Modification and Performance Evaluation of a Portable Hand-Held Refractometer
Abstract:
The portable hand-held refractometer was modified, fabricated and its performance was evaluated. The modified refractometer consists of six main parts which include adjustment focus, calibration point, light cover, magnifying eye piece, bi metal strip and primary prism. Hand held refractometer was modified by incorporating a metallic strip and Charge-coupled Device (CCD) sensor, which measure high total soluble solid and also correctly deter mines the intensity of the light reflected and also the exact critical angle that reflect the light completely. A few drops of water will be placed on the prism surface for cleansing and calibration. The light cover will be closed and the refractometer will be holding on the direction of light source and the scale will be set to zero by using calibration point and looking through the magnifying eye piece. The modified refractometer has been compensated automatically for the temperatures of the samples. The actual tests were conducted using samples of water melon, cashew and mango juices at certain levels of pH values. The average percentage Brix values of water melon, ca shew and mango juices are 7.47%, 13.20% and 13.50% respectively. It was observed that mango juice has highest percentage Brix than water melon and cashew juices. This means that it can deteriorate faster than other two juices. The analysis of variance (ANOVA) for the effect of temperature and pH used for the experiment show that F-calculated (3.883) is greater than F-table (3.35) at 5% probability level; therefore, the conclusion is that at least one of the treatment means is difference. It appears that the rate of pH or temperature sensitivity of the modified refractometer used could not be the normal rate for the experiment
