Appendix G Glossary
146 | 266 MODBUS® multivariable transmitter User manual 2105216 Rev. AB
Appendix G Glossary
Asea, Brown and Boveri, parent company of Totalflow
is zero-referenced against a vacuum, so it is equal to gauge pressure plus atmospheric pressure
how closely a measured value agrees with the correct value. It is usually expressed as ± percent of the
full scale output or reading.
a unique memory designation for the location of data or the identity of a peripheral transmitter. It allows
each transmitter on a single communications line to respond to its own message.
American Gas Association. Trade group representing natural gas distributors and pipelines
American Gas Association Report No. 3.
AGA3 1985 (wet gas), Orifice Metering of Natural Gas and Other Related Hydrocarbon Fluids. Method
for calculating gas volume across an Orifice Plate. This method requires two pressure readings:
Differential Pressure (DP) and Static Pressure (SP).
AGA3 1992, Orifice Metering of Natural Gas and Other Related Hydrocarbon Fluids. Addresses
standards for flow rate, orifice diameter and differential pressure.
Part 1-General Equations and Uncertainty Guidelines
Part 2-Specifications and Installation Requirements
Part 3-Natural Gas Applications
AGA3 2012, Orifice Metering of Natural Gas and Other Related Hydrocarbon Fluids. Revision of Part 1-
General Equations and Uncertainty Guidelines. It gives equations and guidelines for computing flow
through orifice meters.
11
an electric current whose direction changes with a frequency independent of circuit components
the temperature of the air, atmosphere or other fluid that completely surrounds the apparatus, equipment
or work piece under consideration. For devices which do not generate heat, this temperature is the same
as the temperature of the medium at the point of device location when the device is not present. For
devices which do generate heat, this temperature is the temperature of the medium surrounding the
device when the device is present and generating heat. Allowable ambient temperature limits are based
on the assumption that the device is not exposed to significant radiant energy sources such as sunlight
or heated surfaces.
a system in which data is represented as a continuously varying voltage/current
a communications protocol where information can be transmitted at an arbitrary, unsynchronized point in
time, without synchronization to a reference time or clock
term used for the European Union’s New Approach Directive 94/9/EC which concerns equipment and
protective systems intended for use in potentially explosive atmospheres
a unit of pressure. The pressure that will support a column of mercury 760 mm high at 0 °C.
the pressure exerted on the earth by the earth’s atmosphere (air and water vapor). A pressure of 760
mm of mercury, 29.92 inches of mercury, or 14.696 pounds per square inch absolute, is used as a
(scientific) standard for some measurements. Atmospheric pressure may also refer to the absolute
ambient pressure at any given location.
A bar is equal to 1 atmosphere of pressure, 0.987 standard atmospheric pressure or 14.504 PSIA.
the pressure used as a standard in determining gas volume. Volumes are measured at operating
pressures and then corrected to base pressure volume. Base pressure is normally defined by a gas
measurement contract. The standard value for natural gas in the United States is 14.73 PSIA,
established by the American National Standards Institute as standard Z-132.1 in 1969.
unit of signaling speed. The speed in baud is the number of discrete conditions or events per second. If
each event represents only one bit condition, baud rate equals bits per second (bps).
serial communications data transmission rate expressed in bits per second (b/s)
This adapted text summarizes abstracts of AGA Report No. 3, Report No. 5, Report No. 7, Report No. 8, and PRCI NX-19.
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AGA – All rights
reserved.
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