Emerson ROSEMOUNT NGA2000 HFID, Reference Manual

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Reference Manual
748384-C
September 2003
Rosemount Analytical Inc. A Division of Emerson Process Management Analyzer Variables 2-49
NGA2000 Reference
RAW_SIGNAL
Direction Output
Binding None
Type Floating point
Value range Between 0 and 220; typically around 550,000
Units None
Description
The signal from the ADC, filtered by AFT90_ and the median filter if any.
Usage The raw signal from the physical hardware, although filtered. Used to determine
whether the signal is making sense or not, since the user may have calibrated the
analyzer incorrectly. Analyzers with 20-bit ADC's have a typical value on zero gas
around 500,000, whereas the 16-bit ADC in the CLD has an output on zero gas of
around 32,000. A span gas of value close to the MAXRANGE should give a
RAW_SIGNAL of about 800,000 to 1,000,000. Anything else indicates some kind of
problem. At the least, the span gas should give a value significantly different from the
zero gas value, if it does not, there is probably an error in the choice of gases, or the
analyzer physics is inoperable, as for example in the case of a FID whose flame is
out.
See also DET_SIG
REF_DUTY_CYC
Direction Bidirectional
Binding
None
Type Floating point
Value range Typically 0.2785
Units None
Description
CLD only; the temperature compensation offset term
Usage The CLD uses the duty cycle of the sensor block controller to determine the
temperature of the analyzer as a whole. This is used to compensate the PVA value.
This variable is used to provide the offset term in this compensation.
See also
RNGHI
Direction Analyzer: bidirectional; I/0 module: input
Binding RNGHI
Type 4-element floating point array
Value range Between 0 and MAXRANGE
Units ppm
Description
The upper range end points, element 1 being the upper end point for range 1 etc.
Usage The range definition, together with RNGLO. RNGHI cannot be edited higher than
MAXRANGE or lower than MINRANGE using the control module, and should not be
made so through a PC either. It is possible to set the higher ranges of lower value
than the lower ranges, but doing so will confuse any auto-range change algorithm.
The resolution of the analyzer is not directly affected by the choice of range in most
cases, except for the FED which changes a range resistor between certain settings.
However the output resolution is affected, as is the operation of a. linearizer
algorithm.
See also RNGLO
MAXRANGE
MINRANGE