168-082010_ 210-212 Meter/Controller Page 15 of 17
CAUSE: Flow controller not adjusted for the dynamics of the flow system.
ACTION: Check upstream and downstream pressures. The gas supply regulator should not have excessive
lockup when flow shuts off. Also ensure that there is not a large drop in pressure between the regulator and
the instrument due to line resistance. Oscillations can also be caused if a large flow restriction is pneumatically
close to the downstream end of the flow controller. The differential pressure across the unit must be between
10-50 psig.
SYMPTOM: Little or no flow, even with Valve Override switch OPEN.
CAUSE: Plugged orifice.
ACTION: Verify the presence of a 10-50 psig pressure across the instrument. If present, shut off gas supply
and power supply. Remove orifice per Section 4.9. Examine orifice. If plugged, clean or replace as
applicable. Reassemble valve.
SYMPTOM: Flowmeter reads other than 0.00 VDC with no flow, or there is a small flow when Flowmeter
reads 0.00 VDC.
CAUSE: ZERO potentiometer is out of adjustment.
ACTION: Shut off all flow. Adjust ZERO potentiometer until output reads 0.00 VDC.
SYMPTOM: Flowmeter out of calibration and nonlinear.
CAUSE: Leaks in gas inlet or outlet fittings.
ACTION: Check all fittings for leaks by placing soap solution on all fittings between gas supply and final
destination of gas. Check Flowmeter for leaks. Replace “O” rings if required or recalibrate as necessary.
4.3. ADJUSTMENTS
4.3.1. Calibration Procedure: (Figure 4.1)
NOTE: Adjusting the SPAN pot will require the use of a calibration
reference in Step 5.
1. Connect power cable to D connector as specified in Section 2.7.
Allow instrument to warm up for 30 minutes with 10% flow and
instrument in AUTO position.
2. Set ZERO (R13) potentiometer for 0.000 VDC output.
3. Turn on gas supply to inlet of instrument. Put Valve Override
switch into CLOSE position. Adjust the orifice underneath
controller to obtain zero flow. Put Valve Override switch into
AUTO. Ensure that full range flow can still be obtained at
minimum inlet pressure.
4. Set command to 100%. Adjust SPAN (R18) pot until the flow
reference reads full scale flow (5.000 VDC). NOTE: Perform
this step only if a calibrated reference Flowmeter is available.
5. Record Flowmeter and flow reference outputs for flow rates of 20%, 40%, 60%, 80% and 100%.
4.3.2. Miscellaneous adjustments
Periodically, during normal operation, the ZERO should be checked and adjusted when required. If system
parameters change, the RESPONSE pot may require a small adjustment for optimum stability. If the
instrument is not shutting completely off when Valve Override switch is in the CLOSE position, the orifice
may require approximately 1/8 turn clockwise.
