Float switches work much like a standard light switch, they open and close contacts to control whether or not signal current can pass through. They are either Normally Closed, meaning current is flowing, or Normally Open, meaning current is not flowing. The “Normal” state is when the float switch is down, resting on it’s cable or float stop.
In other words, float switches consider an empty state normal (no liquid to lift the float). A Normally Closed float switch in an empty tank would have current flowing through it, activating whatever process it is supposed to - such as turning on a pump, or sounding an alarm. A Normally Open float switch, on the other hand, would break the current in an empty tank, and would not close, or activate, until the tank was full enough to lift the float.
Float switches are pretty straight forward, without many bells or whistles. However, there are several reasons why ours stand out. Most impressively, the Kari cable suspended float switches can have a single switch point, or up to four, all in one float. This is unheard of amongst competitor float switches. These floats are set up for various different applications, like fill control or empty control with an isolated alarm.
Our stem mounted float switches can have up to seven floats - each with one switch. These are custom placed according to your application needs. They can operate in temperatures up to 212° F (100° C). Unlike cable suspended float switches, these don’t need a wide area to operate. They’ll work anywhere large enough to fit the sensor.
Our miniature float switches are a versatile group, some capable of operating in temperatures up to 392° F (200° C). They are very compact, perfect for small tanks.
Point level sensors in general are great for controlling pumps and alarms when a liquid level must be maintained within a certain window of acceptance. A great example is pump control. If tanks get too full, there are two risks: overflow, and if filled from the bottom, pump failure. If a tank gets too low, you risk pump failure as well. Float switches are a great method for turning pumps on and off.
Some float switches need a controller to add logic to this on/off equation. If a pump is controlled directly by a switch with no logic, and the liquid level has stopped right at the float (like it’s designed to do), any ripple at the surface will cause the float to bounce up and down, chattering between on and off. This would burn a motor out quickly.
The control adds hysteresis, which tells the pump not to chatter, but to turn off at one level, and turn on only at another level. If you’re filling a tank, for example, the top float would tell the pump to turn off. The pump would stay off until the tank had emptied to the level of the bottom float, where it would turn on - staying on until it reached the high level once again.
Some float switches, like our Kari line, have hysteresis built in. The floats have multiple (up to four) switch points in a single float. They’re designed with a mechanical hysteresis for different applications, such as tank fill or empty, which controls which switch point is for on and which is for off. Some switch points are designed to handle alarm configurations as well.
Finally, many float switches are used simply for level indication. Some applications call for a series of lights that indicate something like 25, 50, 75, and 100 percent full. It’s not continuous level measurement, but it’s close.
Yes. Our FT-100 series is a simple cable suspended float switch with one switch point. Our MLS model is a tank mounted switch on a rod and can be easily adjusted to get the right level. Finally, our LF models are miniature switches that are tank mounted as well. They're meant to be installed right at the switching level.back to top
Yes. Most float switches are, by definition, a simple apparatus. You can install a simple apparatus in a hazardous location as long as you're wiring intrinsically safe. In other words, the float switch has to be wired to an appropriate safety barrier or isolator.
For our more complex FL series, we have a Class 1, Div 1 certification on our FLX model.back to top
Simple, buy a Kari float switch. It has up to 4 switches in a single float. So you can have a high and low switch point with a high and low alarm, or you can have 4 individual switching levels in a single float.
You can also get a Kari model with 1, 2, and 3 switches in them. They come in 19 different configurations - including built-in hysteresis - for multiple pump control and alarming applications.back to top
That depends on your definition of high temperature. Some of our miniature models can operate in temperatures up to 390° F. Our FL series maxes out at 212° F. Our cable suspended models can only do 140° F.back to top
Yes, on a few of them. Certain of our miniature line (LF series) allow you to flip the float to change the NO/NC state.back to top
Yes. The float can be moved up and down the rod to adjust the switch point. Simply move the float stops. You can also cut the rod to size.back to top
Yes, until you reach the limitations of the mounting threads. Cable suspended float switches do not come with mounting threads. They're intended for non-pressurized environments.back to top