If a flow transmitter (magnetic type FT) that can measure flow and temperature, then why in some industries people use flow transmitter and temperature transmitter in the same line 1 after another? Even after 1 single flow FT is capable of measuring flow as well as temperature.
I'm aware of few high end flow meters (coriolis) that measure process temperature as well a flow rate, but I'm not aware of a magnetic flow meter that does so. There are magmeters that measure the electronic temperature of the electronics for diagnostics, but the temperature value is really to used for warranty replacement evaluation (to make sure that the failure wasn't due to overheating).
The multimeasurement concept is certainly valid - fewer insertions into the process. As to why a process temperature output is available but is not used but a separate temperature sensor is used, I can only speculate that either the instrumentation designer was just unaware of the availability of the temperature from the flow meter or was subject to the "we've always done it as a separate sensor" philosophy.
In general though, the vast majority of flow meters are just that, flow meters; they are not multivariable meters with a flow output and a temperature output. With the increased use of fieldbus, that's likely to change over the next decade.
Carl Ellis
Measure First
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