Intek RheoVac DR - Manual (Page 15)

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3.5 COMMUNICATIONS
A typical RheoVac DR instrument has an Ethernet port and two serial communications choices (RS-232
or RS-422). The ethernet port can communicate via Windows
® network Modbus or OPC. Eight 4-
20mA output signals for the probe pair are optional. Each process variable is a linear, fully temperature
and pressure compensated value on any of these readable outputs. If supplied, all 4-20 mA output
signals are scaled such that 4 mA represents 0% of the rated full scale value (except temperature, which
is 0°C) and 20 mA represents 100% of the rated full scale value (temperature is 100°C). The standard
full scale values and definitions of all process variables are listed in Table III. Communication with the
RheoVac unit using Intek supplied software is discussed in Appendix A and Appendix B of this manual.
Note: Intek recommends using the network connection for all data transmissions and RheoVac
communications.
Table III. Process Variable Definitions and 4-20 mA (optional) Range
PROCESS VARIABLE
4-20 mA
FULL
SCALE
PROCESS VARIABLE DEFINITION
ACTUAL VOLUME FLOW
ACFM [m 3 /hr]
5000
[8,500]
The actual volumetric flow rate of gases leaving the vacuum dryer. It is a
measure of exhauster capacity. Decreased capacity means pump
degradation.
TOTAL MASS FLOW
lbs/hr [kg/hr]
10000
[4,536]
The total mass flow rate of the flowing gas. Note: this value is not a
measure of air in-leak. It is a measure of total vapor and air removal and
exhauster operating capacity.
WATER VAPOR MASS FLOW
lbs/hr [kg/hr]
8000
[3,629]
The water vapor component of the flowing gas being removed from the
vacuum dryer.
RheoVac PRESSURE
"Hg [mm Hg]
30
[762]
Absolute pressure at the RheoVac DR probe head. Should be equal to or
less than turbine back pressure.
WAT ER VAPO R SPE CIFIC
VOLUME
(ft³/lb)
N/A
The inverse density of the water vapor present in the line. Not supplied as
4-20 mA output.
WATE R to AIR MASS
RAT IO
20
Ratio of water vapor flow rate to dry air flow rate. Defines “vacuum
quality.”
RELATIVE SATURATION
[%]
100
The percent concentration of water vapor in the extraction line relative to
saturation.
PARTIAL PRESSURE,
WATER
“Hg (mm Hg)
N/A
The partial pressure of water vapor in the vaccuum line. Not supplied as
4-20 mA output.
AIR MASS FLOW
lbs/hr [kg/hr]
1000
[453.6]
Actual measure of air mass flow rate passing the RheoVac DR sensor head,
normalized to standard conditions (70°F, 29.9" HgA).
RheoVac TEMPERAT URE
°F [°C]
212
[100]
4 mA = 0°C/32°F 20 mA = 100°C/212°F
Temperature of the flow media at the RheoVac DR probe head.