26
7.3
Analog output Calibration of XFM Mass Flow Meters
XFM series Mass Flow Meters are equipped with cali-
brated 0-5 Vdc and 4-20 mA output signals. The set of
the jumpers (J7A, J7B, J7C) on the printed circuit board
is used to switch between 0-5 Vdc and 4-20 mA output
signals (see
Figure c-1
“XFM configuration jumpers).
Figure c-1
XFM Analog Output Configuration Jumpers
The XFM analog output calibration involves calculation
and storing of the offset and span variables in the EEP-
ROM for each available output. The 0-5 Vdc output has
only scale variable and 20 mA output has offset and
scale variables. The following is a list of the Gas inde-
pendent variables used for analog output computation:
Index Name
Description
25 AoutScaleV
- DAC 0-5 Vdc Analog Output Scale
27 AoutScale_mA - DAC 4-20mA Analog Output Scale
28 AoutOffset_mA - DAC 4-20mA Analog Output Offset
Note:
The analog output available on the XFM Digital Mass Flow Meter
was calibrated at the factory for the specified gas and full scale flow
range (see the device’s front label). There is no need to perform analog
output calibration unless the EEPROM IC was replaced or offset/span
adjustment is needed. Any alteration of the analog output scaling
variables in the Gas independent table will VOID calibration warranty
supplied with instrument.
,
FUNCTION
J7A
J7B
J7C
JCD
ANALOG
0-5 VDC
5-9
6-10
7-11
OUTPUT
4-20 mA
1-5
2-6
3-7
RS485
TERMINAL
RESISTOR
OFF
8-12
ON
4-8
AutoZero/Reset
push button.
J7 Jumpers
9
10
11
12
5
6
7
8
1
2
3
4
A
B
CD
Note:
It is recommended to use the Aalborg® supplied calibration and
maintenance software for analog output calibration. This software
includes an automated calibration procedure which may radically
simplify calculation of the offsets and spans variables and, the reading
and writing for the EEPROM table.
,
