Reference Manual
748384-C
September 2003
Rosemount Analytical Inc. A Division of Emerson Process Management Analyzer Variables
2-51
NGA2000 Reference
SIGNAL_GAIN
Direction
FID: Output; CLD: bidirectional.
Binding
None
Type
FID: 2-element enumerated array; CLD: integer
Value range
FID: LOW; MEDIUM; HIGH; CLD: 1 - 64
Units None
Description
NDIR only; determines the analog signal gain
Signal gain of final resistor divider chain (FID).
Signal gain of preamplifier (FID).
CLD only: signal gain of PGA.
Usage
FID only; these are set by a combination of CARBON_ATOMS, CAL_PRESS,
CALRNGHI, FUEL_TYPE according to a set of criteria. These values are designed so
that the analog circuitry does not saturate whatever combination of conditions are
used.
CLD only; set by the current full scale range. Its values decrease by a factor of 2 from
the highest value (64) at 100 ppm to 1.
Used to set the signal level in the NDIR analyzer. This value should be set such that
the value of DET_SIG on the highest range span gas is about 7 volts. It is a feature of
the digitally programmed potentiometer used that its internal EEPROM can get
corrupted under some circumstances. If this should happen, as shown by the symptom
that the value of DET_SIG is too low no matter what the gas is, or this variable's
setting, the pot can be reset by first noting the present value of SIGNAL_GAIN, then
setting it to zero, then to 99, then to zero , and then back to its original value.
CARBON_ATOMS
See also
CAL_PRESS
CALRNGHI
FUEL_TYPEDET_SIG
RAW_SIGNAL
SOURCECURR
Direction Bidirectional
Binding
None
Type Integer
Value range
0-99
Units None
Description
NDIR only; determines the source current potentiometer setting.
Usage
Used to set the source current in the NDIR analyzer. This value should be set such
that the value of CURR_SENS is as set up originally, typically about 1A. Long bench
IRs require a higher setting, and short bench IRs require a lower setting. See
CURR_SENS for more information.
See also
CURR_SENS