CiDRA GVF-100 Gas Volume Fraction Monitoring System - Manual (Page 77)

Copyright © 2006 CiDRA Corporation Page 10-3
20639-01 Rev 03
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Altitude
Used to calculate the atmospheric pressure corrected for elevation.
Enter the elevation above or below sea level.
The following equation is used within the transmitter to correct for
elevation.
P
atm
= 14.696 * [1 – ((Alt * 10 -3 )/145.45)] 5.2561
where: P
atm
= absolute atmospheric pressure corrected for altitude (psi)
Alt = altitude (feet)
Note: If an “absolute” scaled pressure transducer is used it is not
necessary to enter altitude.
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Set Date/Time
The date and time is entered in the transmitter in order to set the time
stamp that will be applied to data downloaded on the USB Port
(discussed later in this manual). Whenever possible, the time and
date should to be synchronized to the process control system. Note:
The time is not automatically updated to reflect daylight savings time.
10.1.2 Output Config Menu
These inputs are used to configure the various outputs from the
transmitter.
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4-20mA (CH 1 & CH 2)
Several selections are available for outputting under the ‘4-20mA’
setup menu screens.
The ‘Output Sel’ sub-menu selection permits selection of the
parameter to output on the 4-20mA channels. The GVF meter permits
selection of the ‘GVF’, ‘SOS’ or ‘Blank’ for no display as the output
parameter.
The ‘Power Sel’ selection is used to specify whether ‘Internal’ power
or ‘External’ power is used to drive the 4-20mA current output.
The ‘Low End’ and ‘High End’ menu selections allow the user to
change the upper and lower values that are output on the 4-20mA
channel based on 5,000 ft/sec as the maximum output value.
The following figure gives an example screen shot of a user specified
‘Low End’ setting for 4-20mA CH1. The user settable percentage is
located on the left side of the bottom line of the display, with the
corresponding sound speed value shown on the right. The
percentage represents a point within the output range of the meter.
This is represented by 0%=0 ft/s and 100%=5000 ft/s. As the
percentage is changed between 0 -100%, the corresponding sound
speed value is indicated.