As mentioned in previous Tech-Tips, the Advanced Relay Mode offers multiple boolean logic operators that can be used to trigger one relay based on 1, 2, or 3 relay sources. This feature Tech-Tip will provide an example of the
( a & ( b | c) ) operator.
Consider the hypothetical application below:
If the flow in a pH neutralization system exceeds 5.0000 GPM
AND
if the pH value is less than 5.0 pH or greater than 9.0 pH
then
energize the relay to add acid/base.
This setup confirms that acid/base is not added to a non-flowing line. Other automation equipment may be required to select the acid/base dosage, however, the goal of this Tech-tip is to provide an example of the advanced relay functionality.
Parameter Setup in the 8900 Multi-Parameter Controller
Relay 1 Source:
Multiple
Relay 1 Mode:
Advanced
Relay 1 Operator:
( a & ( b | c) )
a = Relay 1 Source 1, b = Relay 1 Source 2, c = Relay 1 Source 3
Relay 1 Source1:
Flow F1
Parameter setup to monitor the flow into the pH Neutralization tank.
(a)
Relay 1 Mode 1:
High
Relay 1 Setpnt1:
5.0000 GPM
Relay 1 Hys 1:
1.0000 GPM
Relay 1 Source2:
pH2
Parameter to monitor the lower pH range in the tank.
(b)
Relay 1 Mode 2:
Low
Relay 1 Setpnt2:
5.00 pH
Relay 1 Hys 2:
0.0 pH
Relay 1 Source3:
pH2
Parameter to monitor the upper pH range in the tank.
(c)
Relay 1 Mode 3:
High
Relay 1 Setpnt3:
9.0 pH
Relay 1 Hys 3:
0.0 pH
Relay 1 Delay:
0.0000 sec
The symbol "|" refers to OR logic and the "&" symbol refers to AND logic. If the condition for source "a" is true AND if the condition for source "b" OR "c" is true, then trigger the relay.
