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The days have long gone where every
temperature measurement has compensation cable, for
thermocouples (T/C ) and 2, 3, & 4 wire cable, for
resistance bulbs ( RTD ) running from the point of measurement all the way back to the control
room or instrument panel. Today and for the past few years a
temperature transmitter now resides in the T/C or RTD connection
head, transmitting the traditional 4-20mA’s or now a selected
“Protocol”.
The
first breed of these transmitters can now be deemed as “Dumb” as they are fixed range, calibrated and ranged during
manufacture, never to be changed. Even today these transmitters
are still available, but represent less than 10% of the UK
market place.
A
new generation of transmitter emerged that could be programmed
after manufacture and with the appropriate software can even be
programmed on site. I would classify these by today’s
available technology as “Clever”, as they can be programmed for every type of T/C or RTD,
needing only one model to cover all eventualities. The number of
units sold commanding 65% of the market place despite only
having communication in one direction.
The
latest bread, “all singing and all dancing” with
communication in both directions are definitely “Smart”.
These transmitters provide much more, when used for the right
reasons. Representing the rest of the available market for the
T/C and RTD transmitters these devices provide full “Smarts”
communicating all their details via HART, Fieldbus , Profibus
etc.
Although,
“Smart”
transmitters are the latest and the greatest, for the total
number of units sold in the UK, the “Clever”
is still king. The comparative cost of these two devices is that
the “Smart” is
nearly three times more expensive than the “Clever”.
So,
it would appear that
“Smart
engineers are buying Clever
transmitter”
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