Hanna Instruments HI 9910 - Manual (Page 28)

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The controller will be dosing reductants to reduce redox to the desired
value. Since it is 25/100 = 25% away from the ideal setting, it will
keep the dosing relay acti-
vated for 25% of the time
over the predetermined 60
seconds. The terminals are
hence activated for 15 sec-
onds and off for 45 seconds
until the next cycle.
0
SECONDS mV
200 0 90
50
45 100
150
PROPORTIONAL SETTINGS
• If the setting is left at 0 pH or 0 mV, the controller will operate as
an on/off control with no proportional dosage. In this case the
controller will operate with a 0.1 pH or 7 mV hysteresis.
• Do not set the time cycle to zero
Do not set the time cycle to zero Do not set the time cycle to zero Do not set the time cycle to zero Do not set the time cycle to zero. This causes the relay to
chatter and can be detrimental to your system and pumps.
NOTE:
.g. ORP proportional control
Setpoint = 725 mV
Measured value = 700 mV
Delta = 725 - 700 = 25 mV
Proportional settings = mV set to 100 and time cycle to 60 seconds.
D mV
Seconds 15 30 45 60
25
50
75
100
15 30 45 60