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Constants
Scroll through the following list of constants until item to be altered is highlighted; press
select. Enter the new constant value when the "New Value?" prompt is displayed. Press
save change and return to the Constants Menu; press
Pressure Constants
The pressure constants are used in various combinations to configure the analyzer for output in
dew point temperature (in °C or °F) or water vapor pressure (in psia or bar). Note that dew point
temperature output is limited to -110°C. Several configuration flags from the Flags2 list in (Chapter
5) affect pressure constants and analyzer outputs as follows:
Flag 1
Flag 2
Flag 8
Flag 64
NOTE
Press_Span
For dew point or vapor pressure calculations where process pressure is known
to fluctuate, enter the multiplication factor (psia/volt) used in conjunction
with Press_Offset to convert a live voltage input from a pressure transmitter
into actual process pressure. The value is determined by the specific pressure
transmitter being used.
Press_Offset For dew point or vapor pressure calculations where process pressure is
known to fluctuate, enter the additive factor (psia) used in conjunction with
Press_Span to convert voltage input from a pressure transmitter into actual
process pressure. The value is determined by the specific pressure transmitter
being used where the transmitters minimum output is not zero.
For dew point or vapor pressure calculations where process pressure is known
to be stable, enter the known process pressure (psia) for Press_Offset and
zero for Press_Span. Note that the calculations will be based on this value. If
process pressure is changed, the value of Press_offset must be also be changed.
Other Constants
Temp_Span The multiplication factor (°C/volt) used in conjunction with Temp_Offset to
convert voltage input from cell oven thermistor into actual cell temperature.
The value is factory set and should only be changed if the thermistor is re-
placed.
Temp_Offset Enter the additive factor (°C) used in conjunction with Temp_Span to convert
voltage input from oven thermistor into actual cell temperature. The value
is factory set and should only be changed if the thermistor is replaced.
5-2 2850 Moisture Analyzer
When enabled, invokes calculations for output in dew point temperature (°C)
When enabled, invokes calculations for output in vapor pressure (psia)
When enabled, all pressure units will be in bar, rather than psia
When enabled, dew point temperature output will be in °F, rather than °C
Live pressure signal to analog input is limited to a maximum of 10Vdc.
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