Development of an Automatic Body Mass Index Measurement Machine

Abstract

The potential occurrence of certain illnesses can be easily diagnosed through measurements of some health indicators. One of such parameters is the Body Mass Index (BMI). BMI is simply the ratio of mass (kg) of a body to the square of its height (m2 ). This research presents the design and construction of an automated BMI measurement machine for medical purposes. It consists of three major units: the weighing unit (5 – 200 kg); height-measuring unit (0.02 – 2 m) and the processing unit. The weighing unit is made up of load button cell and load cell amplifier while the height-measuring unit consists of ultrasonic sensor. The analog differential output voltage from load cell is connected to Arduino microcontroller via a Programmable Gain Amplifier (PGA) integrated with Analogue-to-Digital Converter (ADC). The two units are connected to an open source Arduino Uno which computes mass-to-body ratio and sends the output results (mass, height and BMI) to the liquid crystal display (LCD). The weighing system was calibrated against a precision digital weighing system and it gave a correlation of 0.99. The height measurement was also compared with manual height measurement using a tape rule which gave a correlation of 0.97. The developed Instrument is cost effective and has high positive correlation with the standards (weighing scale and tape rule), it is therefore recommended for the measurement of weight, height and BMI.