eutech-instruments alpha ph 190 18 din phorp controllertransmitter Manual De Usuario

- 34 - 

Appendix 4: External Relays 
 
The relays on the 

αlpha pH 190 series controller are rated for 6 amps at 110 VAC 

and can be wired directly to your final control element (provided its power 
requirements does not exceed this). However, to preserve the life of your 
controller, or if higher power is needed, it is recommended that you use the 
controller relay to drive an external relay. 
 
Diagram below shows a typical installation. Wiring should be changed 
appropriately if normally closed (N.C.) operation is desired. 
 

+ 

4 -
 20
 m
A

12

19

3

11

18

2

10

17

1

9

16

8

15

7

14

6

13

5

4

NC

NC

NC

NC

-

 4 -
 20
 mA

RE
L

A

Y

 1

 -

 N
O

RE
L

A

Y

 1

 -

  

P

O

LE

RE
L

A

Y

 1

 -

 N
C

Pt

 1

0

0

 -

 G
N

D

RE
L

A

Y

 2

 -

 N
O

Pt
 1

0

0

 -

 I

N

R

E

L

A

Y 2

 -

 PO

L

E

Pt

 1

0

0

 -

 SEN

S

E

GR

O

U

N

D

RE
L

A

Y

 2

 -

 N
C

N

LI

Q

U

ID

 G
N

D

L

pH/ORP

10

9