Processing Magazine

Air/gas flow measurement for process and plant applications with HART protocol

July 22, 2009
The flow meter series with precision thermal dispersion mass flow sensors and highly intelligent digital electronics is now compatible with the HART communication protocol for use in large-scale process and plant automation systems. HART is a field-proven instrumentation communications protocol that is easy-to-use and provides reliable two-way digital communication without disturbing the integrity of the 4-20mA analog signal. HART communications permit remote process variable interrogation, cyclical access to process data, parameter setting and diagnostics. The flowmeter provides reliable measurement, quick data transmission and interoperability for process and plant engineers in search of a flexible, accurate air/gas flow meter. With two-way HART communications, process and plant engineers have simplified control and access to important ST98 flow data. Diagnostics, calibration and configuration information also are available via HART. With an advanced thermal mass-sensing element, the flowmeter provides rigorous flow measurement over a wide flow range. It features high accuracy to ±1% of reading, plus ±0.5% of full scale. Exceptionally consistent, the unit offers repeatability to ±0.5% of reading. The inline style features an exceptionally wide flow range from 0.00062 to 1850 SCFM in air at standard conditions for 70°F [21.2°C] and 14.7 psia [0°C and 1013,25 bar (a)], typical for most gases. The ST98 offers low-flow sensitivity yet is able to operate from 10:1 to 100:1 turndown ratio and is field adjustable within the calibrated range.