Pneumatach flow heads

Pneumotach flow heads are also known as Flesich tubes. These electronic transducers have been developed for measuring air flow but may be calibrated for use on other gases. The principle of operation is based on passing the gas through a linear air resistance. A low pressure differential transducer measures the resulting pressure drop which is directly proportional to flow.

By varying the mechanical dimensions of the flow head the full scale of the instrument has been manufactured to be as low as 5 litres/minute and as high as 2000 litres/minute. Larger flow heads are feasible. Full scale pressure drop is nominally 6mb.

The photograph above shows a flow head used in conjunction with a data logger for recording human breath profiles. This configuration can be used as a peak flow meter for patient analysis in medical applications. It has a full scale of 1000 litres/minute. The breathing profiles can be recorded using the Si-Plan profile recorder and recreated on Si-Plan’s breathing simulator.

The flow heads may be calibrated on air, carbon dioxide, nitrogen etc. and can be made for specific applications from stainless steel or plastic as applicable and to customer-specified full scale and pressure ratings.