Buchi B-720 - Page 6

6
BÜCHI Vacuum Controller B-720
3.2 Manual hysteresis
The tolerance range of the operating point can be selected
automatically as well as manually.
Example:
Nominal pressure 400 mbar, manual hysteresis 7 mbar.
 The pump evacuates to the desired pressure of 400 mbar,
the two-way valve closes or the vacuum pump switches
off.
 The pressure rises by 7 mbar.
 The pump evacuates again to the desired value.
3 Function
The automatic hysteresis function works by continuous (linear)
degression.
• 30 mbar for a desired value of 1000 mbar
• 1 mbar for a desired value of 2 mbar
Example:
Nominal pressure 400 mbar, automatic hysteresis 12 mbar.
 The pump evacuates to the desired value of 400 mbar,
the two-way valve in the main vacuum line closes or the
vacuum pump switches off.
 The hysteresis tolerance range for this desired value
amounts to 12 mbar.
3.3 Automatic hysteresis
Figure 5: Manual hysteresis
Figure 6: Automatic hysteresis
7 mbar
400 mbar
1
3
2
t
P
0
0
407 mbar
12 mbar
400 mbar
1
2
t
P
0
0
412 mbar