1. Are workers able to control the climate themselves?
2. Is the air temperature suited to the physical demands of the
task? 3.Is the air prevented from becoming either too dry to too
humid? 4.Are drafts prevented?
5.Are the materials/surfaces that have to be touched neither too cold nor too hot?
6.Are the physical demands of the task adjusted to the external climate?
7.Are undesirable hot and cold radiation prevented?
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 HUMAN PERFORMANCE
• The ergonomic aspects during application in agricultural machinery are of great importance as the
operator has to operate the machine in field.
• The physiological as well as psychological fatigue affects performance of the operator and hence,
man-machine-
environment system.
• There are many factors acting as stress on the operator during the work. These stresses may be due to
workload, immobilization for longer duration work, ambient temperature, relative humidity, vibrations,
noise, dust, smoke, exhaust gases, etc.
• A feeling of chance of accident during work, space confinement, overload of information to be handled,
etc. results in psychological fatigue.
• During the ergonomic studies, these stresses can be measured in terms of strain on the operator.
• The most important among physiological strains are related to heart activity, respiration, discomfort,
muscular fatigue,
etc.
• During ergonomical studies, stress on eyes, hearing loss, errors, speed of work, work performance
are some of the commonly used parameters for measurement of
 HUMAN PERFORMANCE
psychological/ mental strain.

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HUMAN PERFORMANCE

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HUMAN PERFORMANCE

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 PHYSIOLOGICAL FACTORS FOR MEASUREMENTS
Physical activities stimulate certain physiological responses in human beings. These
responses provide basis for human energy expenditure and fatigue. The physiological
measurements are made generally in terms of heart and respiration activities.
1. Heart rate
• Heart rate (HR) is the most reliable dependent parameter in ergonomic studies.
• This is because the heart rate has a direct and linear relationship with the human
workload and stress.
• A starting period of 2-3 minutes is sufficient for heart/pulse rate to stabilize depending
upon nature of exercise. Also, care has to be taken so that the operator is not subjected
to workload leading to heart rate more than HRmax i.e. the upper limit of heart rate

allowed during an activity. Here,

HRmax (beats/min) = 220 – Age (years)------------------------------------(1)
PHYSIOLOGICAL FACTORS FOR MEASUREMENTS
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 PHYSIOLOGICAL FACTORS FOR MEASUREMENTS
2. Respiration rate
• It is measured in terms of rate of volume of air inhaled or air exhaled or oxygen intake (VO2) or respiration
rate.
• The greater the demands made on the muscle by the physical activities, the more air or oxygen is inhaled.
• The human energy expenditure (kilo Joule, kJ) is computed by multiplying the oxygen consumption (litres,
l) with the calorific value of oxygen (20.88 kJ/l).
• The human workload has been categorized between light work and extremely heavy work depending upon
heart rate or oxygen consumption.
• Another criterion for measurement of human performance is Relative Load (RL) which is expressed as
percentage of maximum aerobic power (VO2max); where, VO2max is volume of oxygen intake corresponding
to HRmax calculated from established relation between VO2 and HR of an individual through subject
calibration on treadmill or bicycle ergometer.
• Daily (8 hours) physical activity involving 35% of VO 2max might be considered as an acceptable workload
(AWL) for Indian workers.
PHYSIOLOGICAL FACTORS FOR MEASUREMENTS
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PHYSIOLOGICAL FACTORS FOR MEASUREMENTS

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 PHYSIOLOGICAL FACTORS FOR MEASUREMENTS
3. Discomfort rating
Body posture is one of the major factor which causes muscular fatigue and discomfort in the body.
Uncomfortable body posture in different activities reduces work efficiency, capacity and safety of operator.
The effect due to working posture can be measured in terms of overall discomfort rate and body part
discomfort rate techniques.
PHYSIOLOGICAL FACTORS FOR MEASUREMENTS
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 PERFORMANCE RELIABILITY
Performance reliability refers to quantitative values that characterize the
dependability of system or components performance. The reliability of system
can be defined in many ways:
 Reliability is probability of a system performing its intended function over a
given period
of time under the operating condition encountered.
 Reliability is the probability that a system will operate without failure for
a given period of time under given operating conditions.
 Reliability is mean operating time between two successive failures.
 Reliability is integral of distribution of probabilities of failure free operation.
PERFORMANCE RELIABILITY
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 PERFORMANCE RELIABILITY
Components in series
System consists of number of components connected in series i.e. system
operates if all are OK and system fails if any one of components fails. So
weakest link i.e. component having lowest possibility of survival is the most
critical one

Here, reliability of system (Rs) is product of reliability of each and every

individual component connected in series.
Thus; Rs = R1 x R2 x R3 x……… Rn
PERFORMANCE RELIABILITY
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 PERFORMANCE RELIABILITY
Components in parallel
Parallel system involves more cost, but is more reliable because if any of the components in parallel is
functioning, that means system is in working order. The system fails only if each and every component connected
in parallel fails simultaneously. Reliability of system (Rs) is determined after calculating probability of failure of

the system
(Qs)

Thus; Rs = 1 – Qs------------------------------------------------------------------------------------------------------------- (3)

Where, Qs = Q1 x Q2 x Q3 x……… Qn----------------------------------------------------------------------------(4)
Here, Qi is failure probability of ith component.
PERFORMANCE RELIABILITY
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 INFORMATION INPUT PROCESS
• “Information” is the transfer of energy that has meaningful implications in any given situation;
e.g. a driver communicating with his tractor through displays and controls.
• The input to the operator is the information received through the sense organs.
• Our sensory mechanisms are sensitive to certain stimuli, which convey meaning to us.
• The stimuli are various forms of energy, such as light, sound, heat, and mechanical pressure.
• Information from the original source may be direct (e.g. a visual signal of undulated field), or
indirect (e.g. quantity of fuel in tractor tank through fuel meter on display board, change in
sound of tractor engine).
• The humans are continually bombarded with stimuli from our immediate environment, these
stimuli consisting of various forms of energy to which our senses organs are sensitive.

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 INFORMATION INPUT PROCESS

It is noticed that usually multiple senses operate at the same time. For example, driver of a tractor uses
eyes, ears and skin or all of them at same time.

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 INFORMATION PROCESSING SYSTEM
• How humans perceive and process information must be taken into account in order to design interfaces that
can be learned and used efficiently.
• In all human-system interactions, the user must perceive information, process information, and make
decisions based on that information, leading to responses and actions.
• For example, the human eye receives visual information and codes information into electric-neural activity
which is fed back to the brain where it is stored and decoded. This information can be used by other parts of
the brain relating to mental activities such as memory, perception and attention.

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 INFORMATION PROCESSING SYSTEM
Information processing system consists of a series of stages, which represent stages of
processing. Arrows
indicate the flow of information from one stage to the next.

Input processes are concerned with the analysis of the

stimuli. Storage processes cover
everything that happens to
stimuli internally in the brain and can include
coding and manipulation of the stimuli. Information
stored can be a short term or a long term memory.
Output processes are responsible for preparing an appropriate
response to a stimulus.
INFORMATION PROCESSING SYSTEM
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 MEASUREMENT OF INFORMATION
• Information is measured in bits (binary unit). A bit is defined as the amount of information obtained from
one of two equally likely alternatives specified. When various alternatives are equally probable, the
amount of information is given by formula:
(1)

Where, H is amount of information in bits, and n is number of equally probable alternatives.

• If n is 2 then H is logarithm of 2 to the base 2, which is 1.
• For example, if there are four lights on a panel and only one of them may be on at a time, then we have
two bits of information. Equation 1 can be written in terms of probability of each alternative, where
probability is the reciprocal of n. Therefore;
(2)

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 STIMULUS CHARACTERISTICS
• The stimulus inputs that human receive via any sensory modality (vision, audition etc.) differ in
terms of their characteristics.
• For example, visual characteristics include shape, configuration, size, position, color, etc.
• The auditory characteristics include sound pressure level, frequency, duration,
continuous/intermittent signal, etc.

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 DISPLAYS FOR INFORMATION INPUT
• Displays can be either dynamic or static.
• Dynamic displays are continually changing or are subject to change with time, e.g.
temperature or pressure gauge, fuel gauge, ampere meter, RPM meter, speedometer,
monitors and displays, TV and radio signal, etc.
• Static displays remain fixed over time, e.g. signs, charts, graphs, labels etc.
• There is a need of presenting information to people by use of displays in such a
manner so that usefulness of information under given conditions is enhanced
affectively.
DISPLAYS FOR INFORMATION INPUT
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 INFORMATION PRESENTED BY DISPLAYS
Major types of information presented by displays are described below.
1. Quantitative information: Such displays present quantitative value of some variable like temperature, pressure, speed, etc.
2. Qualitative information: Such displays provide approximate value, trend, rate or direction of change. E.g. ampere meter of chargeable
battery, RPM meter showing approximate value, etc.
3. Status information: Such displays present condition or status of a system. E.g. ON-OFF indicators, stop-caution-go lights, indicator for
reverse gear, warning indicators, battery status indicator, etc.
4. Warning and signal information: Such displays indicate emergency or unsafe conditions or absence of some object/ conditions. E.g. aircraft
or lighthouse bacons, reverse light indicators, turning indicators, brake light indicators, signal for low/high beam light, seat belt signal, door
open signal, fuel refill indicator, etc.
5. Representational information: Such displays provide pictorial or graphic representation of objects areas or other configurations. E.g. movies,
photographs, maps, charts, diagrams, graphs, door open signal, seat belt indicator, heart beat shown on heart rate monitor, etc.
6. Identification information: Such displays are used to identify a particular condition, situation or object. E.g. sign boards on the roads, traffic

lights, color coded signals, etc.

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SELECTION OF SENSORY MODALITY

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 MAJOR TYPES AND USES OF DISPLAYS
Classification of displays
Displays provide useful and required information in a conveniently presentable form.
Displays can be broadly classified under three categories:
• Visual displays
• Auditory displays
• Tactual displays

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 MAJOR TYPES AND USES OF DISPLAYS
Visual displays
They are the most common in use and involve visual
capabilities and skills of users. The commonly used types
of visual displays are discussed here.
1. Quantitative visual displays
These displays provide information about quantitative
value and some variable, which may be a dynamic variable
such as temperature or speed, or a static variable such as
measurement of length with a ruler. Such displays have
units written along with quantity of variable. There are
three basic types of dynamic quantitative visual displays
1. Fixed scales with moving pointers
2. Moving scales with fixed pointers
3. Digital displays or counters
Fixed scale with moving pointer type displays are mostly
preferred; however, for long scales displays having
circular or tape type moving scales are preferred. Digital
displays used if values remain long enough to read.
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 MAJOR TYPES AND USES OF DISPLAYS
2. Qualitative visual displays
Such displays provide approximate value, trend, rate or direction of change. Quantitative data is used as a basis
for qualitative reading in at least three different ways:
• To convey information about status or condition of variable falling within limited number of predetermined
ranges. E.g. temperature gauge to determine if engine whether engine is cold/ normal/hot.
• To maintain roughly a desirable range of values. E.g. speedometer showing range of speed between 0-50
mph for safer control.
• To observe trends, rate of change, etc. E.g. engine RPM meter.

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 MAJOR TYPES AND USES OF DISPLAYS
3. Status indicators
They provide approximate information as an indication of status of a system or component. E.g. temperatures
gauge to dip it if the engine is cold/normal/hot. Other examples include ON/OFF indicator, traffic light on roads
etc (Fig.5.3). If a quantitative instrument is to be used only for check-reading purpose, status indicator should
be preferred.
4. Signal and warning lights
Flashing and steady state lights are used for various purposes viz. indications of lower/upper beams of lights,
warning lights for low-battery, low-fuel, seat-belt not used, door-open, engine-oil level low, low brake-oil,
hand-brake ON, reverse gear engaged, beacons, etc (Fig.5.4). Detection of signals and warning lights may
depend upon size, luminance, color, background, exposure time, and flash rate.
5. Representational display
Representational displays may be pictorial i.e. intended to reproduce an object/scene or may be
symbolic/illustrative. The purpose of such display is to convey a visual impression that requires little
interpretation. For example: aircraft position display, GPS for road map, charts and graphs, etc (Fig. 5.5).

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 MAJOR TYPES AND USES OF DISPLAYS
6. Alphanumeric and related displays
The effectiveness of such displays depends upon various factors like typography, content,
selection of words, color, background, contrast, illumination, and writing styles. The
typography of alphanumeric information includes stroke width, aspect ratio, font type, font size,
spacing of characters, spacing between lines, margins, color, etc. The communication of
message by such displays depends upon visibility, legibility, and readability (Fig. 5.6).
7. Visual codes symbol and signs
In our daily life we use a variety of visual codes symbols and signs which convey their intended
meaning. They includes numerals, letters, geometrical shapes, colors, configurations, symbolic
shapes representing various objects and messages.

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 AUDITORY DISPLAY
• The auditory displays involve sound as a signal.
• In a human-machine interface, the frequency and intensity/amplitude are two primary
attributes of sound.
• In general, the human ear is sensitive to sound waves having frequency range between
20- 20,000 Hertz (Hz).
• Intensity of sound or sound pressure level is generally measured in decibel (dB).
• A decibel is one-tenth of a bel (named after Alexander Graham Bell) and is expressed as a
ratio on logarithmic scale. The Sound pressure level (SPL), measured in decibels, can be
written as:
SPL = 20 log Po/Pr------------------------------------------------------------------------------------------- (1)
Where, Po is root mean square (rms) acoustic pressure at point of consideration, and Pr is
reference pressure (20 µPa).
AUDITORY DISPLAY
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 AUDITORY DISPLAY
• Circumstances under which auditory displays are preferred:
a) When the origin of a signal itself is a sound.
b) When the message is simple and short.
c) When the message doesn’t need to be referred afterwards.
d) When the message deals with events in time.
e) When the message calls for immediate action.
f) When the visual display system is overloaded.
g) When illumination limits use of vision.
h) When the operator moves away from visual display.
• The commonly used auditory displays are radio signals (dot-dash system) or warning and
alarm signals. The commonly used devices for warning and alarm signals are horn, whistle,
siren, bell, buzzer, chimes, etc.

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 TACTUAL DISPLAY
• Tactual displays use cutaneous (skin or somesthetic) senses.
• Such displays utilize a qualitative or comparative sensation of thermal or
mechanical or chemical or electrical stimulus.
• Thus its use is only to a very limited extent or under special conditions.
• Braille is particularly important for people who are visually impaired.
• The Braille display and textual maps are good examples of tactual displays.
• Another use of tactual senses control knobs.
• The coding of such devices for tactual identification includes their shape, texture
and size.
• Vibrator of a cell phone that uses a mechanical stimulus is another example of our
daily life.

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NAME OF FACULTY (POST, DEPTT.) , JECRC, JAIPUR 8