Reference Manual
748384-C
September 2003
Analyzer Variables
Rosemount Analytical Inc. A Division of Emerson Process Management
2-46
NGA2000 Reference
PTU
Direction Bidirectional
Binding
PTU
Type Enumerated
Value range
°
C;
°
F
Units None
Description
Selects the units for temperature variable display for this analyzer.
Usage
The NGA control module displays any variable with units defined as PTU, in the
temperature units selected through the variable PTU. The temperature is still
transmitted in 'C (the SI unit), but it is interpreted as 'C or as 'F as PTU is selected. It
is important to note that the value itself is not changed, it is merely displayed
differently.
See also
PPU
PVU
PURGE_IS_TOO
Direction Output
Binding
None
Type Floating
point
Value range
0-2
Units None
Description
FID only; alarm message variable
Usage
Used to show an alarm message. If the purge air pressure is too low, the value of this
variable is set to 0 causing the alarm message “PURGE_IS_TOO LOW" to appear on
the control module screen. Conversely if the pressure is too high, the value of this
variable is set to 2 causing the message "PURGE_IS_TOO HIGH” to appear on the
screen.
See also
ALARM_LVL
PVA
Direction Output
Binding
PVA
Type
Floating point
Value range
0 - 1,000,000 typically, no hard limits though.
Units ppm
Description
The primary variable - the main gas measurement from the analyzer.
Usage
PVA is the main reading from the analyzer. It is always transmitted in units of ppm. It
is generated by a complicated algorithm described in other documents. Its output
update rate may be controlled by LONPVUPDATE. It can be delayed in time in order
to align the outputs from multiple analyzers all looking, at the same sample gas, using
AMDELAYTIME. Its response time can be controlled (within the physical limits of the
measurement) by AFT90_. If the analyzer considers that its reading is invalid for
some reason, PVA is still reported but the variable VALIDITY is set to invalid. If the
analyzer is in a mode other than normal, the variable OPSTATUS will be set to some
value other than zero, but again PVA is still reported. This is true even of analyzers
that cannot perform a measurement, such as a MID with no flame.
See also
VALIDITY
OPSTATUS
PVACEMS