It is very difficult to make accurate low pressure measurements  (5 inches of H20 to 15 psig) without taking barometric pressure into consideration. Barometric pressure is not constant as it is a function of atmospheric conditions. Normal Barometric pressure will normally change very slowly in the course of a day.  However, barometric pressure inside a facility can change quickly when an HVAC system cycles on or off, when doors open or close, or when fan turns on or off. Barometric pressure has a large effect on low pressure differential measurements.

The solution for accurate low pressure measurements is to take control of the reference side of the pressure sensor or pressure scanner. There are several things the user can do to control and minimize Barometric changes.

First; place the pressure scanner or pressure transducer in a pneumatically benign location that is not near a fan, doors, or air conditioning systems.

Second: Good practice would be to connect the reference input on the pressure scanner to a static basket (or static bottle) to minimize the potential for measurement errors. This bottle should be mounted somewhere accessible to the reference side of the pressure sensor, or pressure scanner.

The end result is a quiet barometric immune to small changes in the room ambient.

For larger facilities where many pressure measurements are made and multiple static lines may be used, a static basket may be the preferred choice. Multiple reference lines can all be routed to use the same static basket.

Scanivalve offers a pressure static basket and bottle. Details can be found in the drawings located in the downloads section.