A method determines an analyte concentration in a sample including the analyte and a substance. The enclosure has sidewalls, a top piece, a back piece and a bottom piece. One buffer is located anterior to the ball joint-post, one buffer is located posterior to the ball joint-post. The front end unit and the public key signature units are preferably individual secure modules with the load balancer being outside the security boundaries. The method also includes enabling a voltage integrator if the target charge voltage is less than the measured battery voltage, and integrating a charge voltage value over time if the voltage integrator is enabled to provide an integrated voltage value. The first chamber communicates with the second chamber via a gap between the second rib and the one sheet of film.