Hanna Instruments HI 8711 - Manual (Page 27)

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When acid dosage is active, the ACID LED lights
up, while during alkaline dosage, the ALK. LED
turns on (HI 8710 only).
When oxidant dosage is active, the OXID LED
lights up, while during reductant dosage, the
RED. LED turns on (HI 8720 only).
When the dosage switch is in OFF or continuous
ON position the corresponding LED blinks (the
LED on the right side of the switch).
If the dosing switch is in OFF position the dosing
and alarm relays are deactivated and the ALK.
or ACID LEDs are OFF.
If the dosing switch is in ON position the DOSING relay is always
activated and the ALK. or ACID LEDs blink; the ALARM relay is activated
and the ALARM LED blinks according with the input reading, setpoint
and ALARM threshold.
If the dosing switch is in AUTO position, all relays are controlled
depending on measure, setpoint and ALARM threshold.
If overtime dosing function is enabled overtime
OFF terminals (1,2) open and the DOSAGE switch
is in AUTO or ON position, an ALARM is generated
if the dosing time exceeds the overtime set period
(overtime knob on the rear panel).
The dosing relay is not deactivated if the DOSAGE
switch is in ON position but is deactivated if the
switch is in AUTO position, when the overtime
period is overpassed.
To leave overtime ALARM mode and return to normal operation move
the DOSAGE switch in OFF and then in AUTO or ON position again. The
dosage and alarm relays will be controlled depending on the measure,
setpoint and alarm thresholds. The overtime counter is reinitialized to 0.
The actual pH or ORP value of the test solution is displayed.