Instruction manual

Instruction manual αlpha DO 2000

6.4 Control Relay A / Relay B (SP1/SP2) sub-function

The SP1 sub-function determines the operating parameters for Relay A; while SP2 defines the

operating parameters for Relay B. Since these groups have the same set-up parameters, they

are described together.

SETUP

HOLD

ENT

SETUP

HOLD

ENT

SETUP

HOLD

ENT

90.0

2.0

1. Select the “SP1” (Relay A) or “SP2” (Relay B) sub-function, then press the ENT key.

2. Setting set point value: press the ▲ or ▼ key to enter the value for set point 1 (set point 2)

at which your controller will activate. Press the ENT key to confirm your setting.

3. Selecting relay function: press the ▲ or ▼ key to select the desired relay function (“LO”=

low or “HI”= high). Press the ENT key to confirm your selection.

Note: Note: This parameter lets you choose the relay function. Select “LO” to

activate the relay when the dissolved oxygen value undershoots the set point;

select “HI” to activate the relay when the value overshoots the set point. SP1 and

SP2 can be selected as “Lo/Lo”, “Lo/Hi”, “Hi/Lo”, or “Hi/Hi”.

4. Setting a hysteresis value: press the ▲ or ▼ key to select the desired hysteresis (setting

range: 1 to 10% or 0.1 to 1.0 mg/l) for set point 1 (set point 2). Press the ENT key to confirm

your setting.

Note: Hysteresis prevents rapid contact switching if your value is fluctuating near

the set point. Please refer to Appendix 3 for a graphical representation of the

hysteresis.

Example: You have set your high set point at 90 % and your hysteresis value is 2 %. If your

measured value overshoots 90 %, the controller’s relay activates. The actions of the external

device will cause the solution’s dissolved oxygen percentage saturation to drop. The relay will

deactivate, when the dissolved oxygen percentage saturation value drops below 88 %.