The Fann Electrical Stability Tester, Model 23E is a portable instrument that measures the electrical stability (ES) of an oil-based drilling fluid. The EST conforms to the electrical stability test procedure that is described in API Recommended Practice for Field Testing Oil-based Drilling Fluids, API RP 13B-2.
The EST includes the meter, electrode probe, 2 batteries, a power cord, 2 calibration standards, and a plastic carrying case.