The final output stage of a pressure transmitter is the D/A converter. In the case of the Yokogawa EJA pressure transmitter and the EJX a high precision 15-bit converter is used; therefore, the signal resolution is already very high. Furthermore, HART supports the transmitter variables as 16-bit signed words; therefore, in practice the measurement accuracy remains the same in the HART communication world.

In the case of FOUNDATION™ fieldbus? the story is a little different. FOUNDATION fieldbus uses a 32-bit signed word to represent all Process Variables (PVs) and this represents a huge increase in both accuracy and resolution.

In practice it means that a transmitter no longer needs to be spanned to a customer range: it can be left at maximum span or URL.

Finally, when calibration is required it is enough to calibrate the transmitter at its maximum span or URL.

This is enough to ensure the transmitter's performance at lower ranges or customer defined spans.