Direct measurement of air or gas volumes

The high requirements of modern control technology in ventilation systems require an accurate measurement of volumetric flows in air or gases. To be able to do this, the flow sensors must be capable of accurate and quick detection over an extremely broad measuring range from almost zero to the maximum value. The new flow sensors SS 20.250 from SCHMIDT Technology have been precisely designed for this purpose.

An accurate measurement of the volumetric flows and not least its documentation is essential in areas in which people or products are subject to safety requirements or the air conditions must meet certain hygienic requirements. These requirements are not met by simple pressure switches in ventilation systems.

A perfect method of measuring volumetric flows is offered by thermal flow sensors. They allow direct detection of air or gas flows. The particular advantage of this technology is its wide measurement range, completely covering all relevant air and gas flows in air-conditioning technology for cleanrooms or for production processes of comparable requirements. This includes minimum air velocities, such as the ones observed during idle periods, and maximum flows at full load. The striking feature of the so-called thermal anemometry is that it allows easy and accurate measurement and ultimately simple evaluation of the detected data.

Selectively designed for demanding applications

Thermal flow measurement also provides the basis of the newly developed flow sensors SS 20.250 from SCHMIDT Technology. Their complete electronics is housed in a robust metal sensor tube. Their diameter of only nine millimeters makes them the smallest all-rounders of their type. In the air flow, they present minimum resistance and are easy to mount, due to the little space required. For mounting, the accessories include a flange, welding sleeve or through-bolt joints and, of particular interest for cleanroom applications, a wall mounting flange made of stainless steel. For installation in different pipe diameters, sensor lengths of 300 and 500 millimeters are available. The patented dumbbell technology, featuring a high flow angle of radial 360° and axial ±45° can be positioned safely and quickly in the gas flow and does not require accurate alignment in the flow. . In addition to that, the completely seamless design of the sensor head free of undercuts inhibits the adhesion of dirt particles, thus making it easy to clean. If required, the sensors can be delivered with a chemically resistant protective coating. This makes them resistant to aggressive media such as hydrochloric acid, acetone or sulfuric acid, to name just a few, and to reagents present in disinfectants.

The standardized flow rate is detected over a measuring range of 0.06 to 20 m/s. The measuring accuracy of the SS 20.250 is ±5%. High-precision calibration and an ISO calibration certificate guarantee a precision of ±3%. In addition to the flow rate, the temperature of the medium is also measured in quick response.

Apart from their performance features and design, SCHMIDT Technology has also tailored the price of the SS 20.250 to their application range. At a list price of 340 €, the sensors are an adequate solution for applications such as the continuous monitoring of filter units, the control of volumetric flow in extractors or the monitoring of laminar flows in cleanrooms.

Author: Rolf Bürssner, Director of Marketing and Distribution in the Sensor Division of SCHMIDT Technology GmbH in St. Georgen.