Instruction Manual alpha-pH 1000
9
3.2
Back Panel
Caution: 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. 0/4 - 20 mA for -ve connection
8. High set relay common
17. 0/4 - 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)
21.
pH/ORP (shield)
0V/
Pt100/
RELAY A
L
N
PE
100mA (F)
FUSE 250VAC
HOLD
ALARM / WASH
RELAY B
Pt1000
PAL S/
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 the contacts 10 and 11.