Radar Sensor Frequently Asked Questions
Radar sensors are commonly used for a wide variety of vehicle detection and collision avoidance applications, and they are a particularly excellent choice for outdoor deployments. Keep reading to learn more about radar sensors and see answers to frequently asked questions.
Q. What are radar sensors?
Radar is an object detection system using radio waves. The benefits of radar include:
- Reliable outdoor use. Radar sensors are resistant to wind, falling rain and snow, fog, and sunlight. They are less affected by temperature fluctuations and operate in a wider range of temperatures than competing technologies.
- Long sensing range for flexible mounting.
- More durable and less downtime than other technologies.
Banner's radar sensors utilize Frequency Modulated Continuous Waves (FMCW). FMCW radiates continuous transmission power and changes its operating frequency during the measurement. FMCW measures the frequency shift between emitted and received signals. FMCW radar can detect both moving and stationary targets (doppler cannot see stationary targets).
Q. What do the different frequencies do?
Banner offers two different radar frequencies: 24 GHz and 122 GHz. The 24 GHz has a longer range and is most immune to ambient weather, but has a much coarser accuracy. The 122 GHz has higher precision, can see a wider range of targets, and is resistant to ambient weather.
Q. Where should I use a radar sensor?
Radar sensors are an ideal solution for applications where you need to detect a vehicle or avoid a collision when moving equipment. For example, radar can be used for:
- Vehicle detection--including cars, trucks, and trains--in traffic & parking applications, toll booths, loading docks, drive-thrus, shipping canals, and railroads
- Collision avoidance in ports and manufacturing (i.e. overhead and gantry cranes)
- Collision avoidance for on-board mobile equipment (i.e., reach stackers, forklifts, and mining vehicles)
- Collision avoidance in low-visibility factory environments (i.e., overhead bridge cranes)
- Level measurement while looking through steam or dust where ultrasonic might struggle
- Provide reliable position feedback (i.e., reach stackers or ground support equiptment like baggage handlers or de-icing vehicles)
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Q. What objects can radar sensors detect?
The objects a radar sensor can detect depends on the operating frequency of the sensor and the dialectric constant of the material. Lower frequency sensors (24 GHz) require a higher dialectric constant, such as metal or large amounts of water. Higher frequency sensors (122 GHz) can see much more, including non-ferrous targets glass, wood, or other organic materials.
Q. Does the target have to be moving for a radar sensor to detect it?
No, radar sensors from Banner Engineering use Frequency Modulated Continuous Wave (FMCW), which can detect both stationary and moving targets. Moving targets do provide more powerful reflections compared to stationary targets.
Q. Can radar detect people, or will nearby people interfere with sensing the target?
A higher frequency radar sensor (122 GHz) will more reliably detect people but is not intended to be used in personnel detection as a safety rated device. Depending on sensor sensitivity settings, a person could interfere with sensing the intended target if a person is near the sensor and within the sensor's direct field of view.
Q. What is the difference between adjustable field and retro-reflective radar sensors?
An adjustable field (diffuse) radar sensor can detect vehicles and other objects by sensing the reflection of the radio waves bouncing off the object. Optimal targets include:
- Large metallic objects that reflect a lot of radio waves, a property referred to as a large “radar cross section.”
- Objects that have surfaces that are perpendicular to the radar beam pattern to reflect the radio signal directly back to the sensor.
Adjustable field radar sensors have configurable “set-point distances,” where the sensor will use the time between emitted pulse and reflected signal detection to calculate how far away a sensed object is from the sensor and only turn the output on when the object is within the set-point distance.
A retro-reflective radar sensor uses a taught reference condition like a wall, floor, or special retro-reflective target. The sensor detects objects between it and the reference target by looking for disruptions in the signal coming back from the reference target.
This type of sensing can sense objects even if they do not have a good radar cross section, but they must block the signal reflection from the reference target. This makes retro-reflective radar sensors the most robust radar sensing option.
The QT50R has a separate retro-reflective model, however any T30R sensor can be configured as a retro-reflective sensor by setting a distance window around a reference target.
Q. What is the dead zone for radar sensors?
24 GHz radar sensors from Banner have a typical “dead zone” of 0.4 meters for moving targets and 1 meter for stationary targets. What this means is different depending on whether the sensor is adjustable field or retro-reflective:
- Adjustable field sensors - the sensor cannot reliably sense objects within the dead zone, but it is still possible.
- Retro-reflective sensors - the retro-reflective target cannot be placed within the dead zone, but an object within the dead zone can still be sensed because it interrupts the signal from the reflector target.
122 GHz radar sensors have a 150 mm dead zone for detection and 300 mm dead zone for an analog measurement.
Q. Can radar sensors have two independently set outputs?
Yes, depending on the series. Most radar sensors from Banner Engineering have an option with two zones with an independent output for each zone.
Q. When would I use a radar sensor with two zones?
It is common to use two zones in a collision avoidance applications. For example, one long-range zone can be used as a “slow down” signal, and the other short-range zone can be used as a “stop” signal. Two zones can also be used to determine if the object is getting closer to or farther away from the sensor.
Q. Can radar sensors tell me which way an object is moving?
Yes, by using two zones or an analog output, the radar sensor can tell which way an object is moving. But it can only determine if the object is getting closer or farther away, not if it is moving left or right.
Q. Are there analog radar sensors?
Yes, the Q240 radar sensor and the T30R have analog versions that can be used for long range distance gauging (for example, port applications where the position of the crane needs to be measured).
Q. Can radar sensors be used outdoors?
Yes, radar sensors can be effectively used outdoors. The housings are rated IP67 for reliable operation in harsh environments.
Q. Is radar susceptible to rain, snow, sleet, sand, or other weather conditions?
Radar sensors are resistant to extreme temperatures, falling snow, fog, heavy rain, humidity, and strong wind. They are also immune to error from sunlight. They have no moving parts and are resistant to vibration from nearby traffic and heavy machinery.
Weather shields are also available to prevent rain/snow accumulation on the face of the sensor. The sensor can be placed in special fiberglass enclosures (radar can transmit through some materials) if the application requires it.
Sensitivity or signal strength threshold adjustments can also be used to further ignore harsh ambient conditions.
Q. What is a radar sensor's beam pattern?
The beam pattern for each sensor is defined by its antennae and remains constant.
Q. How wide is a radar sensor's beam?
The effective beam pattern chart for each sensor is provided in its datasheet. If the sensor’s beam pattern is too wide, consider using a narrow-beam sensor. The effective beam width varies with the sensor, the distance to the target, the radar cross section of the target, and the sensor’s sensitivity (signal strength threshold) setting.
Q. What does adjusting the sensitivity (signal strength threshold) do?
Changing the sensitivity of a radar sensor can be used to ignore unwanted weak targets within the field of view of the sensor (focusing the beam on the main target you want to see vs. smaller objects in the beam path). This is especially useful to ignore heavy rain with the T30R.
Q. How should I mount a radar sensor to account for beam width?
When mounting the sensor, consider both the vertical beam pattern and the horizontal beam pattern. You may want to rotate the sensor 90 degrees to reduce the field of view of the sensor to ignore unwanted reflections.
Q. Can you locate two radar sensors next to each other without cross talk issues?
Yes. Radio waves travel at the speed of light. Each radar sensor knows when it should be receiving the radio pulse reflected from its target and is generally resistant to crosstalk.
Q. Can radar detect liquid levels in a tank?
The T30R can be used to detect liquid level in a tank and has an added benefit of a longer range than ultrasonic to work larger tanks.
Q. What might help to fix a chattering/flickering/intermittent output?
If a radar sensor's output is chattering when the target is fully within the field of view of the sensor, you could increase the response speed and/or the sensitivity of the radar sensor to make the output more consistent.
Q. Can I use radar sensors in my country?
Banner's radar sensors are certified for use in many regions including the United States, the United Kingdom, Europe, China, Australia, New Zealand, and more. Additional approvals are pending. Contact Banner Engineering with specific requests.
Q. How do I choose a radar sensor model that is approved in my country?
Country certifications are listed in the product datasheets. Contact Banner if you do not see the country needed.
With recent FCC changes, we can now offer EU models in the US and other countries. EU models use a wider frequency bandwidth to achieve shorter dead-zones. If you have specific questions, please contact Banner Engineering.
The T30R sensor is a longer-range alternative to ultrasonic sensors, and provides more reliable detection and position feedback in extreme outdoor conditions and other challenging environments. It features a shorter dead zone, better accuracy, and the ability to see a wider range of targets than traditional 24GHz radar sensors.
Radar sensor with narrow and wide beam options to detect moving or stationary targets in all weather conditions. Graphical User Interface provides simple setup, greater control, and visibility into sensor settings.