This study deals with the development of a nondestructive impedance spectroscopic technique that may assess the conditions of the fruits to pluck them with the help of robotic arms. Preliminary investigations are made with the help of two-terminal probe and an accurate LCR meter. The bulk impedance of mango has been measured to characterise raw and ripe fruits. Effective resistance and effective capacitance vs. frequency characteristics have been determined. The bulk effective resistances, of the ripe fruits, are found to be more than those of the raw fruits, in the frequency range of 1-6 kHz. In the same frequency range, effective capacitances of the raw fruits are found more than those of the ripe fruits. In the light of the data obtained, it can be said that the effective resistance may be used to differentiate between raw and ripe fruits in the frequency range of 1-6 kHz.Keywords Automatic sorting of fruits, electrical impedance spectroscopy, nondestructive testing of fruits, post harvest assessment, quality assessment of fruits.

A portable infrared spectroscopy system has been designed and developed for assessment of quality of mango fruit. This paper describes the design and development of a fruit quality grading device using reflectance mode optical sensor. The experiment was conducted to obtain the best results from the system and the device was correlated according to the measured output. In the experiment, several samples of mango fruits have been monitored for six days to study the relation how fruit quality increases with time as fruit ripens. Between the unripe mango fruit and the ripest one, a range of 3.5 V to 4.2 V was measured by the developed system. The rate of quality increase was calculated as an average of 6.7 mV per day. These results were used to correlate the final hardware and software development of the device. The results demonstrate that, portable near infrared spectroscopy is feasible for evaluating mango quality non-destructively.

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This article presents the details of design and development of a mobile and low‐cost measuring device that can directly measure the thermal conductivity of a material. The device does not need an AC power source and needs only a battery to operate. In its operation, the output of a platinum resistance thermometer (PT100 sensor) is amplified by LM324 Quad differential input operational amplifier and fed to Microchip PIC16F877A microcontroller through an analog‐to‐digital converter. The microcontroller calculates the thermal conductivity of the material by a given set of temperature difference and finally the result is displayed on a liquid crystal display. PIC Basic programming language is used to program the PIC microcontroller. The analog circuit and printed circuit board layout are designed using OrCAD software. It has been observed that the proposed device can measure the temperature with an accuracy of 0.5°C and thermal conductivity with an accuracy of 0.01 W/mm °C. The power consumption of the device is found to be 277.25 mW.