• Ergonomics is defined as the scientific study of the man-machine-working environment relationship and the application of anatomical, physiological and psychological principles to solve the problems arising from the relationship.
• Ergonomics is related to the comfort between the man and machine while operating the machine.
• The objective of ergonomics is to make the machine fit for user rather than to make the user adapt himself or herself to the machine.
• From design consideration, the topics of ergonomics studies are as follows:

1. Anatomical factors in the design of driver's seat:

The design of driver's seat of an automobile is such that it is adjustable and comfortable to the end user.

2. Layout of instrument dials and display panels for accurate perception by the operators:

The basic objective behind the design of displays is to minimize the fatigue to the operator, who has to observe them continuously. The ergonomic considerations in the design of displays are as follows:

A. The scale on the dial indicator should be divided into suitable numerical divisions like 0-5-10-15 OR 0-10-20-30 and not 0-5-25-35

B. The number of subdivisions between numbered divisions should be minimum.

C. The size of letter or number on indicator is given as Height of letter or number $\geq \frac{\text{Reading distance}}{200}$

D. Vertical figures should be used for stationery dials, while radially oriented figures are used for rotating dials.

E. The pointer should have a knife edge with a mirror in the dial to minimize Parallex Error.

3. Design of hand levers and hand wheels:

The controls used to operate the machines consist of levers, hand wheels, knobs, switches, push buttons and pedals. Most of them are hand operated. When a large force is required to operate the controls, levers and hand wheels are used. When the operating forces are light, push buttons or knob are used. The ergonomic considerations in the design are as follows:

A. The controls should be easily accessible and logically positioned.

B. The shape of the control component, which comes in contact with the hands, should be in conformity with anatomy of human hands.

C. Proper colour produces beneficial psychological effects. The controls should be painted with grey background of machine tools to call for the attention.

4. Lighting, noise and climatic conditions in machine environment:

The working environment affect significantly the man-machine relationship. It affects the efficiency and possibly the health of the operator. The major working environmental factors are:

I. Lighting:

• The amount of light that is required to enable a task to be performed effectively depends upon the nature of the task, the cycle time, the reflective characteristics of the equipment involved and the vision of the operator.
• The intensity of light in the surrounding area should be less than that at the task area. This makes the task area the focus of attention.
• Operators will become less tired if the lighting and colour schemes are arranged so that there is a gradual change in brightness and colour from the task area to the surroundings. The task area should be located such that the operator can occasionally relax by looking away from the task area towards a distinct object or surface. The distinct object or surface should not be so bright that the operator's eyes takes time to adjust to the change when he or she again looks at the task.

II. Noise:

• The noise at the work place cause annoyance, damage to hearing and reduction of work efficiency. Noise caused by equipment that a person is using is less annoying than that caused by the equipment being used by another person, because the person has the option of stopping the noise caused by his own equipment. If the noise level is too high, it should be reduced at the source by maintenance, by the use of silencers and by placing vibrating equipment on isolating mounts. If required, ear plugs should be provided to the operators to reduce the effect of noise.

III. Temperature:

• For an operator to perform task efficiently, he should neither feel hot nor cold. When heavy work is done, the temperature should be relatively lower and when the light work is done, the temperature should be relatively higher.

IV. Humidity and Air circulation:

• At high temperatures, the low humidity may cause discomfort due to drying of throat and nose and high humidity may cause discomfort due to sensation of stuffiness and over sweating in a ill-ventilated or crowded room
• The proper air circulation is necessary to minimize the effect of high temperature and humidity.