Good Evening all.My question is - For a feed water line to
an equipment if i need to measure the flow we will use
orifice /magnetic/vortex depend on cost/spec.If i need to
measure a ''Alarm''signal and ''Interlock'' from one point
i think we can use orifice type in one location with 2
different tapping points - one for alarm and one for an
interlock to flow valve..If in case i need to have both
these signals(Alarm & interlock) from magnetic flow
meter,is it possible??will 2 seperate sensors will be
located inbuilt r we can program it ??..i thk we can have
one transmitter with these 2 signals...need to know any
technical issues are there?pls clarify
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Answer Posted / carl_ellis
It seems you are using a flow meter's relay(s) to generate
alarm signals at various amplitudes: low, low/low, hi,
hi/hi.
The flow meter doesn't really use these alarm signals
itself, rather it generates the alarm signals and provides
the alarm signals to other devices, for whatever purpose,
alarm, annunciation or an interlock.
There might be a flow meter with 3 alarm relays. I don't
know. That's a shopping issue.
Most places will use a PLC, a controller or a DCS to
generate alarms from the analog flow signal.
But if your flowmeter doesn't have enough relays, then use
a "DC alarm trip" I/O module with the flow meter's 4-20mA
analog output.
The modules have an analog input and one or two relay
outputs with adjustable setpoints. There's probably a
dozen models on this page:
http://www.api-usa.com/signalconditioners_alarms.php
These I/O modules are not used "in a magmeter", they're
external I/O modules.
They place a small burden resistance in the 4-20mA circuit,
need an enclosure and AC or DC power to operate, but they
accomplish the task of providing multiple alarms at various
setpoints.
The 4-20mA signal is wired in series with the I/O module
and any other receiver devices.
Carl Ellis
Measure First
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