Measuring Principle

 

Orifice plates, nozzles and Venturi tubes

This kind of differential-pressure flowmeters contain an artificial constriction (e.g. an orifice, a nozzle or a Venturi tube). As soon as the fluid starts flowing, the natural laws governing the mechanics of flow dictate that pressure upstream of the constriction increases, only to drop again immediately downstream of the constriction. The pressure differential is a direct measure of the flow rate.

 

Pitot tube

This method uses a rod-like primary element. Pressure tappings are located on the front and rear of this probe. The upstream tappings register dynamic and static pressure, the downstream tappings register only static pressure. The differential pressure is a direct measure for the flow rate.

 

Advantages

Time proven robust technique

Wide range of line sizes

Easy installation

No process interruption for exchanging transmitters

Broad choice of materials

Wide turndown

Ceramic, self-checking sensor

Wide temperature and pressure range

Very high repeatability