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Flow computers, totalizers and indicators can integrate
the functions of flow and temperature measurement, flow
computation, alarms, data acquisition, input / output calibration,
and closed loop flow control. They require external sensor
input to function. In addition, they may also be used as
local rate indicators.
Flow computers, totalizers and indicators can be used to
measure gas, liquid or flow of mixed phases such as steam.
Flow
computers can interface with a number of different sensors,
including differential pressure meters, velocity meters
and true mass meters. These instruments can display flow
values in a number of different ways. Volumetric flow rate
shows how much of the measured medium passes through the
sensor. Velocity flow rate shows the speed of the medium.
Mass flow rate shows the weight or mass of the medium and
might be displayed in units of pounds per minute or a similar
unit.
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Displays
for flow computers can be simple analog indicators, digital
numeric or alphanumeric displays, or video display terminals.
Interfaces for controlling flow computers likewise can be
analog, with switches, dials and potentiometers; digital with
menus and keypads; or computer control through parallel or
serial interfaces. Analog outputs can be voltage, current,
frequency or switched.
Flow computers, totalizers and indicators can mount directly
on the flow sensors they work with. They can also sometimes
be mounted on a wall, an instrument panel, a rack, or DIN
rail. They can also be portable or benchtop instruments, as
might be used in a laboratory. Flow computers, totalizers
and indicators can have sanitary ratings for use in food,
pharmaceuticals and other processes. They can have recorder
functions and can be used as controllers, providing control
function such as limits, PID or logic and outputting control
signals. They can be programmable and have built-in alarms. |
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