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OTHER FLOW METERS
Hot-Wire Anemometer

Instrumentation and Control Volume 1 of 2
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Flow Detectors OTHER FLOW METERS The float should stay at a constant position at a constant flow rate.    With a smooth float, fluctuations appear even when flow is constant.   By using a float with slanted slots cut in the head, the float maintains a constant position with respect to flow rate.   This type of flow meter is usually used to measure low flow rates. Displacement Meter In  a  displacement  flow  meter,  all  of  the  fluid  passes  through  the  meter  in  almost  completely isolated quantities.   The number of these quantities is counted and indicated in terms of volume or weight units by a register. Nutating Disk The most common type of displacement flow meter is the nutating disk, or wobble plate meter.   A typical nutating disk is shown in Figure 7. Figure 7   Nutating Disk 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. Rev. 0 Page 9 IC-04







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