อุปกรณ์วัด Control System (Fertigation Control System panel mount, fertilization control by volume, EC monitored)
Fertigation Control System panel mount, fertilization control by volume, EC monitored
The HI 8021 fertigation controller provides up to 10 irrigation programs to irrigate up to 16 sectors using time or volume control. Each irrigation program has one pH and one EC setpoint. The start condition of the program, the irrigation sectors and the time or volume for each sector are user defined. The irrigation water is pH corrected based on the pH control, with acid or alkaline solution and can contain nutrients for crops based on up to 4 fertilizer receipts. Fertilizer dosing is performed based on the volumetric control. Additionally, an EC level monitoring/alarm is implemented to stop irrigation should the conductivity exceed the maximum set level in order to avoid damages to irrigated crops. Agitator control and filter cleaning control is performed automatically. The instrument reads up to two EC probes redundant in-line for safety to measure the current irrigation water EC. The two pH electrodes are mounted in-line redundant for safety to read the irrigation water pH. The instrument provides an alarm system and logging organized on three user selectable levels.
Irrigation control differs based on the type of control: by irrigation water volume or by irrigation time; the number of sectors that have to be irrigated, the available sources of water for irrigation – one or more with or without reusing the irrigation drain water.
Irrigation control is started by opening the irrigation valves and starting the main irrigation pump. The control of all these elements is performed by the controller based on concepts of irrigation programs.
Up to 10 irrigation programs can be set by the user with different irrigation parameters: irrigation periods, type of irrigation control, irrigated sectors and volume or irrigation time specified for each sector, conditions to start irrigation such as time, accumulated solar radiation, low level in tanks (hydroponic crops), temperature variations, linked to another program, priority of program, number of repetitions. For irrigation water, each program has a defined pH set point, EC set point (if the quantity of fertilizer is dosed according with conductivity), and receipt of fertilizers. Control of agitators is specified by programs according with the irrigation periods.
The quality of irrigation water is assured by proper control of pH and the quantity of nutrients (fertilizers) present in irrigation water.
Fertilizer can be dosed during irrigation using the Venturi tubes principal or with motorized valves. The control of the quantity of dosed fertilizer can be performed using the volume counters.
The system supports dosing from up to 4 fertilizer tanks with specific receipts.
The concentration of the fertilizer in irrigation water can be controlled based on the conductivity reading, proportional with irrigation water based on the receipt or ratiometric, in which case the certain quantity of fertilizers are added with the amount of programmed water.
The pH control is performed in order to adjust the pH of water to the irrigation program set point.
The pH correction can be performed with alkaline or acid solution based on the characteristic of the incoming water.
The control of pH and EC is performed with PID, PI or proportional control. The tuning of the PID control can be accomplished by the user manually, or automatically by the PID auto-tuning feature.
Agitators and filter cleaning
The automatic control of agitators used in fertilizers tanks and filter cleaning system complete the needs of a standard fertigation system.
In order to keep the fertilizer concentration constant before and during the irrigation program, the fertilizers are mixed in their tanks based on the agitators program. The system can manage up to two filters mounted to protect the probes and in-line dosing elements.
With differential presostates, the filters are monitored and when necessary, the irrigation programs are automatically suspended and washer filter cleaning is started. This process removes any deposits and sediments that may appear on filters to increase the systems life.
Redundancy of EC and pH probes
For safety reasons, the systems can be equipped with 2 conductivity probes and two pH electrodes in redundancy so that the system can generate an alarm in the case of reading differences between them. A third conductivity probe can be mounted to verify and compensate the incoming water conductivity.
The logging of the controller can be selected on three levels: input reading variations, statistics of reading (average of pH and EC) or events (start of programs, opening valves, …).
The alarms of these systems are related to measured water quality parameters like conductivity and pH: out of range, differential reading between redundant probes; over dosing of conductivity or acid or alkaline correction solution, tanks at low level or no dosing detected by counter movement. Similar alarms can be generated after the units self-diagnostic tests are run.
All the sensors: EC, pH, temperature are connected to the controller via transmitters.
pH and EC are temperature compensated on the transmitter level. The output of analog transmitters can be calibrated at two points for pH and conductivity. Also, the controller offers a calibration in two points for pH and one point for conductivity.
User interface and digital connection
The user interface is based on an 4 x 20 character line LCD, organized for settings and consultancy. The UI has multi-language support.
The RS232 connection permits the connection to a PC (dedicated PC software HI 800104).
Internal back-up system
The systems internal back-up power system offers a special feature; in the case of losing external power, the controller will stop the irrigations and memorize the irrigation programs that were not performed. The controller will start from the uncompleted programs after power has been restored. The programs will be executed based on their priority level with full respect of the quantity of irrigation water, pH level, and concentration of fertilizers.
Additional features that can be found are control of the external power supply and control of mixing of different water sources (clean water, drain irrigation water).
Irrigation Control Time/volume control, 10 programs/5 priority levels with up to 99 repetition
Irrigation Start Condition by Time, by solar radiation, by 5 external tank low level
Fertilization Control by volume, the EC monitored
Fertilizers up to 4 motorized valves
pH Control/Correction acid or alkaline
Agitators Control yes
Filter Control/Cleaning 2 differential presostate/2 filter cleaning relays
Fertilizer Tank Levels/Counters Control counters
Irrigation Counter yes
Acid/Alkaline Tank Level/Counter Control counter
EC Inputs Up to 2, 0.0 to 10 mS/cm
pH Inputs Up to 2, 0.0 to 14.0 pH
Compensation EC, pH
Solar Radiation Input 1; 0 to 2000 W/m2
Wind Speed no
Engine Power Back-up no
Irrigated Sectors up to 16
Mixing Source of Water no
PC Connectivity RS232
Alarms yes, user selectable levels
Logging yes, three levels
Power Supply 115V/220V ±10% 50Hz/60Hz
Dimensions 178 x 260 x 116 mm (7.1 x 10.4 x 4.6”)
Weight 3.4 Kg (7.5 lb.)
HI 1001 Flow-thru Monitoring pH Electrode with BNC Connection and 3 m Cable
HI 7004L 4.01 pH Buffer Solution
1 x 500 mL bottle
HI 7039L 5000 µS/cm EC Solution, 500 mL Bottle
HI 7007L 7.01 pH Buffer Solution
1 x 500 mL bottle
HI 70300L Electrode Storage Solution
1 x 500 mL bottle
HI 7061L General Purpose Cleaning Solution
1 x 500 mL bottle
HI 710005 Power Adapter, 115 Vac to 12 VDC, US Plug
HI 710006 Power Adapter, 230 Vac to 12 VDC, European Plug
HI 60542 Electrode Holder for In-line Direct Pipe Installation, PG 13.5 Thread
HI 98143-22 pH and EC Transmitter with Galvanic Isolated Output
designed to be used with the HI 8000 series
HI 3001 Flow-thru Conductivity Probe with 3 m cable