User's Manual

D ppm

Seconds15 30 45

100

150

200

15 30 45 60

e.g. HI 9935 proportional control

Setpoint = 1600 ppm (TDS)

Measured value = 1550 ppm

Delta = 1600 - 1550 = 50 ppm

Proportional settings = ppm set to 200 and time cycle to 60 seconds

The controller will be dosing fertil-

izers to reach the desired value.

Since it is 50/200 = 25% away

from the ideal setting, it will

keep the dosing really activated

for 25% of the time over the

predetermined 60 seconds. The

terminals are hence activated for

15 seconds and off for 45 seconds until the next cycle.

0.50

DEAD BAND

OVERDOSAGE TIMEROVERDOSAGE TIMER

OVERDOSAGE TIMER

The controllers provide for an overdosage alarm system. The

operator can set the maximum amount of time that the dosage

terminals should continuously remain activated.

CONDUCTIVITY DEAD BANDCONDUCTIVITY DEAD BAND

CONDUCTIVITY DEAD BAND

(HI 9923)(HI 9923)

(HI 9923)

HI 9923 provides for a user-selectable DEAD BAND (see 15 -

Functional Diagram) which is deducted from the setpoint to decide the

intervention point when bleeding the system. The DEAD BAND can be

adjusted from 0 to 0.50 mS.

For example if 0.25 is dialed on the DEAD

BAND, with the setpoint adjusted to 4 mS/

cm (see 11 - Functional Diagram), the Con-

ductivity relay will bleed the system until the

reading reaches 3.75. It will then restart the bleed to correct the

conductivity at 4.25.

HI 9923 also provides for an ON/OFF pH control with a 0.1 pH

hysteresis.