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

B800-00-880 Issue B
Figure 12 - Controller status information
Installation
1. Standby speed increase button
2. RS485/RS232 Switch
3. Controller connector socket
4. Standby speed reduce button
5. Alarm LED
6. Status LED
7. Normal LED
CAUTION
When connecting the nEXT pump to a PC, remember that the 0 V pin on the RS232 connector may well be
connected to earth through the PC. If this is the case ensure that the 0 V rail of the 24 - 48 V supply is not also
connected to earth at some other point such as at the power supply. If you do not wish to have the 0 V rail of
the 24 - 48 V supply connected to earth at the PC an opto-isolated interface to the PC should be used.
The nEXT pump can connect directly to the RS485 or RS232 serial input on your control equipment or a PC as shown
in Figure 13 and 14. In this configuration the PC is the serial link master and the nEXT pump is the slave. The distance
over which the serial link will work is dependent on any difference in voltage between the 0 V at the sending and
receiving end. If the 0 V reference at the receiving end is within 0.3 V of the 0 V Control Reference pin on the nEXT
pump control connector then the serial link should be capable of operating at distances up to 6 m. An interface circuit
external to the nEXT pump may be required for longer distances.
The software in the nEXT pump is capable of operating with several pumps connected to a single serial link master.
This is referred to as multi-drop mode. The RS485 option is recommended for multidrop mode. With the RS232 option
© Edwards Limited 2009. All rights reserved. Page 33
Edwards and the Edwards logo are trademarks of Edwards Limited.