Abstract: Reference electrodes for potentiometric measurement of pH and ion concentration typically use mercury calomel or silver/silver chloride element combined with a saturated solution of potassium chloride (KCl) for the development of a stable potential with respect to a sensing electrode when immersed in solution. The salt KCl is preferred because of it is almost equitransferent and thus minimizes the diffusion potential set up between the reference solution and the solution being tested. However, reference electrodes using concentrated solutions of KCl suffer a drawback, which is its propensity to develop a creeping salt discharge that rapidly covers surfaces with KCl crystals. This “salt creep” phenomenon appears to be unique to KCl; Salt creep is a major nuisance, particularly for reference electrodes used on semi-dry surfaces such as skin.

Abstract: A portable electronic device is disclosed. The device has a first program stored in memory contained within the device and a second program stored on transposable memory which is releasably connectable to the device. The transposable memory comprises a plug-in module having a EEPROM. The second program stored on the transposable memory comprises a series of groups of instructions which are downloaded, as required, by the device and executed in order. The specific groups to be downloaded are determined by a jump table which accesses different groups of instructions in response to input signals. The instructions to be downloaded are identified by variable addresses in the jump table, and, the variable addresses are updated by means of the first program and the second program.

Abstract: A method and apparatus for predicting the fertility status of a human female subject. The onset of menstruation of the subject is noted. Daily determinations are made of the subjects eccrine sweat pH, beginning not more than 4 days following menstruation. The start of the fertile period is determined as a function of a significant decline in pH, followed by a sharp rise. The peak of this pH rise is indicative of imminent ovulation, which generally coincides with a second pH decline of variable degree. The apparatus provides provisions for automatically taking the pH readings, analysing them, and displaying to the user the daily fertility status.