Hanna Instruments HI 9914 User Manual

Page 11

If the

CONT/PAUSE switch of the Circulation pump is in

CONT position, the circulation pump will act as described
above.
If the

CONT/PAUSE switch of the Circulation pump is in

PAUSE position, the circulation pump will not run the step 5.

When the low-level sensor is not used, the low-level condition is not sensed
by the controller. The user must take care to stop the user input com-
mand before the water in the tank goes below the low level.

When the high (alarm) level sensor is not used and
the normal level sensor does not work properly, the
controller is unable to detect when the water reaches
the high (alarm) level. In order to stop the control-
ler, the humidity sensor must be placed where it can
sense if the water pours down from the tank.
If the tank assembly is minimal, the irrigation takes place without using
the user input command. Only the normal level and humidity sensors are
used. The controller fills the tank at normal level and begins the Conduc-
tivity & pH correction. The user can add water at any time or wait until
a good water composition is signaled.

Step 4:
The water nozzle is closed, circulation pump is running and the Conduc-
tivity & pH controls are activated. The Conductivity control has the
priority over the pH control.
• If the timer feature is activated, the control is on for a selected period

(1-10 minutes) and off for the remaining period until 15 minutes.

• If both the conductivity and pH values are good for at least 30

seconds, the controller goes to step 5.

• If the normal level sensor remains open for about 15 minutes, the

controller goes back to step 3.

Step 5:
The Conductivity & pH values are good. The Circulation pump is running
and the controller waits for user input. This state is signaled on the front
panel by

FEED OK LED and externally through a 15mA current between

the

FEED OK and INPUT COMMON pins.

• If the water composition is not good, the controller goes back to step 4.
• If the normal level sensor remains open for about 15 minutes, the

controller goes back to step 3.

• If the FILL button (or the external fill button connected between

FILL

and

INPUT COMMON) is pressed while the NORMAL LEVEL sensor is

open, then the controller goes back to step 3.

• If the user input command is active (the contact is closed between the

USER INPUT and INPUT COMMON pins), the controller goes to step 6.

Step 6:
The Feeding pump is activated. The control of Conductivity and pH is
inhibited.
• If the user input becomes inactive (the contact between the

USER

INPUT and INPUT COMMON pins is open), the controller goes back
to step 3.

• If the low level is reached (the low-level sensor contact is open), the

controller goes back to step 3.

• If the water remains under normal level for about 15 minutes (the

normal level contact is open), the controller goes back to step 3.

The tank can also be filled by pressing the

FILL button on the front panel

(or the external fill button connected between

FILL and INPUT COMMON

pins) when the irrigation is completed.