A hand held spirometer system comprises of a spirometer body and a differential pressure sensor cabinet operationally connected by a communication cable via USB port. The spirometer body has a lower body structure (1) which holds a microcontroller board, an LCD Module, a battery (2) and USB connections (3). Its upper body structure (4) accommodates a TFT colour display (15) and a power on/off switch (14). The differential pressure sensor cabinet has a top part (7) which is joined through suitable fasteners to a bottom part (8) to form the cabinet. The cabinet accommodates a differential pressure circuitry, a differential pressure sensor and a thin film mesh membrane (5) which is placed in cavity (6), sandwiched between the two parts.
