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Is Your Ultrasonic Level Sensor In Level Or Distance Mode?

water level gauge on a concrete wallUltrasonic level sensors measure distance. It’s the nature of the technology. But with relative ease, you can tell your sensor to measure level. All it requires is changing your output.

So what is your ultrasonic sensor measuring? Is it giving you a distance or a level? If you’re not sure, this article is for you.

The Difference Between Distance And Level

This isn’t a concept we think of regularly, but there is an important distinction between distance and level. Understanding the difference is central to how you set up your ultrasonic sensor.

Distance measures how far away a surface is from the sensor. Level tells you how far away a surface is from the bottom of a tank, pit, or well. Like most things conceived by engineers, the world of measurements is a nuanced one where details make all the difference. This is a prime example.

If your sensor’s output is set for distance and your control system is looking for a level, you’re going to have problems. Program your sensor to match your control system settings so the two will be speaking the same language.

Setting Up The Output

To change your sensor from distance mode to level mode, or vice versa, you need to set the sensor’s output. For a 4-20mA output sensor, this means setting the 4mA and 20mA signals to either full or empty. If 4mA is full and 20mA is empty, you’re in distance mode. If 4mA is empty and 20mA is full, you’re measuring a level.

For a Modbus sensor, or one of our older sensors with a proprietary output, you simply change a setting, such as the “Application Type” to either distance or level.

This defines how the reading is calculated. As long as it matches what your control system is expecting, you’re all set.

How Do I Know When I Have A Problem

If your control system and sensor are in opposite modes, you’re reading will be an inverse to what’s expected. The only time it will read right is when your level is at 50%.

You can imagine how this would throw off your controls.

The good news is it’s a simple fix and relatively easy to recognize. You might feel a little silly if this happens to you, but hopefully it’s at the test bench where simple programming snafus are relatively commonplace.

If you’re ever troubleshooting one of our ultrasonic sensors, keep in mind that distance mode is the factory default. If you need level mode, but want to do a factory reset as part of your troubleshooting (a really good idea if you’ve narrowed it down to the sensor), remember to switch back to level mode or you’ll have a hard time making other adjustments.

We’re only a phone call/email/live chat away, so contact us if you’re having any trouble.


Need an ultrasonic level sensor that works for you, not against you? Get one that you can program to fit your application! Learn more below:

top image credit: Faisal Akram via flickr cc cropped

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