Ultrasonic Continuous Level Transmitter Accuracy

Gems UCL (Ultrasonic Continuous Level) series, which includes the UCL-510 and UCL-520, both provide a linear output signal of 4-20 mA scaled to match a level measurement value. UCL-510 level range is up to 1.25 meters (49.2”) for small tanks. The UCL-520 covers mid-sized tanks with a range of 1.8 meters (6’) to 8 meters (26.2’). Product specifications call out the accuracy for these devices as shown below.




Accuracy refers to the possible offset between the measured and actual level value. It is not an overall offset, but rather the offset possible at any given level. The accuracy of the UCL-510 is ± 3mm for the entire measuring range up to 1.25 meters. This means if the actual level is 0.75 meters, the UCL-510 will read from 0.747 m – 0.753 m. All but the most critical applications can utilize this highly accurate sensor. The UCL-520 accuracy varies depending on the measuring span the device is programmed for. This is due to the wide measuring range available and the operating principle of ultrasonic sensing. Ultrasonic sound waves are emitted from the sensor. They bounce off the surface of the liquid and return to the sensor’s receiver. Distance is calculated based on the time for the round-trip from emitter to receiver. Therefore, accuracy can be affected slightly by distance (UCL-510 distance is too short for noticeable change).




The empty to full span is programmed into the UCL-520. The accuracy will be ± 0.2% of that value. When your tank is 0 - 5.5 meters from empty to full the accuracy will be ± 11 mm (1.1 cm, 0.43”) for any measurement along the entire measuring range. So, if that tank is at 3.3 m, then the UCL-520 will read about 3.29 - 3.31 meters. It is also an extremely accurate sensor good for almost any application requiring precise liquid level measurement. It is important to note that accuracy specified here is dependent on the sound waves traveling through clean air. Other gases, in a vacuum, or air with high amounts of contaminants (dust, vapors, etc.) can affect measurement.

Another specification which is often mistaken for accuracy is resolution. Resolution is what determines how smooth the output will be. It is the smallest measurement the device can sense reliably. See the visual example below:



Choosing the right ultrasonic level sensor involves reviewing accuracy and resolution to insure it meets your application requirements. Gems UCL series provides high accuracy and high resolution suitable for the most precise non-contact liquid level sensing applications.


More on Gems UCL-510 and UCL-520 HERE.