Michał Jakubowicz

Air Gauge Characteristics Linearity Improvement

This paper discusses calibration uncertainty and linearity issues of the typical back-pressure air gauge. In this sort of air gauge, the correlation between the measured dimension represented by the slot width and the air pressure in the measuring chamber is used in a proportional range. However, when high linearity is required e.g., nonlinearity less than 1%, the measuring range should be shortened. In the proposed method, based on knowledge of the static characteristics of air gauges, the measuring range is kept unchanged but the nonlinearity is decreased. The static characteristics may be separated into two sections, each of them approximated with a different linear function. As a result, the nonlinearity is reduced from 5% down to 1% and even below.

Influence of the Inlet Nozzle Diameter on the Air Gauge Dynamics

In the paper, the experimental results of the study on the dynamic characteristics of the air gauges are presented. Dynamical properties of the air gauge are dependent mainly on the pressure transducer type and also on the geometry of its flow-through elements. The present investigations focused on the diameter of the inlet nozzle and its impact on the time constant and the frequency at which the dynamic error would not exceed 5%. It was proved that in the most common configurations of the air gauges, those two parameters may vary up to 100%, and the dynamics of the air gauges worsened with smaller inlet nozzles. The results are of high practical importance in industrial measurement systems where the air gauges are applied, because the multiplication of the air gauge is typically set by the adjustment or replacement of the inlet nozzle.