A device (100, 200) for determining at least one pulmonary function characteristic, the device (100, 200) comprising: (i) at least one chamber (110, 210) comprising at least one gas inlet port (120, 220), configured to receive gas flow; a distal element (240, 440, 540) comprising at least one distal opening (446, 546); at least one pressure transducer (126, 226) configured to detect pressure within the at least one chamber (110, 210) and to produce a signal upon detecting pressure at about a predetermined threshold; (ii) at least one shutter module (150, 250, 450, 550) connected to said distal element (240, 440, 540), said at least one shutter module (150, 250, 450, 550) comprising at least one shutter opening (152, 154, 456, 556); (iii) an actuator configured to displace, or induce displacement, of the at least one shutter module (150, 250, 450, 550) upon receiving the signal, or a signal derived from said signal, wherein the actuator is a rotary actuator and the shutter module (150, 250) is a shutter wheel (450, 550) having a circular form, and wherein the actuator is configured to displace, or to induce displacement of, the at least one shutter wheel (450, 550) by rotation; (iv) a control system configured to acquire pressure data from the at least one pressure transducer, and to process said data, and (v) a shutter pin (276, 426, 576) and a hard stop (270, 470, 558) comprising a groove, wherein the shutter pin is located within the groove, and wherein the shutter pin (276, 426, 576) is configured to limit the range of displacement of the shutter module (150, 250, 450, 550); wherein the at least one shutter opening (152, 154, 456, 556) is configured to allow passage of gas flow from the at least one distal opening (446, 546) to the atmosphere through a first total effective area (A S1) enclosed by a perimeter of the at least one shutter opening (152, 154, 456, 556), when the shutter module (150, 250, 450, 550) is in a state of first end position; and wherein upon said displacement the first total effective area changes to a second total effective area (A S2), when the shutter module (150, 250, 450, 550) is in second end position, wherein the second total effective area (A S2) is always a positive value. (i) at least one chamber (110, 210) comprising at least one gas inlet port (120, 220), configured to receive gas flow; a distal element (240, 440, 540) comprising at least one distal opening (446, 546); at least one pressure transducer (126, 226) configured to detect pressure within the at least one chamber (110, 210) and to produce a signal upon detecting pressure at about a predetermined threshold; (ii) at least one shutter module (150, 250, 450, 550) connected to said distal element (240, 440, 540), said at least one shutter module (150, 250, 450, 550) comprising at least one shutter opening (152, 154, 456, 556); (iii) an actuator configured to displace, or induce displacement, of the at least one shutter module (150, 250, 450, 550) upon receiving the signal, or a signal derived from said signal, wherein the actuator is a rotary actuator and the shutter module (150, 250) is a shutter wheel (450, 550) having a circular form, and wherein the actuator is configured to displace, or to induce displacement of, the at least one shutter wheel (450, 550) by rotation; (iv) a control system configured to acquire pressure data from the at least one pressure transducer, and to process said data, and (v) a shutter pin (276, 426, 576) and a hard stop (270, 470, 558) comprising a groove, wherein the shutter pin is located within the groove, and wherein the shutter pin (276, 426, 576) is configured to limit the range of displacement of the shutter module (150, 250, 450, 550);