Thermo Fisher Scientific Alpha pH 1000 - Manual (Page 10)

5
3.2 Back Panel
ENSURE electrical mains is disconnected before proceeding.
The back panel consists of two connectors. The first connector is the 17-way PCB edge
connector and the other is the 5-way connector.
Connection for the 17-way screw terminals (from left to right):
1. AC mains live wire 10. Alarm/Wash relay working position (NO)
2. AC mains neutral wire 11. Alarm/Wash relay common
3. AC mains protective earth wire 12. Alarm/Wash relay resting position (NC)
4. Low set relay resting position (NC) 13. Hold function switch terminal 1
5. Low set relay common 14. Hold function switch terminal 2
6. Low set relay working position (NO) 15. No connection
7. High set relay resting position (NC) 16. 4 - 20 mA for -ve connection
8. High set relay common 17. 4 - 20 mA for +ve connection
9. High set relay working position (NO)
Connections for the 5-way screw terminals:
18. Pt100/Pt1000 lead 1 terminal
19. Pt100/Pt1000 sense lead terminal
20. Pt100/Pt1000 lead 2 terminal
Note: If using a two-wire RTD, short terminal 19 to terminal 18.
Pt 100/Pt 1000 is selectable via an internal jumper. Factory default is Pt100. See Appendix
1 for directions on switching the RTD type.
21. pH/ORP (potential matching pin)
22. pH/ORP (shield)
Pt100/
0V/
PAL
pH/mV
S/
RELAY A
L N PE
100mA (F)
FUSE 250VAC
HOLD ALARM / WASH RELAYB
Pt1000
NC
- +
Important: The Alarm relay functions as an “Active Low” device i.e. it switches OFF under
Alarm condition. Therefore, the Alarm display device should be connected to the ‘NC’
contacts of the relay (11 and 12). In the Wash mode, the relay works on a positive mode.
Therefore, the Wash device should be connected to contacts 10 and 11.