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.
