Types of Contact-Level Measurement
There are many different types of contact-level measurement systems, so before we explore their benefits, let's briefly touch on each.
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Float switches
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Displacers
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Conductive/resistance monitoring
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Optical switches
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Bubble tubes
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Level sight gauges
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RF capacitance
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Contact ultrasonic
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Magnetic transmitters
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Interface sensors
What are the benefits of using these contact-level measurement systems over remote systems that don't need to touch the surface of the material?
Accuracy
While non-contact measurement systems can be accurate, they often need recalibration to ensure they're providing the correct information. Most contact-level measurement systems are straightforward — for example, float switches are nothing more than a float attached to an arm. It's the same technology that controls your car's fuel gauge. Other variables that could affect a non-contact reading, like foaming, don't influence them. These simple devices can also provide accurate readings in many different substances, from liquids to solids or small particulates without any additional calibrations. That's something not even guided wave radar sensors can do.
When two liquids of different densities are in the same tank, non-contact systems can't measure them accurately. Interface sensors could tell you how much total liquid is in the tank, but don't know where the two different fluids separate or the level of the bottom liquid.
Durability
One of the best things about contact measurement systems is their simplicity. They usually don't have a lot of moving parts, which means they require less maintenance and are infinitely more durable than non-contact systems. Their simplicity also means if an element does fail, it's often easy to replace without having to empty the tank or interrupt the supply chain.
This feature is valuable in the process industry, especially if the materials stored in the tank are caustic, corrosive or otherwise too dangerous for human workers to enter to effect repairs. Many industries use acid in various concentrations for a variety of different tasks. Even when empty, an acid tank may be too dangerous for a maintenance worker to enter, even with the proper personal protective equipment.
Customization
Not all measurement systems are equal, but that isn't a bad thing. Some contact-level measurement systems will only work for liquids, while others can work for liquids, particulate matter and slurries with equal accuracy. These measurement systems are easy to customize for different materials. Many contact measurement systems won't work well for corrosive or sticky materials — an optical switch, for example, might not work well in oil because the sticky substance will cover the prism and prevent it from transmitting light.
This customization also makes it simpler to connect multiple different types of systems to a single readout so workers can monitor the levels remotely without having to make a trip to each tank. If you've got containers of oil, acid and water in the same facility, you don't need to use the same system for each of them, but link them on one readout for ease of monitoring.
Ease of Use
We've already mentioned simplicity and durability as a benefit, but this simplicity also makes these devices more straightforward to use. There is no need for fancy calibrations or complicated training when your measurement system is nothing more than a float attached to a magnetic reed.
This uniformity also reduces the chance of a misunderstood reading. For simple measurement systems that aren't part of a computer system, this is vital because you will be relying on human workers to ensure the levels are correct. Incorporating humans into the system always raises the risk of a mistake or a typo, and that risk becomes more pronounced once you start using more complicated non-contact-level measurement systems.
Use Contact-Level Sensors to Your Advantage
Not all contact-level management sensors are the same, and there may be some situations where non-contact systems are necessary. Don't let this turn you away from using non-contact measurement tools where applicable. The simplicity of the ones we've mentioned above may be tempting, but you need to find the right tool for the job, not just the one that might seem to be the easiest.
Contact-level management sensors are a necessary part of fluid and granular storage, and every industry that has one or more storage tanks on their property uses them. While non-contact sensors have their applications, contact systems are more accurate and require less overall maintenance.
