Foundation Fieldbus Transmitter Calibration


Fieldbus transmitter ranging software, this time a differential strain transmitter sensing strain dropped throughout an orifice plate so as to infer the speed of flow for fluid contained in the pipe. The transmitter senses small quantities of stress difference (expressed in a unit of stress referred to as inches water column), however what we would like it to report back to the Fieldbus community is an precise flow fee in gallons per minute.

If we occur to know that this orifice plate produces a stress drop of 125 inches water column (125 ”WC) at a flow fee of 350 gallons per minute (350 GPM), we may arrange the scaling parameters as proven:

Fieldbus Flow Transmitter Calibration

Observe using the “oblique sq. root ” L_Type parameter worth as an alternative of simply “oblique” as we used within the ethanol tank instance. The sq. root operate is important on this utility as a result of the connection between differential strain (∆P) and flow charge (Q) by means of an orifice is nonlinear, as described by the next method:

Orifice Meter Equation

This specific non-linearity is exclusive to pressure-based measurements of fluid flow, and doesn’t find utility in another type of course of measurement.

As earlier than, although, we see a typical theme with the XD_Scale and OUT_Scale parameter ranges: we set the XD_Scale parameter to the bodily vary of measurement immediately sensed by the transducer, we set the OUT_Scale parameter to the corresponding vary of measurement we want the transmitter to report back to the remainder of the management system, and we set L_Type to “oblique” to allow this translation from one vary to a different.



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