Level switch
The AT 120 level switch is a dry contact NO/NC float level switch, specially designed for automatic pump control in demanding industrial and wastewater applications.
Thanks to its large differential angle, it establishes a stable and smooth level contact, effectively protecting pump motors and electrical devices.
For aggressive liquids (bases, acids, solvents, hydrocarbons, etc.), the model is also available in a double-sheathed version AT 120 HR HY (High Resistance).
⚠️ Warning: due to its design, the AT 120 level switch is not recommended for slow filling rates. In this case, opt for level switches from the AQUA or SOBA range, better suited to this type of application.
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Drainage or FillingThe AT 120 level switch operates on the principle of tilt-based level detection.
The float is equipped with a three-conductor cable (COM, NO, NC), allowing the operating mode to be selected during wiring: Used in pairs with another float of the same type, it allows regulation of the minimum and maximum levels of a tank.
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In drainage mode, the level switch triggers pump startup in the high position (overflow protection). An electric current flows through the float to the connected device (control relay, pumps, valves, alarms).
Once the tank is empty, the level switch cuts the electrical circuit to protect the equipment (pumps) in the absence of water in the tank.
In filling mode, the electrical circuit inside the switch closes (NC) when the switch is in the low position. Thus, the pump starts to fill the tank.
Ballast positioningThe triggering of the float level switch (switching angle) can vary depending on liquid agitation, filling/drainage flow rate, but especially depending on the ballast positioning or fixing point. Indeed, the cable length between the counterweight and the float switch determines the amount of liquid that rises or falls to bring the float switch to change state. You have the possibility to adjust the counterweight on the device cable to optimize its operation. |
You have the possibility to adjust the counterweight on the device cable, so the greater the distance between the ballast and the float, the greater the level difference will be, consequently the switching angle will be larger.
This allows the float to adapt to possible turbulence in the liquid but also allows the float to work in a wide range of densities.
Below are indicative values for the BIP STOP with minimum and maximum cable length to ensure correct operation:
Min. value Y = 10cm > X ≈ 30-35 CM
Max. value Y = 30cm > X ≈ 60-65 CM
To adjust the ballast on the cable, simply pull on the plastic or resin ballast to unclip it from the clamping ring or O-ring. Then slide the clamping ring/O-ring to the desired location and replace the ballast on it, so that the weight is locked on the cable.
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Float fixingThe float level switch can be suspended via the cable sheath, using the FIXCAB fixing accessory, which allows proper fixing of the electrical cable at the desired height and allows precise adjustment at any time. Be careful when using clamps or other elements during fixing that can damage the cable and deteriorate the device by allowing water to enter inside the float level switch by capillarity.
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Electrical connectionIn outdoor or humid spaces, the electrical connection of the float level switch must be watertight and properly insulated in a hermetic box, thus preventing water or other contaminants from entering the cable. This helps prevent water infiltration that could compromise the safety of electrical connections as well as the lifespan of the float. The electrical connection box should never be placed inside the tank. The cable and its capillary can be extended using a standard signal cable. We equip our floats with the cable length you want to avoid connections that would harm their operation.
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Unlike flat sensors, the AT 120 offers omnidirectional detection. Its shape allows it to react to water movements regardless of its position in the liquid.
This guarantees more reliable detection, especially in agitated environments or subject to turbulence.
Cable fixing accessory (FIXCAB) strongly recommended for all suspended floats.
Multifunction socket ideal for pump control.
Adjustable ballasts are essential for proper float operation.
Level control relay with alarm.
To best define the float level switch suited to your needs, ATMI offers a wide range of level switches for liquids and solids in various applications.
