Safety and Control Systems

Monitoring your Fish Farming

The intensification of fish farms results in higher stocking densities. The new systems that have been developed make this possible. Where life support systems such as aerators are necessary, problems result from power cuts or other accidental interruptions.


Aqua – Control Compact

Aqua-Control – Monitoring and control system … for more security in your fish breeding
… life insurance for your fish
The complete Aqua Control system allows comprehensive monitoring and control of fish farms, with full software visualisation. Functional customisation is possible, with the addition of the feeding programme, or the diary of the complex, for example. The basic concept of this compact system is to deliver fully pre-wired units with minimal installation work.

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Aqua – Control Compact

We can now offer our proven control and monitoring system, AQUA-CONTROL, for use in transporting live fish by truck. With this system, you can see at a glance what the oxygen level is in each tank. The truck driver has a full picture in the cab. Frequent stops for the inspection of the fish in the tanks (for burning of the gills, for example) are a thing of the past. Transport your fish safely and without losses. Because of our monitoring system, use of oxygen can be minimised during transport, reducing costs.

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Handy Instruments

Portable instrument for measuring dissolved oxygen. Works with a new probe and microprocessor controlled electronics.

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Aqua-Control One

New, compact, fixed oxygen monitoring and control system. The Linn company has manufactured effective oxygen monitoring and control systems with 4 or more probes for many years.

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Stationary Oxygen Probe

A key component of any monitoring system is an oxygen sensor installed directly in the pond.

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  • Aqua – Control Compact

    We have developed a further extension to our Aqua-Control system for quick and easy use in fish farms. The basic concept for this compact system is to supply a complete pre-wired unit that can be brought into operation in fish farms with little installation and wiring effort.

    The plastic switch box is completely pre-assembled and wired. A PLC display module is visible which constantly displays the actual values of the connected oxygen probes. The integrated keypad can be used to set the desired target values of the input systems and, in addition, an alarm threshold. Furthermore, the switch box contains a Residual Current Device (RCD), the necessary motor protection switches for the connected devices as well as the control relay for the sockets of the input systems and the solenoid valves of the oxygen supply line.

    Motor protection and RCDs of the devices are constantly monitored (in addition to the oxygen value) and, in the event of irregularities, forwarded to an alarm switching device via a potential-free contact. The connection of further signal transmitters (such as float switches, level monitors or temperature probes) can be achieved easily. Five sockets are located on the lower half of the switch box: four controlled sockets for plugging in the input systems and another for flexible use. Also included are four sockets for connecting the oxygen probes.

    Aqua Control compact is designed for rapid application. Only the power supply line, the oxygen supply line and a control line (if the system is to be connected to an alarm centre or a PC) are to be connected on site. All other wiring is already in place. All you need to do is plug in your input systems and the oxygen probes!

    The most convenient solution is to combine Aqua-Control Compact with a computer. By means of a 2-wire USB line, the PC enables a central setting of all pre-sets and alarm values. The actual values can be displayed in your personal pond view. It is also possible to record the O2 saturations over any length of time.

  • Handy Instruments

    Handy Polaris
    Portable instrument for measuring dissolved oxygen. Works with a probe with membrane and electrolyte (Clark Sensor) and microprocessor controlled electronics. Handy Polaris has a large display, you can choose which parameter should be shown in large figures. Handy Polaris has also automatic calibration, an automatic probe check and a choice of language! It is the easiest Handy to use, and is supplied with a carrying wallet, maintenance kit and instructions.

    Handy Polaris 2 is designed as an advanced solution for dissolved oxygen and temperature measurements with data logging. Based on Polaris functionality, Polaris 2 includes a datalogger with up to 99 memory blocks and 3000 memory cells and data can be transferred to a PC using a USB link which is purchased separately.

    Handy HI 9147
    The Handy HI 9147 is made by the Hanna company, and is an inexpensive oxygen meter. The instrument has a waterproof casing and a galvanic oxygen probe (complete with 4 m cable). The oxygen measurements are expressed as percentage saturation or mg/l. This instrument also measures temperature and has automatic temperature compensation. The display can also be illuminated, for use in low light conditions. The HI 9147 comes complete with replacement membranes, O-rings, electrolyte and a transport case.

    pH checker
    This pocket instrument makes measuring pH easy! It is calibrated automatically with standard buffers, and is then ready for use. No calibration fluid is necessary. The pH-value (0-14) is indicated, and is readable to one decimal place.

    In addition to the pH-value, temperature is also measured (automatic temperature compensation) and indicated simultaneously on the display. The device is waterproof and only weighs 85 g. An inexpensive spare electrode can be supplied, and is easy to replace. This pH checker offers the capability for fish farmers and hobbyists to determine the pH-value of their ponds quickly and reliably.

  • Aqua-Control One

    The Linn company has manufactured effective oxygen monitoring and control systems with 4 or more probes for many years. During this time, our customers have often asked us to produce a reliable, but cheap device to measure dissolved oxygen in a single pond. This new system, the Aqua Control One, is the answer!

    It is delivered complete and ready for use. At the heart of the system is the control unit, which is enclosed in a splash-proof enclosure. This can easily be hung in the desired position. All that is necessary is to connect to the power supply (230 V 1 ph or 400 V 3 ph), and suspend the oxygen probe in the pond or water to be monitored. The display will show the current dissolved oxygen level, in percentage saturation, continuously. Aqua-Control One is now available with two different oxygen probes. In addition to the already well-known probe (Clark sensor with membrane and electrolyte), a version with optical oxygen probe is now available.

    Linn´s Aqua Control One offers an inexpensive, ready-to-use, durable solution for the monitoring of dissolved oxygen and control of equipment in ponds. Also suitable and affordable for Hobby – and koi pond owners, with the reassurance that it has been field- tested by expert fish farmers. Aqua Control One is compact and portable and therefore flexible. It can be moved around to where it is most needed at the time, if it is not possible to monitor every pond.

    LINN Aqua-Control has developed to provide the complete monitoring/control/regulation of your fish farm – combined with complete software for all necessary data and readouts. The software is individually created by us for your farm from a variety of modules (e.g. module pond book or manual feeding). All changes in your farm are automatically recorded or can be easily and simply implemented with a mouse click! The heart of the system is a programmable logic controller (PLC) from the industrial sector. The combination of different inputs from a modular system makes it possible to achieve almost any desired function. Each system is a bespoke solution created according to specific customer requirements.

  • Stationary Oxygen Probe

    A key component of any monitoring system is an oxygen sensor installed directly in the pond. This sensor/probe optimally protects against any malfunctions (electrical outages, motor malfunctions etc) that could lead to a reduction in oxygen levels. We are generally able to combine our monitoring and control systems with a range of different probes. All probes work with a 4 – 20 mA current. Probes measures oxygen in % saturation (mg/l on request).

    DRYDEN Probe
    This probe is also an electro-chemical sensor. In this type, the transducer is located outside the sensor itself. The electronics are not in the sensor casing and therefore not constantly under water. The transducer can be kept in the control box as a rail module. Again, a two-lead cable is sufficient.

    OXYGUARD Probe
    This type of probe is an electro-chemical sensor (with membrane and electrolytes). This technique has proven itself in daily use in fisheries. In the Oxyguard probe, the necessary electronics (transducer) are located within the sensor. This is advantageous, as an additional control box for the transducer is not necessary. The sensor can be calibrated using a potentiometer directly on the sensor. A two-lead cable is sufficient to power the sensor.


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