|
[Instrumentation Table of Contents]
[Sensors and Transducers Suppiers Menu]
The most common type of displacement flow
meter is the nutating disk, or wobble plate meter. A typical
nutating disk is shown in Figure A1.
Figure A1
This type of flow meter is normally used for
water service, such as raw water supply and evaporator feed.
The movable element is a circular disk which is attached to a
central ball. A shaft is fastened to the ball and held in an
inclined position by a cam or roller. The disk is mounted in
a chamber which has spherical side walls and conical top and
bottom surfaces. The fluid enters an opening in the spherical
wall on one side of the partition and leaves through the
other side. As the fluid flows through the chamber, the disk
wobbles, or executes a nutating motion. Since the volume of
fluid required to make the disc complete one revolution is
known, the total flow through a nutating disc can be
calculated by multiplying the number of disc rotations by the
known volume of fluid.
To measure this flow, the motion of the shaft
generates a cone with the point, or apex, down. The top of
the shaft operates a revolution counter, through a crank and
set of gears, which is calibrated to indicate total system
flow. A variety of accessories, such as automatic count
resetting devices, can be added to the fundamental mechanism,
which perform functions in addition to measuring the flow.
|
