DEVELOPMENT OF A SPONTANEOUS POTENTIAL MEASURING EQUIPMENT

Abstract

The developed spontaneous potential (SP) measuring device involves design and construction of non-polarized porous pot as sensing unit, high input impedance preamplifier, using a 24 bits analog- to-digital converter, microcontroller and liquid crystal display (LCD) unit. The non polarizing porous pots were molded using kaolin, clay and sawdust with Aluminum silicate as bound material in the ratio 67:33:1:12 by volume (59.3%, 29.2%, 0.01%, 10.6%). After molding, it was sun dried for 48 hours and later poured water into it for 3 hours and finally oven dried at temperature 150°C for 6 hours during which the added saw-dust was burnt and created the needed porosity and hardened it. Hydrated Copper Sulphate was used as the electrolyte with copper rod as the electrode, and both were put into the porous pot and then sealed off with copper lead points out for connectivity. High input impedance amplifier using Bipolar-Field effect operational amplifier CA3140 was used to design the signal conditioner in a differential mode. The output of the amplifier was fed to the 24- bits high precession analog-to-digital converter, and connected to the microcontroller for processing SP signal measured and display the value on LCD. The developed SP instrument was calibrated by using an available instrument in Geophysics Department, Obafemi Awolowo University, Ile-Ife, Nigeria, and a Mastech Multimeter 69702 model. When compared the reading with available standard the correlation is 0.97 and a deviation of 0.001V with Mastech multimeter when used the two instruments to measure a new AA1.5V ce. The resoution o the deveoped instrument is . with minimum and maximum of -2.48V and +2.48V respectively.