Generally, ultrasonic liquid level gauges do not require pilot tubes because their emission angles are not large. Unless there are some special circumstances.
Why do you have to use a pilot tube?
-----Supplementary information
1. It is recommended that you raise the probe to increase the distance from the water surface. For example, you can raise the probe to a height of 3 meters
As long as your measuring range is sufficient.
2. It is recommended that you replace the probe with anti-condensation function. Or simply switch to radar.
3. A simple guide tube may not ensure no condensation
--Further addition
The original purpose of installing a guide tube is to measure in a long and narrow space In use, the waves are more concentrated and more directional.
I can tell you for sure that ultrasonic plus guide tube is also possible. As for the anti-condensation effect, it cannot be guaranteed.
What you need to pay attention to is that the guide tube should not be too long, the surface should be smooth, and there should be no burrs on the edges. Regular and neat.