Get answers to frequently asked questions about sensor applications, including compatibility, installation, and troubleshooting. Count on APGSENSORS for expert support and tailored sensor solutions.

Turbulence is a tricky challenge that may require a few extra steps. For ultrasonic sensors and continuous float level transmitters alike, you can install a stilling well. This is a tube that extends from the sensor mount to the bottom of the liquid. A hole is drilled at the top of the tube that allows air to escape and the liquid to rise up the tube at the same level as the main body of liquid. While the liquid in the tube is the same level, it is buffered from any turbulence - hence the name "stilling" well.

Another good way to do this is to use a submersible pressure transducer. While they're not a good solution for a blending tank, they are unaffected by turbulence at the surface.

Most of our sensors operate somewhere within the -40° to 180° F window. However, some of our float switches are capable of working in heat up to 392° F. If you need a sensor in temperatures close to it's limitations, there are still a few options. In hotter temperatures, you may be able to use a stand pipe or a heat sink to cool hot temperatures just enough before they reach the sensor to allow accurate measurement. In colder climates, you may need to install the sensor inside of a box or a housing with a heater installed.

Chemical compatibility must always be verified before you purchase a sensor. This is incredibly important to ensure safety. That said, we do have sensors that can work in caustic chemicals. The materials we use for our sensors include 316L Stainless Steel, PVC, and Nickel Alloys. Just make sure you check chemical compatibility. If you're unsure, give us a call and we'll check for you.
Making interface level measurements are tricky. This is often considered one of the most difficult liquid level measurements out there. And we're proud to have a very reliable solution. Our MPX continuous float level transmitter uses magnetostrictive technology to detect a float that sits right at the interface of the two liquids. It simultaneously detect the float at the top as well, so you can get both a total level and an interface level on the same sensor. It can even provide a temperature reading. This probe is used extensively in the oil and gas fields where oil and water are stored in the same tank.
In lightly pressurized tanks, you can use a standard sensor - as long as the pressure in the tank does not exceed the rating of the threads. For our ultrasonic sensors, that's only about 30 psi. However, if you have a lot of pressure inside a tank, or highly variable pressure, you should use differential pressure. This is done by measuring the liquid column with a pressure sensor at the bottom, and measuring the gas pressure with a sensor at the top. You simply subtract the gas pressure from the liquid pressure, and you'll be able to calculate a level.
Pressure range is the range within which a pressure sensor can accurately measure. Pressure rating refers to the physical limitations of a sensor's process connection. For example, a 1502 wing union connection can hold at 10,000 psi, but it's not rated for 15,000 psi. So we can calibrate our 1502 Hammer Union Pressure Transmitter to 15k psi, but we do so with a warning - the fitting isn't designed for that pressure range. This is incredibly important. Don't confuse the pressure range of the sensor for the pressure ratings of the fitting. If you do, you might end up with a projectile, or even an explosion.

If you want the right pressure type, you need to understand what they are, how they measure, and why they're used. There are five pressure types:

  • Gauge

  • Compound

  • Vacuum

  • Sealed

  • Absolute

Gauge pressure measures everything above atmospheric pressure. It considers the pressure of the atmosphere as zero pressure - just like you do. This is widely used, and definitely the most popular type amongst the pressure sensors we sell.

Compound measures above atmospheric and below atmospheric - all the way to vacuum. This pressure type is useful when you need to see positive and negative pressure. However, there are usually good reasons to use the Absolute pressure type instead (see below).

Vacuum pressure measures from atmospheric pressure to vacuum. It's only measuring the vacuum. This is useful when you want to compare a negative pressure to atmosphere.

Sealed pressure uses the atmospheric pressure at the time it was sealed as it's zero point. This comes with it's own set of difficulties at lower pressure ranges. But it's great for higher pressure where the minute differences in atmospheric pressure don't matter.

Absolute pressure is also sealed, but under a full vacuum. It's zero point is true, or absolute, zero. Even vacuum pressures are seen as positive pressure to the absolute pressure sensor. This is often a better choice than compound because your reference point is fixed. It's also the basis of many calculations, such as head and resistance calculations in pump systems. Using an absolute pressure gauge on your pumps reduces the conversions needed to make use of your measurements.

To know which type you should use, you need to understand your goals. You should also understand what types of conversions you would have to do once you have a measurement. It's also hepful to know that sealed pressure sensors are better for dusty or moist environments. In many cases, you would do yourself some good to use an Absolute pressure sensor as long as you know how to interpret it properly.

If the explanations above aren't helping you, please contact us so we can discuss your application and get the right sensor.

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