Flow measurement instruments with non linear cam transmission - allows accurate readings for low flow rates by means of stepped profile

摘要

The cam is shaped in a non linear helical format and a lever driven by the disc drives the indicator on the instrument. The non linear shape of the disc takes account of the non linear flow law. At the point on the cam corresponding to low flow rates, a series of steps is cut, each step being on the circumference of a different circle concentric with the disc shaft and the inter step contours being radii of those circles. The step size is dictated by the resolution, or smallest reading expected of the instrument. The lever arm is shaped to travel up or down this "staircase" in a discrete manner in the sensitive area, and the main causes of inaccurate readings are removed.