Modeling of a capacitive sensor dedicated to drug injection

to follow up patients who inject themselves insulin with injection pen is a quite complex task. Due to the repetition of injections, and the numerous influent parameter the patient can easily made an injection mistake and it is difficult for health-takers to follow these injections and can detect errors. In order to compensate this problem, a device which measures the volume of drug by using electric fields has been developed. A theoretical model, simulations and experiments have been conducted to validate this capacitive measurement technique. The experiments confirm Theory and simulations results. A sensitivity around 5fF for lOuL have been found and a good repeatability between three caps have been achieved which is equal to an error of 0.44fF for lOuL of insulin and correspond to an error of ±4.12%.