Emerson Rosemount 700XA Reference Manual page 25

Reference Manual
2-3-9000-744
The mounting arrangement is designed to ensure integrity of the flameproof enclosure.
The flash chamber block is stainless steel and is surrounded by an insulating mounting
adapter. It houses the heater and a resistance temperature detector (RTD).
The next section houses sample input connections and stem sealing components. There
are two ⅛-in O.D. tubing ports in this section; one port is for sample input, the other is the
exhaust for sample flow.
The flash chamber components are within the enclosure cavity and surrounded with
insulating covers. At working temperatures, the surfaces of these covers become very hot
to the touch.
The tip of the cylindrical flash chamber is the port where the flashed sample is taken to the
oven system. The port near the outer diameter of the end of the heated flash chamber
block is the input for carrier gas.
1.4.6 Methanator
After all other components have been separated from the sample, carbon monoxide and
carbon dioxide, which are normally present in quantities too small to be detected by the
gas chromatograph (GC), can be sent through the optional methanator, where the two
gases are combined with hydrogen to make methane in a heat-generated catalytic
reaction.
The methanator is also known as a methanizer or catalytic converter.
1.4.7 Data acquisition
Every second, the controller assembly takes exactly 50 equally spaced data samples (i.e.,
one data sample every 20 milliseconds).
As a part of the data acquisition process, groups of incoming data samples are averaged
together before the result is stored for processing. Non-overlapping groups of 50 samples
are averaged and stored, and thus reduce the effective incoming data rate to 50/10
samples per second. For example, if N = 5, then a total of 40/5 or 8 (averaged) data
samples are stored every second.
The value for the variable N is determined by the selection of a peak width parameter
(PW). The relationship is
N = PW
where PW is given in seconds. Allowable values of N are 1 to 63; this range corresponds to
PW values of 2 to 63 seconds.
The variable N is known as the integration factor. This term is used because N determines
how many points are averaged, or integrated, to form a single value. The integration of
data upon input, before storing, serves two purposes:
• The statistical noise on the input signal is reduced by the square root of N. In the case of
N = 4, a noise reduction of 2 would be realized.
• The integration factor controls the bandwidth of the chromatograph signal. It is
necessary to match the bandwidth of the input signal to that of the analysis algorithms
in the controller assembly. This prevents small, short-duration perturbations from
Rosemount 700XA
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June 2022
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