Alicat VC Series Volumetric Flow Controller - Manual (Page 15)

15
Communication Select Mode
The Communication Select mode is accessed by pressing the button below “Comm. RS-232” on the
Select Menu display. The screen will appear as shown in Figure 10.
Select
>
Unit ID
(A).....A
Baud
(19200)....19200
Data Rate......Fast
Comm.
UP DOWN RS-232
Figure 10. Communication Select Display
Unit ID – Valid unit identifiers are letters A-Z and @ (see Note below). This identifier allows the user
to assign a unique address to each device so that multiple units can be connected to a single RS-232
port on a computer. The Communication Select Mode allows you to view and/or change a unit’s unique
address. To change the unit ID address, press the “Select” button in the upper left corner of the display
until the cursor arrow is in front of the word “Unit ID”. Then, using the UP and DOWN buttons at the
bottom of the display, change the unit ID to the desired letter. Any ID change will take effect when the
Communication Select Screen is exited by pushing the MODE button.
Note: When the symbol @ is selected as the unit ID, the device will go into streaming mode when the
Communication Select Mode is exited by pushing the MODE button. See RS-232 Communications
(page 21) for information about the streaming mode.
Baud – The baud rate (bits per second) determines the rate at which data is passed back and forth
between the instrument and the computer. Both devices must send/receive at the same baud rate in
order for the devices to communicate via RS-232. The default baud rate for these devices is 19200
baud, sometimes referred to as 19.2K baud. To change the baud rate in the Communication Select
Mode, press the “Select” button in the upper left corner of the display until the cursor arrow is in front
of the word “Baud”. Then, using the UP and DOWN buttons at the bottom of the display, select the
required baud rate to match your computer or PLC. The choices are 38400, 19200, 9600, or 2400 baud.
Any baud rate change will not take effect until power to the unit is cycled.
Data Rate – Changing the Data Rate affects the rate at which the instrument dumps its data. Slow is
½ the Fast rate. The speed of the Fast rate is determined by the selected baud rate. It is sometimes
desirable to reduce the data rate if the communication speed bogs down the computer’s processor (as
is not uncommon in older laptops), or to reduce the size of data files collected in the streaming mode.
To change the data rate in the Communication Select Mode, press the “Select” button in the upper left
corner of the display until the cursor arrow is in front of the word “Data Rate”. Then, using the UP and
DOWN buttons at the bottom of the display, select either Fast or Slow. Any data rate change will be
effective immediately upon changing the value between Fast and Slow.