A float switch is a type of contact fluid level sensor that uses a float to work with a switch. Float switches are commonly used to control other devices such as alarms and pumps when the liquid level rises or falls. While there are some mechanical float switches (similar to the float in the toilet tank that cuts off the inlet water when it “fills up”), this article focuses on the electric float switch, the floats used to disconnect and reconnect ( , Disconnects and connects electrical circuits.)
Types of float switches
There are two types of float switches: base float switch and cable float switch.
Float switch switch
The float switches mounted on the stem limit the movement of the float up and down along a stem, and are performed on a floating level. Float-mounted switches can simply be a single-point switch with one float on one base, or they can be complex multi-point switches with seven floats on one base. Single-point float switches can be found in both vertical and horizontal directions.
Cable switch switch
On the other hand, cable switches are as free as the cables to which they are connected. If you do not connect the suspended float switch of the cable, it will work with current as far as the cable allows! Although cable switches are mechanically equivalent (floating and cable), they are electrically more versatile than mounted float switches. Cable switches Cable switches can be simple, with a single point that controls the switch, or more complex, with a maximum of four switch points.
Design based on reed Switch
Some surface switches based on the Reed Switch consist of several moving parts
All surface switches are designed assuming the specific gravity of water is 1. If the liquid under test has a different specific gravity, the selected vessel should not have a higher specific gravity than the liquid because it prevents the vessel from staying on the surface. In this case, the Reed Switch inside the fixed rod is not activated by the magnet inside the float.
If the liquid is high on the surface, a float of the largest possible size should be ordered to create more buoyancy and ensure the correct operation of the device.
Since the float switches are activated based on the magnetic field inside the magnet, it must be ensured that the liquid is not made of iron powder or magnetic material, as this will cause magnetic interference.
When the magnetic field of the in-vessel magnet reaches near the seed switch in the fixed rod, the status of the switch contacts changes and the electrical circuit closes. The magnetic field is blown from the reed switch. The contacts are separated from each other and the electrical circuit is opened.
How does a float switch switch work?
Almost all electric float switches work using magnets to open and close the reed switch.
How does the flute switch work?
The float switch mounted on the stem uses a floating magnet that passes through a reed switch with the function of raising or lowering the liquid, whether it is opened or closed at the switch. In a floating horizontal float switch, instead of a free float on a central stem, a reed switch is used on the hinged arm.
How does a cable switch lever work?
Cable switches have both magnets and reed switches on the float. As the float rises and falls with the liquid surface, the magnet gets closer or closer to the reed switch, causing it to open or close. In both cases, the change in liquid level is converted into a power outage signal by the movement of the magnet.
The float switch switches normally open versus normally closed
The most complex part of floating switches is to find out if a situation requires a Normally Open or Normally Closed switch. “Normally” the lowest floating position can be where the float is not floating. “Open” means an open circuit that is off. The “Closed” switch completes the circuit and turns it on. So, for each specific application, consider whether you want the liquid level to go up or down to start an operation, and whether the operation should turn the circuit on or off (think pump or alarm). Is. As the fluid level drops, a switch usually shuts off the circuit. A closed switch usually shuts off the circuit as the liquid level rises. For example, if you want your float switch to turn on a low-level alarm, you use a Normally Closed switch.
Knowing whether you need a normally open or normally closed float switch is important because most float switches with a normally open or closed function are selected at the time of purchase.
The best ways to install and set up a floating switch switch
Some floating switches are “plug and play”, and most of them are very easy to install, but it is worth taking a moment to consider the best ways to set up and install floating switches.
- First, and this applies to all float switches, make sure the float switch you purchased is the float switch you received and your float switch is compatible with the fluid you are about to place. If it’s not what you ordered, or it is not compatible, then it does not work, it does not matter that you follow the rest of these steps well.
- Second, make sure your switches are properly integrated with your control system. If you have only one switch, you only need to connect two wires. Each additional key or switch point only needs to add one wire. Do you have the right number of terminals for the number of wires coming from your switch (s)? Are your switches connected to the control system or control circuits or do they correspond directly to the controlled load? If your switch (s) are directly in line, do you have enough protection (s) against surge / voltage surges?
What are the float switches used for?
Float switches are used to detect the level. That is, float switches indicate that the fluid level is above or above (normally open), or at the bottom or bottom (normally closed) is a specific level. This is in contrast to continuous level measurement sensors, which show a continuous level reading. Depending on the specific fluid content, floating switches are a great solution if you need to set an alarm or turn the pump on or off. Do you need to know how much your home heating oil tank has reached 15%? Floating switch! Do you want to turn on the basement tank pump automatically when the water level reaches a certain point? Floating switch! Do you need to control intermittent drain pumps with low and low level alarms? Swing floating switches!
Due to the variety of materials, arrangements and capabilities of floating swing switches, a floating swing switch can be found for almost any situation. Small spaces call for small switches mounted on a pedestal, while cable switches are ideal for spaces with wider bands. Aggressive chemicals require floating switches made of stronger materials (such as plastics, instead of stainless steel).
Float switches are also useful for reducing complex automation. For some process systems, a central PLC that controls and executes everything is essential for smooth and cost-effective operation. In this case, a floating switch is just one more input, one more data point in a necessarily complex scheme. But for smaller applications – for example, one or two pumps on each of the two tanks – floating switches can be the key to success.
How to configure a float switch switch
Deciding whether your float switch to control the pump should be normally open or closed can be a bit confusing. So we want to clarify everything. When we say normally open or normally closed, we mean an electrical circuit. The open circuit is incomplete, meaning that the electric current is unable to complete the loop due to the gap. The circuit is complete without gaps and enables current to pass through the complete loop. With surface switches, these circuits are opened or closed by the float, depending on the rise or fall of the liquid level. Deciding whether you want the circuit to close or open when the float is up or down can be difficult.
The most effective way to decide is to determine what the switch should do in floating rest mode. When we say resting, we mean that the float is not suspended in the liquid. We often get it wrong with the term normal because others have misinterpreted it as a suspended float. Remember, natural in terms of key, refers to floating at rest. So, if you want the switch to turn on, or it is on when the float is at rest, then you need to close the switch normally. If you want the power to be cut off or off when the float is at rest, then the switch should be normally open. It may also be helpful to know that open switches are typically used for pumps that empty the tank, while closed switches are typically used for pumps that fill the tank.
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