Alicat P Series Pressure Gauge - Manual (Page 42)

42
TROUBLESHOOTING
Display does not come on or is weak.
Check power and ground connections and supply voltage. Please reference the
technical specifications (pages 51-67) to assure you have the proper power for
your model.
Pressure reading is approximately fixed either near zero or near full scale
regardless of actual line pressure.
Differential pressure sensor may be damaged. A common cause of this problem
is instantaneous application of high-pressure gas as from a snap acting solenoid
valve upstream of the meter. If you suspect that your pressure sensor is
damaged please discontinue use of the controller and contact Alicat.
Displayed pressure is flashing and message POV is displayed:
Our pressure gauges and controllers display an error message (POV = pressure
overrange) when a the pressure exceeds the range of the sensors in the device.
When any item flashes on the display, the pressure measurement is not accurate.
Reducing the pressure to within specified limits will return the unit to normal
operation and accuracy. If the unit does not return to normal contact Alicat.
My controller does not respond to the set-point.
Check that your set-point signal is present and supplied to the correct pin and
that the correct set-point source is selected under the SETPT SOURCE list in the
control set up display (page 23). Also check that the unit is properly grounded.
After installation, there is no pressure.
Alicat Scientific PC-Series Controllers incorporate normally closed valves and
require a set-point to operate. Check that your set-point signal is present and
supplied to the correct pin and that the correct input is selected under the
SETPT SOURCE list in the control set up display (page 24). Also check that the
unit is properly grounded.
The pressure lags below the set-point.
Be sure there is enough pressure available. If either the set-point signal line and/
or the output signal line is relatively long, it may be necessary to provide heavier
wires (especially ground wiring) to negate voltage drops due to line wire length.
An inappropriate PID tuning can also cause this symptom if the D term is too large
relative to the P term. See pages 27 and 28 for more information on PID tuning.
Controller is slow to react to a set-point change or imparts an oscillation to the flow.
An inappropriate PID tuning can cause these symptoms. Use at conditions
considerably different than those at which the device was originally set up
can necessitate a re-tuning of the PID loop. See pages 27 and 28 for more
information on PID tuning. Note: The larger the volume pressured, the longer it
takes to change the pressure in that volume.