FAQ on Laser Sensors for Distance Measurement
General Questions
With the parameters “Distance range close” and “Distance range far”, certain areas of the working range can be hidden. No signals are evaluated in these areas. This means that a glass disk, for example, which the sensor looks through, is hidden. The “Distance range close” is placed behind the disk for this purpose. If there are interfering objects in the background, the max. working range can be reduced by reducing the “Distance range far”.
Laser distance sensors use laser beams to measure the distance between the sensor and an object. Distance sensors measure distances according to the triangulation principle or according to the time-of-flight method depending on the working range and accuracy.
The choice between a triangulation sensor and a transit time sensor depends on various factors. Distance sensors based on the triangulation principle can be used to precisely determine distances in the close range (up to 1,000 mm) with an accuracy of a few tenths of a millimeter. The transit time measurement principle can be used to determine long distances (up to 10,000 mm).
| Triangulation sensors | Transit time sensors |
|---|---|
| Precise determination of distances in the close range up to 1 m | Determination of long distances up to 100 m with reflectors |
| Linearity deviation < 1 mm | Linearity deviation > 10 mm |
| Detection of very small objects or differences in distance | Resistant to interfering influences |
Laser distance sensors that work according to the triangulation principle have a blind spot. It must therefore be ensured that the switching point is set from the start of the working range so that the object is reliably detected. Sensors that operate according to the transit time principle have no blind spot.
wenglor laser distance sensors offer various electrical interfaces:
- Analog output
- Digital outputs
- Serial port
- IO-Link
- Industrial Ethernet
Accuracy always depends on the measuring principle used. High accuracy can be achieved if the measured values are highly accurate and precise. Values such as linearity deviation and reproducibility are specified here. Sensors that work according to the triangulation principle, for example, have a linearity deviation <1 mm. ToF sensors, on the other hand, have a linearity deviation >10 mm.
Accuracy is made up of precision and correctness. To achieve good accuracy, the values linearity deviation, temperature drift, switch-on drift and switching distance deviation are important.
The maximum reproducibility, also known as repetition accuracy, refers to the maximum possible switching point or measured value deviation over the entire working range for successive measurements under the same conditions.
The linearity in the data sheet indicates the maximum possible deviation from the correct distance.
Laser distance sensors triangulation can accurately measure distances in the close range of up to 1 m. ToF sensors measure distances of up to 100 m with reflectors.
Laser classes provide information on the potential hazard of the laser to humans. The common laser classes are divided into 1, 2, 2M, 3R and 3B. wenglor distance sensors only use laser classes 1 and 2.
No protective measures are required for laser classes 1 and 2, as they are harmless to the human eye.
The laser distance sensors are available in protection classes IP67/68 and IP69K. Sensors with IP67/68 degree of protection are waterproof and suitable for use in industrial environments. Sensors with IP69K degree of protection are highly durable and resistant to cleaning agents and high-pressure cleaners. They are suitable for washdown and heavy-duty applications.
Yes, there is a password function that can be used to secure access via Bluetooth. This function is available from weCon version 2.1.1.
Yes, laser distance sensors reliably measure dark, colored, light or low reflecting objects, regardless of the degree of reflection. The measurement result does not change with different surfaces.
The speed of the sensors depends on the data output used. When using digital switching outputs, the switching frequency specifies the maximum number of switching operations per second. If the analog output is used, the measuring rate indicates how many measurements are output on the analog output per second. When using the IO-Link interface, the minimum cycle time defines how quickly new measured values are output via the interface.
With laser light or laser radiation, excited light particles emit energy in the form of light. Due to this property, the light is focused so that a laser beam only has one wavelength (one color).
Light consists of different wavelengths. Each wavelength has a specific color. The wavelength of the color blue is between 380 and 500 nm.
A stainless steel protective housing is optionally available for some laser distance sensors. The protective glass can also be replaced if it becomes worn. Alternatively, for the P3 series, there is a protective film made of gorilla glass, which can be easily applied to the optic cover just like a smartphone.
Questions About Triangulation Sensors
The calibration report shows the measured characteristic curve for the linearity deviation for each sensor of the P3 series. After calibration, this characteristic curve is recorded in the production process and saved in the sensor.
The CMOS line is a light-sensitive receiving element. The light that falls from the object onto the line changes the position of the spot depending on the distance of the object. With the CMOS line, objects can be accurately detected even at short distances.
The temperature range is specified in the technical data. It ranges from min. –30 °C to max 60 °C. The CMOS sensors have a low temperature drift and therefore deliver consistently good measurement performance under fluctuating temperature conditions.
Yes, the measurement report can be generated individually for each sensor as a PDF for the P3 series sensors with the wTeach software. For PNBC sensors, the report is stored on the web server.
Questions About Time of Flight Sensors
The Time-of-Flight measuring principle measures the distance of objects using light pulses. The diode in the sensor emits laser pulses that are reflected by the object. The time from emission of the light pulse to the object and back is measured. The distance to the object is determined by the time and the speed of the light.
The speed of light is a fundamental constant of physics. In vacuum, it is 299,792,458 m/s.
No, ToF sensors allow up to six laser sensors to be installed directly next to each other and even opposite each other without influencing each other.
No, time-of-flight sensors are extremely resistant to disruptive ambient light (up to 100,000 lux) thanks to DS technology. This means that reliable function is guaranteed even in strong sunlight.
Yes, short-term disturbances such as raindrops can be effectively suppressed. The same applies to dust and sawdust.
Yes, ToF sensors are not only suitable for distance detection, but also for intensity and speed measurement.
DS technology stands for Dynamic Sensitivity technology. In contrast to conventional light runtime technologies, very short light pulses in the nanosecond range are emitted here, which are statistically evaluated to determine the distance value to the object.
Any questions?