justed. Once the target value setting is reached, the RV 10.4002 vacuum valve interrupts the suction line (included in scope of supply). If additional

switching on and off of the vacuum pump is desired, please use the RV 10.4003 pump control (accessory).

The device will fall slightly short of the target value setting due to the time difference in the millisecond range with the vacuum value, the target value

comparison and the switching of the vacuum valve. Natural leakage from the apparatus now causes another increase in the pressure value of the

system, which in turn is detected by the integrated pressure sensor.

If the target value is exceeded, the vacuum valve is reopened and the vacuum pump in operation lowers the pressure. The pressure curve shown on

the display fluctuates around the set target value.

The pressure difference between activating/deactivating the valve can be set using the vacuum hysteresis value (see Vacuum Settings). The value is set

to 10 mbar as standard.

The quality of the control depends on the suction power of the pump (rotation speed), the tightness of the system and signal delay time of the elec-

tronics used.

Automatic boiling point recognition is not possible when using two-position control.

Schematic view of a two-position vacuum control

Speed-vacuum control

Imprecision of the two-position control is avoided by using the speed-vacuum control.

However a vacuum pump with a controlled speed is needed for speed-vacuum control; the RV10.4002 vacuum valve is not required and must not

be connected!

To do so, connect the vacuum pump (e.g. KNF N920 speed controlled pump) to the port on the rear of the rotary evaporator.

With this kind of control, the speed of the pump, and therefore its suction power, is reduced the closer the measured pressure reaches the target value.

Once the target value is reached, the pump only operates according to the leakage rate.

It is possible to achieve quieter operation and more exact vacuum control.

The speed-vacuum control on the RV 10 is controlled automatically as soon as an appropriate vacuum pump is attached.

Automatic boiling point recognition is possible with this type of control, i.e. the system reaches and keeps the solvent at its boiling point in automatic

mode.

As it is not necessary to know the boiling point of the solvent when in automatic boiling point recognition mode (unlike in the case of volume-depen-

dent distillation), these two operating modes are mutually exclusive.

Schematic view of speed-vacuum control