SCHMIDT® flow sensors SS 20.400 and their ATEX counterpart SS 23.400 detect very small air flows down to 0.05 m/s. Moreover, they have an integrated direction detection. Installed additionally for pressure measurement, the bidirectionally working flow sensors can reliably detect the existing overflow in cleanrooms or clean areas. If backflows take place, resulting in contamination, this is also reliably detected.
Upon request, the sensors can be supplied with high-precision adjustment. It provides a further improvement in the accuracy by the increased number of adjustment points and documentation of the nominal and actual values as ISO calibration certificate. The measuring accuracy is ±1% of the measured value plus 0.04 m/s.
For laminar applications, the sensors are now adjusted in a vertical flow channel. Its setup guarantees a falling air flow, as ideally required in practical application, and excludes all external influences from actual measuring practice. This also takes into account the so-called thermal convection flow, which in practice amounts after all to about 10% of the downdraft flow of 0.45 m/s.
The ATEX version SS 23.400 for use in hazardous areas meets the ATEX Directive 94/9/EC. The flow sensors are DEKRA-certified and can be used in Zone 2 (device category 3G) without any additional measures, such as a zener barrier.
The functioning of the bidirectional measurement with thermal flow sensors is described in a brochure that can be downloaded here.
Source: SCHMIDT Technology GmbH