647C 3. Functionality
25
E.g. a ratio of 5:1 (master:slave) means:
Setpoint of slave
= act. flow of master * 0.2
The master channel is determined by the index which is associated with the slave channel. The
advantages hereby are that the master remains free for declaration in other modes and more than
one master is possible. With this declaration technique, however, useless circular reference
chains, which might even be dangerous for the application, could appear. In order ro avoid this, the
software checks out each input and rejects it if necessary. Therefore, this solution offers full
advantages without risks.
Example 1: (menu extract)
CH1 CH2 CH3 CH4
MODE INDEP. SLAVE SLAVE INDEP.
INDEX 1 2
In this example channel 1 is master of channel 2, which is master of channel 3. This is an open
reference chain. The index number of a slave indicates its master channel. This declaration
technique applicated to channel 2 as master has the advantage, that this channel may be declared
as slave while being a master. Channel 4 is independent.
Example 2: (menu extract)
CH1 CH2 CH3 CH4
MODE SLAVE SLAVE SLAVE INDEP.
INDEX 3 1 2
This example shows a circular reference chain, which will never appear on 647C screen. The
software prevents its appearance by consequently rejecting wrong input. This is the reason why
some of the user’s input might be rejected.
3.7.3.3 External Mode
This mode enables external control of the MFCs through the auxiliary connector. The MFC’s
setpoint is caculated as the product of setpoint in menu EXTENDED MENU and the signal at the
auxiliary input. E.g.
Setpoint of MFC
= setpoint in EXTENDED MENU * auxiliary input / 5 V
3.7.3.4 PCS Mode
In the PRESSURE CONTROL mode (PCS) the 647C serves as the regulating unit for a pressure
controller (e.g. type 250). All gas flow channels which are configured in the PCS mode are
regulated through the pressure control signal (PCS) according to the ratio of their set points.
To Next Page
Loading...
