In modern multi-storey and underground car parks, the automatic recording of free and occupied parking spaces has long been standard. Intelligent sensor technology plays a central role in this: It must reliably detect whether a parking space is occupied by a vehicle under difficult conditions such as dust, darkness, changing surfaces or moisture.
This was precisely the challenge faced by an electrical installation company that was looking for a sensor solution for parking space monitoring in underground garages for a parking garage. Two types of sensors were considered: the ultrasonic distance sensor U1RT002 and the optical laser distance sensor P1KY101. Both systems fulfilled the basic measurement task – but the environmental conditions in the underground car park tipped the scales.
The challenge: Reliable detection despite dirt and darkness
In underground car parks, sensors are exposed to special influences: dust, moisture, fine dust particles and changing light conditions often make the work of optical systems more difficult. Especially in dark or matt paintwork, the vehicle surface partially or completely absorbs the emitted light – the sensor signal is too weak, and the parking space is incorrectly recognized as “free”. In addition to high accuracy, the customer was therefore focused on one thing above all: absolute reliability regardless of color, gloss or dirt.
Solution 1: Ultrasonic distance sensor U1RT002 – the robust choice for parking lot monitoring in underground garages
The ultrasonic distance sensor U1RT002 detects objects based on sound waves instead of light. This means that it works completely independently of color, material and reflective properties, which is a decisive advantage for applications with vehicles with different paint finishes. With a scanning range of 100 to 1,200 mm and a compact cubic design, the U1RT002 is ideal for wall or ceiling mounting. The sensor periodically emits ultrasonic pulses and measures the travel time of the reflected sound waves.
This means that the distance is calculated precisely, regardless of whether the vehicle is black, white or glossy metal. Another plus point: the ultrasonic sensors clean themselves of dust and dirt particles by vibrating, which minimizes maintenance and extends service life.
Advantages of the U1RT002 at a glance:
- Color, gloss and material of the vehicle do not matter
- Insensitive to dust, dirt and ambient light
- Low maintenance due to self-cleaning transducer
- Compact format with flexible mounting concept (wall or ceiling)
- Reach up to 1,200 mm – ideal for parking lots and driveways
Solution 2: P1KY101 laser distance sensor – precise, but dependent on the environment
The P1KY101 Laser Distance Sensors Time of Flight is an optical alternative based on Time-of-Flight (ToF). It measures distances over the propagation time of laser pulses and achieves a high repetition accuracy of up to 1,500 mm – but only up to around 700 mm for dark surfaces. For applications with clear visibility, the P1KY101 offers excellent precision. In underground car parks, however, dust, mist or reflective scattered light can impair the signal. For this reason, the decision in this application was made in favor of the ultrasonic variant, which is more robust in such environments.
Why ultrasound was the better choice
When it comes to monitoring parking spaces in underground garages, process reliability is what counts first and foremost. The system must function reliably for years, regardless of vehicle type or lighting conditions. Ultrasonic technology offers exactly that: contactless, color-independent detection, combined with high stability and low maintenance.
Conclusion
Whether it’s a multi-storey car park, underground car park or test facility, reliable vehicle detection is only possible with the right technology. While optical sensors such as the P1KY101 score well in clean conditions and bright environments, the ultrasonic distance sensor U1RT002 delivers reliable results even under difficult conditions. It measures precisely, regardless of paint color or dirt, and thus ensures stable detection – durable and low-maintenance. This makes ultrasonic the ideal solution for parking lot monitoring systems where reliability is important instead of visibility.
