Design of portable instrument for the concentration of potassium ions in human vitreous humor to estimate the postmortem interval

摘要

This paper presents a portable measurement system for the concentration of potassium ions in human vitreous humor. This system mainly consists of three units, which are ion selective electrode, STC89C52 microcontroller and 16-bit AD7705 analog-to-digital convertor. In order to improve measurement precision, temperature compensation was conducted by using DS18B20 temperature sensor to detect ambient temperature and processing data with compensation measures. This system was tested with potassium solution and the precision can reach up to 99.69%. It can measure in situ the concentration of potassium ions in human vitreous humor which can be used to estimate the postmortem interval. The measuring system presented in this paper is easy to operate and can also measure other ions by changing ISE and the value of feedback resistor of operational amplifier.