Glossary
35
impedance . . . . . . . . . . . . . . . the ratio of voltage to current at a specified frequency measured in
Ohms, a resistor of the same value would act the same as the mea-
sured circuit
in-situ . . . . . . . . . . . . . . . . . . measurement with sensor located in the process stream
intrinsically safe . . . . . . . . . . incapable of releasing enough electrical or thermal energy to cause
the ignition of flammable substances listed for a hazardous area
classification
LBS H
2
O/mmscf. . . . . . . . . . see - pounds of water per million standard cubic feet
LCD . . . . . . . . . . . . . . . . . . . Liquid Crystal Display - a display that uses a special material [that
is sensitive to electrical voltages] to affect the transmission or
reflection of light
monograph . . . . . . . . . . . . . . a systematic learned exposition of a subject, e.g. a chart represent-
ing dewpoint conversions for differing pressures.
National Electrical Code. . . . a set of US standards related to accepted practices for electrical wir-
ing
NFPA. . . . . . . . . . . . . . . . . . . National Fire Protection Agency (issuer of the National Electrical
Code (NEC))
NIST . . . . . . . . . . . . . . . . . . . National Institute of Standards and Technology
NPT . . . . . . . . . . . . . . . . . . . . National (American Standard) Pipe Taper; an ASTM (American
Society for Testing and Materials) standard of tube fittings with
tapered threads
parity . . . . . . . . . . . . . . . . . . . a way of incorporating error checking into a RS232 data transmis-
sion [on a character by character basis] to check if the data has been
received correctly
pounds of water per
million standard cubic feet . (LBS H
2
O/mmscf) the mass of water vapor present in unit volume
of moist air at standard temperature and pressure.
a measurement unit for moisture, typically used in the natural gas
industry
ppm . . . . . . . . . . . . . . . . . . . . parts per million - usually based on volume measure, but must be
stated whether it is by volume or by mass (weight)
ppmV . . . . . . . . . . . . . . . . . . parts per million based on volume measure, volume of water vapor
per total volume of gas for an ideal gas.
pressure correction . . . . . . . . computation of dewpoint at a pressure different from the pressure at
the sensor
PROM . . . . . . . . . . . . . . . . . . Programmable Read Only Memory - a device that can be pro-
grammed so that data is permanently stored in it [typically used for
computer programs]
RAM . . . . . . . . . . . . . . . . . . . Random Access Memory - a device that holds data as long as it has
power applied to it [the data can be changed with out limit]
regenerative dryer purge . . . . small flow of dry air from drying column passing through regener-
ating column and desorbing water from desiccant at low pressure
response time . . . . . . . . . . . . time it takes for a sensor to react to change in its environment
RG58. . . . . . . . . . . . . . . . . . . a type of coaxial cable - the letters/numbers refer to the electrical
characteristic of the cable [resistance/capacitance per foot of
length]
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