Aalborg PWE Digital - Manual (Page 65)

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If a new calibration table is going to be created, it is recommended to start cali-
bration from 100% full scale. If only linearity adjustment is required, calibration
can be started in any intermediate portion of the gas table.
Using the flow regulator, adjust the flow rate to 100% of full scale flow. Check the
flow rate indicated against the flow calibrator. Observe the flow reading on the
PWE. If the difference between calibrator and PWE flow reading is more than 0.5%
F.S., make a correction in the sensor reading in the corresponding position of the
linearization table (see Index 83).
If the PWM flow reading is more than the calibrator reading, the number of counts
in the index 83 must be decreased. If the PWE flow reading is less than the cali-
brator reading, the number of counts in the index 83 must be increased. Once
Index 83 is adjusted with a new value, check the PWE flow rate against the cali-
brator and, if required, perform additional adjustments for Index 83.
If a simple communication terminal is used for communication with the PWE, then
“MW” (Memory Write) command from the software interface commands set may
be used to adjust sensor value in the linearization table (see section 8.3 for com-
plete software interface commands list). Memory Read “MR” command can be
used to read the current value of the index.
Assuming the PWE is configured with RS-485 interface and has address “11”, the
following example will first read the existing value of Index 83 and then write a new
adjusted value:
!11,MR,83[CR] - reads EEPROM address 83
!11,MW,83,1200[CR] - writes new sensor value (1200 counts) in to the index 83
Once 100% F.S. calibration is completed, the user can proceed with calibration for
another 9 points of the linearization table by using the same approach.
Note: Do not alter memory index 62 (must be 0.0) and 63 (must be 0
counts). These numbers represent zero flow calibration points and
should not be changed.
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Note: Once memory index 83 is changed the device firmware will
automatically update Calibration Factor (EEPROM index 61).
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Note: It is recommended to use Aalborg ® supplied calibration and
maintenance software for linearization table calibration. This software
includes an automated calibration procedure which may radically
simplify reading and writing for the EEPROM linearization table.
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