Emerson Rosemount 700XA Reference Manual page 5

Glossary
Auto zero The thermal conductivity detector (TCD) is auto zeroed at the start of a new analysis. The operator can also
configure automatic zeroing of the TCD amplifier to take place at any time during the analysis if the
component is not eluting or the baseline is steady. The flame ionization detector (FID) will auto zero at each
new analysis run and can be configured to auto zero anytime during the analysis if the component is not
eluting or the baseline is steady.
Baseline Signal output when there is only carrier gas going across the detectors. In a chromatogram you should only
see Baseline when running an analysis without injecting a sample.
Carrier gas The gas used to push the sample through the system during an analysis.
CDT Component data table.
Chromatogram A permanent record of the detector output. A chromatogram is obtained from a personal computer (PC)
interfaced with the detector output through the controller assembly. A typical chromatogram displays all
component peaks and gain changes. It may be viewed in color as it is processed on a PC display. Check marks
recorded on the chromatogram by the controller assembly indicate where timed events take place.
Component Any one of several different gases that may appear in a sample mixture. For example, natural gas usually
contains the following components: nitrogen, carbon dioxide, methane, ethane, propane, isobutane, normal
butane, isopentane, normal pentane, and hexanes plus.
CTS Clear to send.
DCD Data carrier detect.
DSR Data set ready.
DTR Data terminal ready.
FID Flame ionization detector. The optional FID may be used in place of a TCD for the detection of trace
compounds. The FID requires a polarization voltage, and its output is connected to the input to a high
impedance amplifier, an electrometer. The sample of gas to be measured is injected into the burner with a
mixture of hydrogen and air to maintain the flame.
FPD Flame photometric detector. The FPD is used to analyze gas compound impurities, such as sulfur,
phosphorous, and metals. When sample gas passes through the hydrogen/air flame the component's
wavelengths emitted are electrically measured. The FPD is located in the analyzer's upper enclosure.
GC Gas chromatograph. The GC is a user-configurable analyzer for various process gas applications.
LSIV Liquid sample injection valve. The optional LSIV is used to convert a liquid sample to a gas sample by
vaporizing the liquid in a heated chamber, so the resulting gas sample can be analyzed.
Methanator The optional methanator, also known as a catalytic converter, transforms the components that are
undetectable by the FID (carbon dioxide and/or carbon monoxide) into methane by adding hydrogen and
heat to the sample.
PC Personal computer.
Response factor Correction factor for each component as determined by the following calibration:
Retention time Time, in seconds, that elapses between the start of analysis and the sensing of the maximum concentration of
each component by the detector.
RI Ring indicator.
RLSD Received line signal detect. A digital simulation of a carrier detect.
RTS Request to send.
Receive data or signal in.
RxD, RD, or S
in
SCS Sample conditioning system.
TCD Thermal conductivity detector. A detector that uses the thermal conductivity of the different gas
components to produce an unbalanced signal across the bridge of the preamplifier. The higher the
temperature, the lower the resistance on the detectors.
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