Radar level transmitters and ultrasonic level transmitters use the time-of-flight measurement principle. Both have their own strengths and applications, and if you are thinking of purchasing one, you should think carefully about which one you need. This article will tell you the pros and cons of each to give you a headstart, but if you are still undecided by the end, feel free to give us a call.
Ultrasonic level transmitter vs radar level transmitter
Ultrasonic level transmitter
In my opinion, ultrasonic level transmitters are becoming 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 vapour 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 vapour 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.
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.
If you need help picking the right level measurement device for your application, take a look at our new level smart assistant.
To know more about level transmitters, please ask our engineers!