That’s right! APG’s products are proudly produced in the USA at the company’s facility in Logan, UT. With very few exceptions, APG’s products are manufactured from start to finish in this facility. The following is a list of sensors that are manufactured from start to finish at the facility in Logan:
- Ultrasonic Level Sensors
- Magnetostrictive Level Transmitters
- Resistive Level Transmitters
- Submersible Pressure Transducers
- Pressure Transducers
- Hammer Union Pressure Transducers
- Digital Pressure Gauges
- Multi-Point Level Switches
- Stainless Steel Float Switches
THE BASICS OF FLOAT SWITCHES
What is a Float Switch?
A float switch is a type of contact liquid level sensor that uses a float to operate a switch. Float switches are commonly used to control other devices such as alarms and pumps when a liquid level rises or falls to a specific point. While there are some mechanical float switches (similar to the float in a toilet tank that turns off the incoming water when the tank is “full”), this article will focus on electrical float switches, floats that are used to open and close (i.e., turn off and on) electrical circuits.
Types of Float Switches
There are two types of float switches: stem-mounted float switches and cable-suspended float switches.
Stem-mounted Float Switches
Stem-mounted float switches constrain the movement of the float to up-and-down along a stem, and operate on a one-float-one-level basis. Stem-mounted float switches can be as simple as a single-point switch with a single float on one stem or they can be complex multi-point switches with as many as seven floats on a single stem. Single-point float switches can be found in both vertical and horizontal orientations.
Cable-suspended Float Switches
Cable-suspended float switches, on the other hand, are as free as the cables they are attached to. If you don’t tether a cable-suspended float switch, it will go with the flow, as far as the cable allows! While cable-suspended float switches are all mechanically pretty equivalent (float and cable), they can be much more electrically diverse than stem-mounted float switches. Cable float switches can be simple, with a single point that controls a switch, or more complex, with up to four switch points and built-in hysteresis.
How do Float Switches Work?
Almost all electrical float switches work by using a magnet to open and close a reed switch.
How Stem-mounted Float Switches Work
Stem-mounted float switches use a magnet in a float that passes over the reed switch with the rising or falling action of the liquid, either opening or closing the switch. On horizontal stem-mounted float switches, the float rotates away from the reed switch on a hinged arm, rather than free-floating on a central stem.
How Cable-suspended Float Switches Work
Cable-suspended float switches have both the magnet and the reed switch located in the float. As the float rises and falls with the liquid level, the magnet moves closer to or further away from the reed switch, causing it to open or close. In both cases, the changing liquid level is translated to an electrical on-off signal by the movement of the magnet.
Normally Open vs. Normally Closed Switches
The trickiest part of float switches is figuring out whether a situation calls for a Normally Open or Normally Closed switch. “Normally” refers to the lowest position the float can be in where the float is not floating. “Open” means an open circuit, which is off. A “Closed” switch completes a circuit, turning it on. So, for any given application, think about whether you want rising or falling liquid level to trigger an action, and whether that action should be turning a circuit (think a pump, or an alarm) on or off. A normally open switch will turn OFF a circuit as liquid level falls. A normally closed switch will turn a circuit OFF as liquid level rises. For example, if you want your float switch to trigger a low-level alarm, you would use a normally closed switch. However, if you need to turn off an emptying pump when the level in a tank or reservoir gets too low, then you would use a normally open switch.
It is important to know whether you need a normally open or normally closed float switch because most float switches come with the normally open or normally closed operation selected at the time of purchase. There are some single-point stem-mounted float switches that are user reversible.
Float Switch Setup and Installation Best Practices
Some float switches are “plug and play”, and most are fairly easy to install, but it’s worth taking a moment to go over some best practices for setting up and installing float switches.