Badger Meter Vortex Meters - Manual (Page 3)

Form No. 09-VRX-UM-00007 1
INTRODUCTION
DESCRIPTION
The RVL series vortex-shedding flow meter is a general-purpose electronic liquid flow meter. Three
outputs are available. The standard output is a two wire (loop powered) 4-20 mA current. Options for a 0
to 5 VDC or a frequency output proportional to the volumetric flow rate are also available. The choice of
output must be made at the time of ordering. High accuracy is assured by individual flow testing. Since it
uses no moving parts, maintenance is minimized.
The RVL is available in several types of plastics allowing them to be used in a wide variety of chemical
applications.
OPERATING PRINCIPLE
An everyday example of a vortex
shedding phenomenon is a flag
waving in the breeze: the flag
waves due to the vortices shed by
air moving across the flagpole.
Within the flow meter, as a fluid
moves across a tiny strut or “bluff
body”, vortices are also shed but
on a smaller scale. The vortices
form alternately, from one side to
the other, causing pressure fluctuations. These are detected by the crystals in the sensor tube, and are
converted to an analog signal or pulse output. The frequency of the vortices is directly proportional to
the flow. This results in extremely accurate and repeatable measurements with no troublesome moving
parts (see figure 1).
FLUIDS
Any clean liquid compatible with the plastic material of construction that does not contain significant
amounts of fibers or abrasive materials can be used.
Danger - Do not use with: explosive
or flammable materials, food or bev-
erages, or gaseous fluids.
Viscosities above 1 cSt will raise the minimum
usable flow rate (in effect reducing range-abil-
ity). This effect is linear to viscosity. No adjust-
ments are required for viscosities up to 2.0 cSt.
Liquids with higher viscosities will adversely
affect the permissible amount and duration of
over range flow (see table 1).
Viscosity and Rangeability
Viscosity Minimum Maximum Flow Range
1 cSt 1 12 12:1
2 cSt 2 12 6:1
3 cSt 3 12 4:1
4 cSt 4 12 3:1
5 cSt 5 12 2.4:1
6 cSt 6 12 2:1
TABLE 1
Bluff
Body
Counter
Detector
Detector
FIGURE 1