946 Controller Instruction Manual
pg. 49
1.0 to 1.00E+6 SCCM. When MFCs with a flow rate specified in SLM are used, the SLM
value needs to be multiplied by a factor of 1000 to convert SLM to SCCM.
3. Zero
Before zeroing the MFC, ensure the gas flow through the MFC is zero. This can be done
by equalizing the pressure across the MFC.
Once zero flow rate is confirmed, set the Zero parameter to Yes. When Yes is selected,
“Ensure zero flow rate across the MFC!” will be displayed;
Press the
Enter
key to complete the MFC zero process. After
Enter
is pressed, the offset
DAC is automatically adjusted to make the display zero for the selected MFC. Also, a
U
is
displayed on the front panel under the FC indicator of the channel as shown in Figure
6-1, to indicate a user zero.
The maximum zero offset adjustment is around 3% of the full scale flow rate
of an MFC.
4. FD (Factory Default)
If YES is selected and entered for the Factory Default function, any Manual Zero is
removed and zero is restored to its factory calibration value.
After an FD command is executed, the user zeroed indicator, U, on the display will
disappear.
5. Range
This is the actual gas flow range after the Scale Factor is set. It is automatically updated
once a new Scale Factor or Nominal Range is entered.
6. OP Mode
There are five control operation modes available for an MFC connected to the 946
Controller. The following three operation modes can be executed from the Setup MFC
screen once selected and the
Enter
key is pressed to confirm.
•
Open: set the valve inside an MFC to operate at fully open condition quickly. Under
this operation mode, the flow rate can be significantly higher than the full range of the
MFC. This can be useful for system purge applications where maximum flow rate is
desired.
•
Close: set an MFC to fully closed.
•
Set point: MFC operates at the flow rate specified by the flow set point.
•
These modes can also be selected using the buttons on 946 Front Panel as
described in Section 6.7.1.
The following two operation modes are activated using the
Pressure
Control
button, but when in use,
these operation modes will be displayed in the box after OP mod.
•
Ratio: indicates that the selected MFCs are operated in either Manual Ratio Control
Mode or Auto Ratio Control Modes.
•
PID Ctrl: indicates that the selected MFC is operated under the PID Pressure Control
Mode, with the 946 Controller dynamically adjusting the flow rate of the MFC to
maintain the system pressure.