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Radar sensor tutorial: Distance measurement with radar sensors

Our radar tips for the optimal use of radar sensors for distance measurement.

OndoSense radar sensors for distance measurement can be used successfully in many industries and applications. For optimal use of our radar distance sensors, we have summarized the most important practical radar tips in this tutorial for you. Get the best results quickly with radar sensor technology for distance measurement in your industrial environment – with our radar sensor tutorial!


Smart radar sensor for distance measurements.

OndoSense reach. Compact. Reliable. Outdoor-proof.


High-precision radar distance sensor.

OndoSense apex. Ultra-precise. Fast measurements. Very robust.

1. Correctly align radar sensor to target object

Align radar perpendicularly to object

If you start operating your radar distance sensor for the first time, you will see how important it is to correctly align the radar sensor to the target object. Assuming an object with a flat surface is facing the radar, the following applies: The more precisely this surface is aligned perpendicularly to the center of the radar beam, the stronger the radar sensor signal.

Radar tip #1

To get a strong signal, align the radar sensor as far as possible at a right angle to the target object.

With increasing tilting of the surface or object, the signal strength of the radar sensor decreases, as the radar radiation is increasingly not thrown back to the radar distance sensor. The roughness of the surface also plays an important role: The rougher the surface, the higher the degree of tilting that just allows a stable radar signal.

For smooth surfaces, on the other hand, the maximum possible tilting is lower, because the radar beams are more scattered and reflected in different directions. Radar sensors are therefore better suited to detect objects with very rough surfaces in comparison to laser sensors.

Radar tip #2

The smoother the surface, the more important the correct alignment of the radar sensor.

2. Measuring spot size: Key factor for stable, precise measurements

Small radar measuring spot for precise measurements

The measuring spot size of the radar distance sensor, which depends on the opening angle, has a large influence on the detection of the target object and possible interference reflections, similar to optical systems. A large opening angle leads to a large measuring spot, so that the distance measurement of the radar sensor is averaged over a wide range of the measuring object and the distance measurement becomes inaccurate.

A larger radar beam also leads to more interference reflections as well as to a weakened receiving signal at equal transmitting power. The radar distance sensor is thus less able to distinguish small or distant objects from the background.

Radar tip #3

Try to measure closer to your target object to reduce the measurement spot and avoid potential interference reflections.

A small aperture angle leads to a small measuring spot size, which leads to fewer interference reflections, especially for small or far away target objects. This enables reliable distance measurements with strong receiving signals and higher accuracy. At the same time, a small opening angle reduces the maximum tilting rate at which a stable radar sensor signal is possible.

Radar tip #4

Choose a radar sensor with a narrow opening angle to achieve precise and reliable measurement results.

The measuring spot size is an important parameter for distance measurements with radar sensors. With the OndoSense radar spot size calculator, you can calculate the measurement spot size of your radar distance sensor (depending on the distance from the target object) in just a few clicks! Just select your OndoSense radar sensor or enter the opening angle and lens diameter of your radar sensor for distance measurement.

Radar tip #5

Calculate the measuring spot of your radar sensor for your distance measurements, e. g. with our radar spot size calculator.

3. Radar sensor resolution: Distinguishing objects from each other

Radar resolution: distinguishing between several objects

The resolution is a crucial parameter of radar distance sensors. It is of great importance when it comes to the question of the suitability of the radar sensor for a specific measurement challenge. The resolution indicates at which distance from each other two objects are detected separately by the distance radar. Only if the radar signals (so called peaks) of these objects can be clearly distinguished from each other, the distance of both objects may be determined.

This is relevant if several objects are located at a similar distance from each other and are detected by the radar sensor for distance measurement. For example:

  1. The objects lie next to each other and are both detected by the opening angle of the radar sensor or covered by the radar spot. In addition, the first object does not completely cover the second object. One possible application is the width measurement of a thin steel strip, which moves on a roller conveyor and is detected laterally by the distance radar. The distance value to the steel strip can be clearly determined if the distance from the steel strip to the rolling gear corresponds at least to the resolution of the radar sensor.
  2. The objects are in a row. The first object is partially permeable for radar waves, i. e. it is made out of a non-conductive (dielectric) material such as plastic, rubber, cardboard, etc.

Radar tip #6

Pay attention to how many objects your measuring spot covers and which objects are relevant for your distance measurement.

If the radar distance sensor cannot detect two or more target objects separately and thus resolve them, then the distance to neither object can be reliably determined. A powerful distance resolution therefore has many advantages and is in some cases necessary.

Radar tip #7

If you want to detect objects that are close to each other, your radar sensor should have a good distance resolution.


Smart radar sensor for distance measurements.

OndoSense reach. Compact. Reliable. Usable outdoors.


High-precision radar distance sensor.

OndoSense apex. Ultra-precise. Fast measurements. Very robust.

4. Averaging of distance value for multiple objects or complex surfaces

Radar averages distance values of complex surfaces

In certain cases, the opening angle of the radar sensor detects several objects or structures with a complex surface gradient – e. g. in contrast to a flat surface. If the distance between the reflection points of these objects or structures is smaller than the resolution of the radar, the radar sensor can no longer detect the different distance values. The result is an averaging of the distance values of all detected reflection points.

Radar tip #8

Consider whether your measurement value results from the averaging of the distances of different reflection points in the radar opening angle.

The stronger the reflection at a specific position of the object or surface, the higher the weight of this reflection point in the displayed distance value of the radar sensor. If the surface curve of the measuring object is known, the measured distance can be corrected to detect the exact distance value. This is the case with round objects or surfaces, for example. If necessary, OndoSense provides support in the development of a radar algorithm for correct distance calculation.

Radar tip #9

If you want to capture the distance to complex surfaces with very high precision, you may need to correct the measured distance value

5. Radar penetrates non-conductive materials

Radar penetrates non-conductive objects

Using a radar sensor, it is possible to penetrate non-conducting materials such as plastic, rubber, cardboard, glass, etc., since the radar waves only partially reflect these dielectric materials. On the other hand, when the radar sensor beams encounter metals or continuous water films, they are fully reflected.

Radar tip #10

Radar allows you to measure through non-conductive materials. For more information, take a look at our overview table:

Being able to penetrate certain substances or objects with radar distance sensors makes sense for a wide range of applications:

Radar sensors can detect the distance to objects behind glass, plastic or other non-conducting materials. At the boundary layer of the dielectric material there is a weak reflection, which also determines the distance to the glass or plastic. However, most of the radar waves radiate unhindered through this material, so that the distance to the target object behind it is detected.

To protect the radar sensor from enormous heat radiation or explosions, glass, heat-resistant plastic or a mica plate can be used. Only a limited amount of the radar signal is reflected, so that the radar sensor detects the distance to the object behind it with high accuracy.

Radar tip #11

Do you need to protect your sensor from great heat? Radar also measures through heat-resistant plastic windows!

6. Radar reflector for amplified radar signals

Relfection principle of radar reflectors (also called corner cubes)

Radar reflectors are mirror-like retroreflectors that ensure that the radar beams are always thrown back in the direction of the radar distance sensors regardless of the direction of incidence. Even at a small size, a radar reflector can reflect a relatively high amount of energy due to the large effective reflective surface (also called radar cross section).

Radar reflectors usually consist of three surfaces arranged perpendicularly. Due to the resulting cube shape, they are also referred to as angle reflectors or corner cubes. The advantage of these three-surface radar reflectors is that the radar beams are accurately reflected back to the radar source even if there is no right angle orientation to the radar sensor.

Radar tip #12

You cannot align your target object right-angled to the radar? Consider using a radar reflector.

With the help of radar reflectors, the precision of distance measurement can be significantly increased. In addition, reliable distance measurements over long distances can be realized, as the radar sensor signal is significantly amplified by the enlarged radar cross-section.

Radar tip #13

Use a radar reflector to increase the stability or precision of your measurement.

Radar reflector for precisely measuring longer distances

Radar tip #14

At long distances, you can significantly increase the range and signal strength of your measurements with a radar reflector.


Smart radar sensor for distance measurements.

OndoSense reach. Compact. Reliable. Usable outdoors.


High-precision radar distance sensor.

OndoSense apex. Ultra-precise. Fast measurements. Very robust.

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