Omega FMA 1500 - Manual (Page 21)

7.2.2 ZERO Adjustment
Shut off the flow of gas into the Mass Flow Meter. To ensure that no seepage or
leak occurs into the meter, it is good practice to temporarily disconnect the gas
source. Using the multimeter and the insulated screwdriver, adjust the ZERO
potentiometer [R29] through the access window for 0 VDC (or 4 mA respectively)
at zero flow.
7.2.3 SPAN Adjustment
Reconnect the gas source. Using the flow regulator, adjust the flow rate to 100%
of full scale flow. Check the flow rate indicated against the flow calibrator. If the
deviation is less than
+ 10% of full scale reading, correct the SPAN potentiometer
[R21] setting by using the insulated screwdriver through the access window, to
eliminate any deviation. If the deviation is larger than
+ 10% of full scale reading,
a defective condition may be present.
LIKELY REASONS FOR A MALFUNCTIONING SIGNAL MAY BE:
M Occluded or contaminated sensor tube.
M Leaking condition in the FMA 1500 transducer or the gas line and fittings.
M For gases other than nitrogen, recheck appropriate "K" factor from Gas Factor Table.
M Temperature and/or pressure correction errors.
See also section 8 TROUBLESHOOTING. If after attempting to remedy the above
conditions, a malfunction still persists, return the meter for factory service, see
section 1.1.
At this point the calibration is complete. However, it is advisable that several addi-
tional points between 0 and 100%, such as 25%, 50%, and 75% flow be checked.
If discrepancies are found, proceed to step 7.3 for Linearity Adjustment.
7.3 Linearity Adjustment
All adjustments in this section are made from the outside of the meter, there is
no need to disassemble any part of the instrument.
7.3.1 Connections and Initial Warm Up
Connect the multimeter to output pins* [2] and [3] for 0 5 VDC (or pins [5] and [15]
for optional 4-20 mA) (see Figure 2-3).
* If you are calibrating a Mass Flow Meter System that incorporates a
FMA14PD Series Command Module, the multimeter may be connected via
the DATA connector which is located at the back of the Command Module.
Power up the Mass Flow Meter for at least 30 minutes prior to commencing the
calibration procedure.
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