Standard data is a form of work measurement that consists of time values for specific elements of work. The manual part of a task is broken down into groups of hand motions or body motions that can be precisely defined and that are applied only in connection with a particular machine or a specific operation. The elemental time values usually take the form of tables, formulas or graphs. Elemental time values for establishing standard data had been determined by stop watch time study until determined time systems became available. Through simple plans for combining motions into “elemental building blocks” and the further combination of these data, Deere & Company has developed a system of ”Operational Data” which they have used successfully over a period of years.
The Deere plan consists of four parts of steps:
1) Predetermined time system (micro-motion time)
2) Basic data (combination of predetermined times for motions)
3) Universal data (A combination of blocks of basic data)
4) Operational data (Time values for elements for a specific type of operation).
Physiological Methods of Measuring Work:
Physical work induces changes in oxygen consumption, heart rate, pulmonary ventilation, body temperature, and lactic acid concentration in the Blood. Although some of these factors are only slightly affected by muscular activity, there is a linear correlation between heart rate, oxygen consumption and total ventilation, and the physical work performed by an individual.
Of these three, heart rate and oxygen consumption are the most widely used for measuring the physiological cost of human work. When a person is at rest, heart rate and the oxygen consumption are at a fairly steady level. Then when the person does muscular work i.e. when he changes from a resting level to a working level both the heart rate and the oxygen consumption increase. When work ends, recovery begins and the heart rate and oxygen consumption return to the original resting level.
Heart Rate Measurement:
For example a graph may show that initially the heart rate was 70 beats / min, and when the individual started working it gradually increased to 110 beats / min and when he stopped working heart beat dropped off gradually to 70 beats/ min. The increase in heart rate during working may be used as an index of the physiological cost of the job. The total physiological cost of a task consists not only of the energy expenditure during work, but also the energy expenditure above the resting rate during the recovery period, i.e. until recovery is complete:
Each time the heart beats, a small electric potential is generated. By placing electrodes on either side of the chest, this potential can be picked up and transmitted by wire or radio transmitter to a receiver. There are individual heart beats that can be counted directly, or by means of a cardio-tachometer the impulses can be converted into the heart rate. This data can be continuously on ruled graph paper by milli-ampere recorder.
Heart beat signals can also be obtained by means of an ear lobe unit. Information concerning rate of recovery also can be obtained simply by using a stethoscope and stop watch.
Portable Heart Rate Recorder:
A compact, lightweight, two lead heart rate recorder which records signals up to 26 hours can be worn by the worker. This unit has a synchronous motor drive, integrated circuit and a rechargeable battery pack. An event marker button, when depressed by the worker records an event mark on the tape for precise time / event correlation.
An automatic tape scanning system, called Electro-cardio scanner, permits the recordings to be played back at real time recorded speed or at rapid speeds of 30, 60, or 120 times real time. Heart rate is known as a trend line on oscilloscope and is automatically printed on a summary trend chart.
Measuring Oxygen Consumption:
Change in the rate of oxygen consumption from the resting level to the working level is also a measure of the physiological cost of the work done.
A person extracts oxygen from the air breathed. In order to measure oxygen consumed per unit of time, it is necessary to measure the volume of air exhaled and the oxygen content of this air. Oxygen consumption may be defined as the volume of oxygen expressed in liters per minute which the individual extracts from the air inhaled. A common method of obtaining this information is by means of a portable respirometer.
A respirometer is a light wt. (5½ pounds) gas meter which can be worn on the back. The person is equipped with a mask and a 1 inch rubber tube which carries the air from the mask to the respirometer. This respirometer indicates directly the volumes of exhaled air in litres. A sample of the exhaled air is drawn off at random intervals into a rubber football bladder, and an analysis of its content is made. This permits a comparison of the oxygen content of the sample of expired air with that of air in the room.
A curve can be drawn showing energy expenditure before, during and after physical work.