Well, without more details on your process and tank, we can’t recommend an ultrasonic or radar level transmitter with certainty. Both measuring principles work using the time-of-flight concept. If you want to know more about that, then you can read this post here. However, we can highlight the pros and cons of each, and you can figure out the best solution based on those.
Ultrasonic level transmitter vs radar level transmitter
Ultrasonic level transmitter
In my opinion, ultrasonic level transmitters have become obsolete. Sure, many brands still push this tech. But with the low-cost radar level transmitters now available, it’s hard to justify. Still, it may be too early to declare the ultrasonic dead.
Anyway, an ultrasonic level transmitter uses a piezoelectric sensor to emit mechanical waves. As a non-contact level transmitter, it has a simple design compared to other level devices. Unfortunately, it also has a dead zone or blocking distance, a specific length where the device won’t measure. And vapor and foam can cause it to work incorrectly.
In the figure above F is the full distance in which the measurement takes place, E is the total distance between the sensor and the sensor mounting flange and the lowest measurable level of the full range. L is the portion of E currently filled with product,D is the portion of E that is empty,and BD is the blocking distance. Most radar sensors have a minimum distance between the maximum level and the mounting
Radar level transmitter
Now, radars work with electromagnetic waves, also known as microwaves. If you need a non-contact solution, then you can use a free space radar, whereas a guided radar has the antenna in constant contact with the product. Some vendors say you can apply a radar level transmitter in products with foam and vapor and such, but your mileage may vary on those.
Regardless, changing the working frequency will change the beam spread, making the installation easier in some cases. And a radar measures everything inside the tank, unlike the ultrasonic that stops at the product’s surface.
The following video explains the principles of radar level measurement:
As for the drawbacks? Well, most radar level transmitters cost more than ultrasonics, although VEGA and Endress+Hauser have a few low-cost options. They take a little more work to set up as well and need a liquid with a minimum dielectric constant.
So, do let us know which one will work better for you.