Foundation Fieldbus - Linearization Type

D

Thread Starter

Derrick

Good day! Could I please ask on how to choose between the Foundation Fieldbus linearization type in an instrument whether Direct, Indirect, or Square Root output signal?
 
In most cases if you want to display PV as it is it should be direct...

Like If u have Radar LT and it will directally gives level in MM AI block linearisation type will be Direct...
 
Borrowed from Anderson Instrument's FF transmitter manual (my comments in parentheses)

Direct: By setting to DIRECT, the AI output will be identical to the Transducer Block (configured range and engineering units, for instance mmH2O values from a DP level transmitter) .

Indirect: By setting to INDIRECT, the data supplied by the Transducer Block is applied to any range or calculation parameters established within the AI block. Values between the Transducer Block and the AI Block will remain linear.

(configured scaled values based on the transducer block range, for instance tank volume in liters based to DP mmH2O from DP xmtr and specific gravity)

Indirect Square Root: By setting to INDIRECT SQUARE ROOT, an inferred non-linear value may be generated by AI block. This would be commonly used for correlating a differential pressure measurement to the corresponding flow rate in a line.

http://andinst.com/PDFs/2036.pdf (page 12 pdf)

Rosemount has a good explanation on page 22 (pdf); Foundation Fieldbus Blocks, 00809-0100-4783, Rev. BA
http://www2.emersonprocess.com/siteadmincenter/PM Rosemount Documents/00809-0100-4783.pdf

or here: http://tinyurl.com/oqqcjnx

National Instruments has a page on FF AI scaling here:
http://www.ni.com/white-paper/3537/en/
 
D

Derek Rafols

Thanks to all your posts! One last question, does it mean that I have a Direct signal conversion if the transducer range is at for example -1 to 2 bar, and the DCS range at -1 to 1 bar?
 
Top