ISA England Section - Technical Articles
Is The Temperature Transmitter market “Dumb” “Clever” or “Smart” ?
Article written by Ron Higginson, Senior Member
of the ISA and General Manager of WE
Instrumentation Limited
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 420mA’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”