2 connection diagram, Onnection, Iagram – Thermo Fisher Scientific Alpha pH 2000 User Manual
Page 18: Connection diagram, Connection for wall mounting version
3.2
Connection Diagram
Caution: Ensure electrical mains are disconnected before proceeding.
Connection for wall mounting version
RE LA RELB WASH RE LAY ALARM RELAY
-
+
Current
OP 2
29
28
19
GND +12V
-
+
Current
OP1
30
31
20
E
22
PT100/
PT1000
27
LIQ
GND
25
24
26
HOLD
14
13
12
9
10
11
8
7
N L
E
3
4
2
1
5
6
pH/ mV
1.
AC mains live wire
17.
no connection
2.
AC mains neutral wire
18.
no connection
3.
AC mains protective earth wire
19.
12V Power supply
4.
Alarm relay (NO)
20.
12V ground
5.
Alarm relay common
21.
no connection
6.
Alarm relay (NC)
22.
Earth ground
7.
Wash relay
23.
no connection
8.
Wash relay
24.
Temperature ground
9.
Relay B (SP 2)
25.
Temperature input
10.
Relay B (SP 2)
26.
Temperature sense (short to
11.
Relay A (SP 1)
terminal 25 if using 2- wire RTD)
12.
Relay A (SP 1)
27.
PMP, liquid ground in symmetrical
mode
13.
Hold function
28.
4-20 mA temperature output, -ve
terminal
14.
Hold function
29.
4-20 mA temperature output, +ve
terminal
15.
no connection
30.
4-20 mA pH output, -ve terminal
16.
no connection
31.
4-20 mA pH output, +ve terminal
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 (5 & 6).