Answer / sam

We went through various eras or technology time periods in
instrumentation. Believe it or not but measurements of flow
and level had been done by the old Egyptians that build the
pyramids already. They had use for instants a stick with
marks on it to see what the level was in one of their tanks
and various other simple measuring and control devices as well.

We normally are not to concerned with the type of
instrumentation that was used that long ago. We normally say
that instrumentation only started to take off during the
pneumatic era where all measurement and controls were done
by pneumatic and some electrical instrumentation. The world
standard instrumentation signal was also a pneumatic one
then. It was 20 to 100Kpa or 3 to 15Psi. What this means is
that we had to calibrate our pneumatic pressure transmitters
and controllers to give this output of 20 to 100Kpa. You
really had to know instrumentation when you worked with
these pneumatic stuff. We even had pneumatic relays and
pneumatic chart recorders back then.
Later we moved on to electromechanical instruments and some
very simple electronic indicators and chart recorder.

After the transistor and micro processors were developed
things started to move along very fast and we started to see
various electronic instrumentation and transmitters on the
market. I call this the 4-20mA era. These very advanced type
of transmitters had to be pumped up with a small hand pump
as normal, but all you then had to do was make small
adjustments with a small screwdriver to a zero and span pot
to calibrate the transmitter. Very advanced to what we were
use to. These were called the electronic 4 to 20 mA
TRANSMITTERS.
The new electronic world standard signal then started as the
4 to 20 mA signal, but keep in mind that the pneumatic world
standard signal, even today, is still the 20 to 100Kpa signal.
Since then we have moved on to the smart instrumentation era
where we calibrate the transmitters with a HART communicator
and the transmitter itself is actually a small computer that
can even detect a error on itself or tell you if the
calibration you are trying to do is invalid. From there the
technology of SMART TRANSMITTERS. You even get SMART valve
positioners that can accurately detect the erosion of it's
control valve's plug and seat and send a alarm signal to the
CCR that a overhaul on the valve is needed. All just
computer software and programming like anything else in
today's world. Look what you can do with a cellphone today.
Very smart little gadget.
Not to worry they will never be as smart as a instrument tech.
Good luck

Answer / bala

befoer smart trasmitter had only analog signal
transmission.mostly it was a unidirectional.so that set
value in instrument and some compensation like temperature
drift facility was not available.and also simple wire
interface enough.

but smart tx. having analog and digital communication. with
HART it can be transfer superimposed 4-20ma signal.and it
can be calibrated either local or remote.it's bidirectional
data trasfer is main advandage due to meet control,
calibration, monitoring and link with more than controller.

Answer / purushotham

As its named, it is smart in calibration, diagnostics and communicating.

We have 'Sensor trim' only to correlate between actual PV and sensor generated Digital PV.

And 'Output trim' only to correlate between actual 4-20mA and microprocessor generated Digital PVAO.

We can re-range transmitter any number of times without calibrating the transmitter.

Hence Ranging and Calibration are different tasks here.,

additionally we have remote and local calibration facilities
and very useful diagnostics functions.

Answer / prashant

SMART- SINGLE MODULE AUTO RANGING TRANSMITTER
SMART transmitter are compatible with a Digital
Communication protocol device which is a HART Communicator.
with the help of HART communicator we can share and send the
both Analog & digital Parameter with intelligent or SMART
instruments and also can do on-line calibration with out any
external variables.

only HART protocol device used with SMART transmitter
because of both analog and digital communication.

NON-SMART tx. can not communicate with hart and can not do
like SMART

Answer / kunal

ordinary transmitter means analog pointer transmitter which
has zero and span on tx.but hard to cofigure.

smart tx(Single Modular Addressable Receicer Transmitter)
means digital display and smart to work.

smart tx easily configure by (hht) hart communicator
475,375.

some advanced features like zero,test o/p,simulation of 4-
20 ma.

dignostics message pop up in screen , alarm option.

in mass flow tx showing temp,density,flow,totalizer so many
advanced features enhanced in smart tx.

Answer / dollary

smart transmitter can used without using hart communicator
unlike ordinary smart transmitter you nee hart communicatot
to configure each parameter that you are going to change or
revised.

Answer / vasantharaj

SMART (Single Mode Auto Range Remote transmitters)
instruments are inteliegent instruments, that are
microprocessor based devices, that has set of DDL(Device
Descriptions),in which makes caliberate,rerange,sensor
trim,embedded digital data transmission etc.to be done from
SMART Transmitter through Hand held communicators(like
Emerson 275,372).

Answer / shivu

SMART transmitter will uses the ,HART communicator for the
purpose of Tx-calibration,while the other normal transmitter
needs an extra care at the time of calibration ,bcz in the
normal we have to use the external air supply for the
pressure application ,,,hence it will be gud to have and use
the SMART tx

how can loop single 4-20 ma to two isolation amplifier? i mean i have two isolation amplifier with 4-20 ma input and 1-5 v output.can i done series connection ?

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