A Low Cost Mechanical Anthropometer

Conventional methods used for acquiring used for acquiring anthropometric dimensions in India include measuring tapes and vertical columns, which do not give precise measurements. Though very sophisticated equipment, which have digital displays, are used in the developed countries for body dimension measurements, but are not suitable for out purpose due to high cost. This equipment will facilitate cost effective and precise method of acquiring anthropometric dimensions of Indian populace.

This is an integrated unit facilitating measurement of many dimensions in one go, which is not possible with conventional methods. The precision is better as compare to conventional methods.

The apparatus is mechanical, portable and has the versatility of measurement for entire Indian population.

The main objective of equipment design was to acquire accurate Anthropometric dimensions of farm workers. The cost of the equipment is to be contained within reasonable limit and operation of equipment has to be simple. An attempt was made to make an anthropometer, which is versatile and can measure dimensions in different postures. The purpose was to measure dimensions of farming population, so that equipment and tools can be designed accordingly.

Construction

The apparatus consists of four parts

(a) base plate,
(b) an adjustable seat,
(c) central column with slider,
(d) side assembly for vertical and horizontal measurement.

Base plate is a metallic sheet that supports central column and side assembly. It provides a reference floor for measurement. The subject's feet rest upon the base plate during sitting and standing. The base plate is a rectangular platform made up of mild steel plate (90 x 90 x 1 cm). The one-cm thickness was selected so that there is no deformity while taking measurements over a period of time. The plate was supported on 10 cm diameter camber wheels, to facilitate the movement of the equipment.

A rack and pinion mechanism attached to a vertical column had an assembly for seat attachment. The seat is made up of an angle iron frame (15x15x0.3 cm) and a wooden base (40x20x1.5 cm). It has a backrest of wooden plank (40x8x1.0 cm) mounted on the seat attachment. The seat can be rotated to any side of the vertical column in the horizontal plane to allow space for measurement in standing posture. The rack and pinion assembly also facilitates the lowering and lifting of the seat as per dimensions of the subject. The total travel of rack and pinion is 50 cm. This movement of the seat specifically provides a precise setting of the angle formed at the subject's knees to right angle, allowing the plantar surface of the feet to rest on the base plate. The required height is obtained by rotating a handle of the rack and pinion assembly located at right angle to the seat. The seat can be locked at one position for taking measurement by a lever, located opposite to seat height adjusting handle, which tightens the assembly. The seat can be removed easily by removing the ring on the central column, which is helpful in transportation of the apparatus.

The central vertical column (length =100 cm, diameter 7.5 cm), which is mounted on the base plate with the help of four bolts is made of mild steel rod, a square rod (length =78 cm) mounted on it in the vertical direction on which slider assembly moves. The slider assembly has a horizontal square bar, 200 cm in length distributed equally on both sides. The horizontal bar has 2 sliders on both sides with drop arms of 78 cm. The slider assembly on horizontal bar has telescopic tubes for measurement. Exactly in the same alignment on drop arms, have slider with telescopic tubes for measurement at lower vertical levels with a total travel of 70 cm in vertical direction. The slider of horizontal bar are attached with measuring tapes and any movement gives the value on the measuring tape at the center of the slider assembly at the main vertical bar. The sliders on horizontal bar are useful for measuring arm span whereas drop arm sliders are useful for measuring dimensions like shoulder width, hip breadth, etc. so the slider assembly is capable of measuring any horizontal body dimension at any vertical level for sitting and standing posture.

The side assembly for horizontal and vertical measurement comprises two main components: a vertical slider and a horizontal measuring arm. The whole assembly moves on four rollers, which traverse on two round vertical columns of mild steel 72 cm apart, fixed on base plate. The movement of assembly is controlled by a counter weight (5 kg) which is attached to a nylon rope through arrangements of pulleys. The assembly has a sliding horizontal arm with a telescopic tube. The total slide of the horizontal bar is 100 cm on each side, which also has a measuring tape for measurement. This can measure dimensions like forward reach, leg length, etc. The same telescopic tube of horizontal measuring arm can be used to make any vertical measurement, by moving the complete sliding assembly on rollers at desired vertical height, which is connected with measuring tape. For vertical measurements, measuring tape's one end is fixed to the base plate and other part with the assembly for recording the movement.

The mechanical anthropometer is able to record measurements with tolerable accuracy of 0.5 cm. The cost of the anthropometer at production level will be approximately Rs 10,000 ($ 200). The functional utility serves the purpose of body dimension measurement but with few drawbacks like non-uniform pressure at body parts.
 
Source : Invention Intelligence, May - June 2006