Ranarex Gravitometer0 pages

CHANDLER ENGINEERING

®

PROCESS INSTRUMENTS

Ranarex™ Gas Gravitometer

Ranarex Portable Gravitometer from AMETEK Excels in Total Performance
Features
►t tAccurate
t Eliminates span drift to ensure
permanently accurate calibration.
►tSensitive
t Advanced design develops large
measuring forces and is virtually
friction-free.
►t Fast Response
t Gas sample flows continuously
at a high rate through a small
measuring chamber that purges
rapidly.
►tRugged
t Durable, corrosion-resistant
materials. Outer case protects
against dust, humidity, and
shock.
►t Low Cost
t Simple design for low equipment
cost; simple piping and wiring
for low installation cost; rugged
construction for low maintenance
cost. These features ensure
lowest long-term, total cost.
►t Easy to Use
t Completely mechanical and
easily understood. Installation
requires only piping or tubing
and electrical power. No special
skills required.
►tReadable
t Indicating scale is 6” wide. Can
be read from a distance.

Operation

The Ranarex principle and design
are simple. The chassis of the
gravitometer forms two cylindrical,
gas-tight measuring chambers; each
has a separate inlet and outlet connection. In each chamber there is an
impeller and an impulse wheel, both
with axial vanes. These wheels are
mounted on separate shafts, facing
each other but not touching. An
electric motor and drive belt rotate
the impellers at the same speed and
in the same direction. The impellers
draw continuous flow of gas sample
into the upper chamber, and reference air into the lower chamber.
They spin the gas and air against
the vanes of the corresponding
impulse wheels. As the spinning gas
and air impinge against the vanes,
they create torques on the impulse
wheels that are proportional to the
density of the gas and of the air.

Specific Gravity
These torques are transmitted
from the chambers to two external
measuring wheels. A flexible tape
is wrapped on the measuring wheel
rims in the crossed direction so that
the torque creates two opposing
forces. The measuring wheels are
restrained from continuous rotation, but a difference between the
torques allows limited motion of
the entire system. The measuring

system divides the torque of the
gas by the torque of the air. This is
the same ratio as the density of the
gas divided by the density of the air
which is —the specific gravity.
The rim of the gas measuring
wheel is contoured so that it rotates
through equal angles for equal
changes in specific gravity. The
uniform motion of the gas measuring wheel is transmitted by a link to
the readout indicator.
To ensure accuracy, the gas sample
and the reference air must be
measured at ambient temperature,
at barometric pressure, and at equal
humidity content (either humidified
or dry).

Portable Gravitometer
No elaborate setup is required for
the portable version. The unit can
be operated from the floor, a bench,
or hung from the wall and operated
from a standard AC power supply
or from a 12-Volt vehicle battery
through a DC-AC inverter.

Ranarex gravitometers excel over more
complex and costly analyzers in total
performance.

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