Hanna Instruments HI 9931, Инструкция по эксплуатации

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e.g. HI 9934 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 fertilizers to reach the desired value.
Since it is 50/200 = 25% away from the
ideal setting, it will keep the dosing relay
activated for 25% of the time over the 60
second period. The terminals are hence
activated for 15 seconds and off for 45
seconds until the next cycle.
and off for 15 seconds.
In order to avoid over dosage of highly
concentrated chemicals or fertilizers, the
controller provides even a more accurate
control.
As the graphs show, it does that by
stopping the dosage as soon as the cur-
rent pulse curve intersects the dosage curve.
This means shortening the dosage period
if the chemicals have reacted quickly or
lengthening it if the measured conductiv-
ity continues to drift from the ideal setpoint
as can be seen from the graphs.
D mS
Seconds 15 30 45 60
0.20
0.40
0.60
0.80
15 30 45 60
PROPORTIONAL SETTINGS
0
SECONDS ppm
400
0
90
45 200
D mS
Seconds 15 30 45 60
0.20
0.40
0.60
0.80
15 30 45 60
D ppm
Seconds 15 30 45 60
50
100
150
200
15 30 45 60