Edwards, nEXT Turbomolecular Pumps, nEXT240, nEXT300 and ...

B800-00-880 Issue B
Controlled venting gives the benefit of a quicker ramp down time by controlling the vent rate through a single large
orifice across the pump speed range. A full list of the venting options is given in Section 3.9
In addition there is a feature that allows a delayed start of the nEXT pump. With this feature you can close the vent
valve before you start the nEXT pump. This allows the backing pump to reduce the pressure in the vacuum system
before starting the nEXT pump.
If you do not wish to use the controller to control a TAV vent valve, you could use it to run a fan instead. You can
configure the controller so that the fan is permanently enabled.
1.4.6 Normal speed setting
Introduction
The Normal Speed is a user-selectable parameter that can be set anywhere from 50% to 100% of full rotational speed.
When the pump reaches Normal Speed, a signal is available on the Normal pin of the logic interface connector. You
can use this signal to control your application since it shows that pump speed, and therefore vacuum performance,
has reached a specific minimum level. The default setting is 80% of full rotational speed. Refer to Section 4.1.5 for
instructions on altering the Normal Speed setting.
1.5 Logic interface
The pump controller can only be operated through the logic interface. The signals on the logic interface are of three
types:
• Control inputs: these are switch-type signals that are used to control the pump
• Status outputs: these outputs identify the status of the system
• Analogue output: this provides a 0 – 10 V output for a number of pump parameters.
The logic interface has been designed to support both serial and parallel control and monitoring, operating through
one connector. For serial control either RS232(default) or RS485 can be selected using the RS485/RS232 slide switch
located on the controller (see Section 3.7).
The logic interface can be plugged directly into the Edwards TIC Turbo Controller or TIC Turbo Instrument Controller
and then use the functionality that they provide. Alternatively, the logic interface can be connected to a customers
own control system. The most useful arrangements are described in the sections below.
For more information about the logic interface, refer to Section 2.8.
1.5.1 Parallel control and monitoring
The simple parallel interface is a quick and easy way to control the pump; this is the same interface used on existing
24V Edwards Turbo Pumps. The controls that are available to use are Start and Standby. You can monitor the system
status using the Normal, Fail and Analogue output signals.
Note:
The Serial Enable switch MUST be open (no connection) and the slide switch must be in the RS232 position
(see Section 3.7).
Refer to Section 3.6 for more detailed instructions of how to use the parallel interface.
A system operating with only a parallel connection has no facility to adjust the configuration settings stored in the
controller (for example, power limit setting or controlled venting options). This would place a restriction in that all
these features would be at their factory default settings. It is possible to manually adjust the standby speed if standby
mode is selected. However, the Controller could be configured separately before fitting the nEXT pump to the
system. This is covered in more detail in Section 1.5.5.
1.5.2 Serial control and monitoring
The serial communications link provides complete control and monitoring by using just three signal lines. The Serial
data lines share the same connector pins as the parallel signals Standby and Fail. The serial data lines can be
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