Measuring fluids, and doing so with precision is exactly what float switches and level sensors were created to do. Regardless of the application, their ability to measure and identify the presence or absence of a liquid in a vessel is critical.

There are, however, some factors to take into account when selecting the proper level sensor or float switch – one of the most important being the type of liquid being measured.

Is it corrosive? Thick? Hot? These elements can affect how measurements are taken.

For this post, we’ll be focusing on viscosity and how highly viscous (thick) liquids (think oil, paint, molasses) present a unique challenge for measuring.

Why High Viscosity is an Issue

Viscosity is used to describe how thick a substance is and defines its ability to change shape under stress or tension. To give you a better idea of different viscosity levels or centipoise (cP) measures, water measures at 0.894 cP, castor oil at 650 cP and ketchup at 50,000 – 100,000 cP.

As you can see the “thickness” plays a major role in how freely these different fluids can flow.

When trying to get an accurate measurement you cannot use the same float switches or liquid levels in every situation. Problems including the float getting stuck or even damaging the pressure ports are all possible.

Keep in mind too that temperature conditions can change viscosity levels so be sure you’re selecting a solution that is most compatible with your specific application.

The Solution

The best option for high viscosity liquids is to opt for non-contact options like optical or ultrasonic level sensors for accurately measuring liquid levels.

Here’s why:

Acoustic waves emitted by ultrasonic liquid level sensors and the measuring of the echo returned, make it possible to know liquid levels without ever having to physically touch the matter – eliminating the risks mentioned earlier.

With optical switches, measurement is done using a laser wave or forward light scattering and a probe. There are no moving parts and the option works well because it can measure the presence or absence of many different types of liquid.

Need help choosing the right solution for your application? Let SMD Fluid Controls help. We work to lower costs and increase productivity for all of our clients, offering competitive pricing for OEM designs and applications.


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