DESCRIPTION AND USE
Cox Precision Turbine Flow Meters are a precisely manufactured and calibrated instruments used in accurate rate-of-flow and
total-flow measurement of all types of fluids, whether liquid or gas .
They also have many applications as sensors in process flow control .
The flow meter mounts directly in the flow line and consists of a cylindrically bored housing, a flow straightener and turbine
assembly, and magnetic or carrier frequency pickoffs, as shown in
On all Precision Flow Meters, the magnetic or carrier frequency pickoff is located directly above the turbine, near the
downstream end of the flow meter . The flow straightener and turbine assembly is retained in the housing by a snap ring and
can be easily removed for cleaning and further disassembly .
Figure 1: Turbine flow meter
Cox Precision Turbine Flow Meters are provided with flow straighteners at the downstream and upstream ends . The flow
straighteners diminish any turbulence created by the turbine . Other physical differences are illustrated in exploded views . See
and
.
Fluid passing through the meter causes the rotor and bearing to revolve at a speed directly proportional to fluid velocity .
As each rotor blade passes the pickoff, it varies the pickoff’s reluctance, producing an output signal . Since turbine speed is
directly proportional to fluid velocity, signal frequency is similarly proportional to the volumetric rate-of-flow . The output
signal can be fed into various types of instruments to indicate the rate-of-flow, such as indicators, frequency converters,
counters, recorders and controllers .
Cox uses two pickoff technologies, magnetic and carrier frequency (RF) . The magnetic pickoff has a self-generating mV
frequency output . The RF carrier pickoff senses eddy current losses as the rotor blade passes the pickoff . It does not use an
internal permanent magnet and therefore eliminates magnetic drag on the rotor . This results in linear flow ranges up to 100:1
and repeatable operating flow ranges up to 150:1 . The RF carrier pickoff requires a signal conditioner to generate an output . A
high level signal offers the advantage of high output signal to noise ratio over the entire range of the flow meter and permits
long distance signal transmission .
All Cox Precision Turbine Flow Meters are designed to provide a high frequency output voltage at the maximum of their
flow range . This high frequency signal improves resolution and standardized output permits several overlapping range flow
meters to be connected in series to one indicating instrument . Data concerning extended ranges, specific output voltage
and other frequency ranges is available from the Badger Meter Sales Department . As with any precision instrument, the full
capabilities of the Cox Precision Turbine Flow Meter can be realized only through close adherence to the installation and
maintenance instructions discussed in this manual .
User Manual
Page 5
May 2014
