Special Calibration - GE DewPro MMY30 User Manual

Display and Output Mode
(cont.)

Special Calibration

The Optional Display/User Interface (Option G)
5. Selecting the Analog Output Span (20 mA)
Location
in Matrix
VH The dewpoint value corresponding to the analog output
span (20 mA) is entered here. Default: +10°C.
11
Ensure the value in VH11 is always at least 20 °C above the
value assigned to 4 mA.
6. Setting the Span Value for the ppm
Location
in Matrix
VH Selection of this field sets the span value for the ppm-v
range. Default: 100.
12
Note: The offset is always 0 ppm
ppm .
v
7. Adjusting the Pressure Constant.
Location
in Matrix
VH The process pressure constant is entered in bar (abso-
lute), which is used to calculate ppm
30
unit ppm
v
total process pressure and is, therefore, independent of
the process pressure. The reason is that when com-
pressing a gas (process pressure) all partial pressures
increase by the same factor (Dalton's Law).
The gold/aluminum oxide sensor is selective to water
vapor pressure monitoring a higher vapor pressure
when the total pressure (process pressure) increases.
The formula utilized by the analyzer refers to the total
pressure of 1 bar. An elevated pressure of the process
has to be corrected by programming the actual process
pressure in bar absolute to the matrix field VH 30.
The system should be designed to maintain a constant
pressure, for instance, by using a pressure regulator in
a bypass system.
Default: 1 bar (absolute)
Description of Function
Caution!
Range
v
Description of Function
. Do not exceed 1000
v
Description of Function
is the ratio of water vapor pressure to the
November 2005
. The moisture
v
4-5