The 8900 Multi-Parameter Controller offers an Advanced Relay Mode that allows up to 3 relay sources to trigger 1 relay based on a combination of AND/OR logic. Any input signals connected to the 8900 can be used as relay sources.
Relay operator, source, mode, set point, hysteresis, and delay settings can be set for each of the 3 relay sources. The following is a list of the AND/OR logic operators available in the Advanced Relay Mode:
( a | b | c)
( a & b & c)
( a | ( b & c) )
( a & ( b | c) )
This tech-tip will concentrate on the first logic operated listed, ( a | b | c). Look for future tech-tips explaining the functionality of the remaining logic operators. The symbol "|" refers to OR Logic. If the condition for source "a" is true OR source "b" is true OR source "c" is true, then trigger the relay.
Consider an Industrial Wastewater Application that utilizes 3 tanks: acid tank, caustic tank, and a pH neutralization tank. One advanced relay function can be used to trigger an alarm rather than using 3 separate relays to do the same thing. See the example below:
If the level of the Acid Tank falls below 0.5 ft
OR
if
the level of the Caustic Tank falls below 0.5 ft
OR
if the level of the pH Neutralization Tank goes above 5.0 ft,
then
trigger an alarm for the technician or other automated equipment to adjust the tanks to the proper levels.
