The testo 6340 was developed specially for the measurement of differential pressures <50 Pa, such as those occuring in cleanrooms. With the testo differential pressure measurement cell, it is possible to measure differential pressures in this low range, but also to record up to +/- 100,000 Pa differential pressure highly accurately. In the models 6341/6343 with the built-in zero-point calibration, any zero-point drift is eliminated. The magnetic valve mechanism furthermore protects the instrument from overload through short-term pressure peaks.