KB036 What needs to be considered when using the orange reflective tape?
Beginning from an approximate measuring distance of 70 m to 100 m and depending on the quality of a natural surface, reflectivity decreases to such an extent that reliable distance measurement is no longer possible.
However, if a calibrated, orange Dimetix reflective target plate is used, measuring distances of up to 500 m are possible (depending on the sensor type). Moreover, a reflective target plate generally results in higher measuring speed.
In addition, the following factors should be considered:
- The selection of a D-Series sensor type with suitable measuring range through the use of “Measuring range on reflective tape” found in the specification table. Remember that not only the maximum but also the minimum measuring distance must be considered
- The reflective target plate must not be scratched during assembly, operation and maintenance
- Depending on the application, it may be necessary to periodically clean the reflective target plate. Use a soft, non-scratchy cleaning cloth and soapy water for this. Solvents must not be used
- The permissable operation temperature range is -20 to +90 °C
- To assemble of the reflective target plate, please click here
- To cover a larger area with a orange Dimetix reflective foil, please click here
KB037 How is the orange reflective foil glued?
Experience has shown that for untrained staff gluing on the orange Dimetix reflective foil is difficult and the result is often unsatisfactory. We therefore strongly recommend that this task is assigned to a specialist (e.g. a graphic artist) who is skilled in handling self-adhesive foil.
Please also note the following information:
- We recommend sticking the foil on an aluminum plate, because we have had positive results using this material. Other solid and smooth surfaces are also possible.
- The surface to which the foil is to be glued must be absolutely free of dust and grease.
- We recommend working the foil at 20 °C to 30 °C. The foil must not be worked at temperatures below 10 °C and above 40 °C.
- The surface can be moistened with a little soapy water (approximately 5 to 8 drops of soap in 500 ml of water). A spray bottle is ideal for this. Moistened in this manner, the foil can still be manipulated on the underlay minimally if necessary,
- Then use a soft plastic spatula to wipe off the air bubbles, working from the center of the surface to its edges. At the same time, soapy water between the foil and the underlay should also be removed. During this stage, special care must be taken to ensure that the foil is not scratched.
- Let the surface dry for a day or two.
In many cases, the ready-to-use orange Dimetix reflective target plate (Part.No. 500113) can be used as a simple and time-saving option.
KB025 What types of measurement are available?
Dimetix sensors support different types of measurements. Depending on the application, it is possible to choose between the following measurement types:
- Single distance measurement
- Single sensor tracking
- Tracking with buffering
Single distance measurements: (see top picture)
With the command sNg (N represent the ID of the sensor, e.g. ID 0 => s0g) a single distance measurement is triggered. The measurement result is send immediately to all output interfaces.
This process can be repeated as soon as the sensor response is received. The single distance measurement type is often used in monitoring applications.
Single sensor tracking: (see center picture)
A continuous measurement can be triggered with the command sNh. Depending on the application, it makes sense for the sensor to measure at regular intervals.
The desired sampling time can be given with the command sNh+x (x in ms, max. 24h => 85’400’000 ms). This type of measurement is used in various areas (wood industry, steel industry, monitoring, logistics etc.).
Tracking with buffering: (see bottom picture)
If several sensors are connected to a serial interface (e.g. RS-485), the data line should not be permanently occupied. With the measurement type tracking with buffering sNf (sNf+x, x in ms), the sensor can measure independently of other sensors. The measurement result is buffered in the sensor and only with the command sNq from the PLC, the sensor returns the result. This means that the data line is only used for a short time. This type of measurement is mainly used in the monitoring area with several sensors.
Further details can be found in the Technical Reference Manual (see Downloads).
KB026 What are measurement characteristics and what are their advantages?
With the measurement characteristics the laser distance sensors’ accuracy and measurement rate can be matched to your application’s requirements (see adjacent table – top image – above left).
Measurement characteristics: Normal, Fast, and Precise (see center image):
- Generally a sensor needs more time for a measurement, if a high measurement accuracy is to be achieved. (i.e a high measurement accuracy results at a lower measurement rate, and vice versa)
- These three measurement characteristics make it possible to achieve the optimal compromise between accuracy and measurement rate for the respective application.
- The table shows the measurement rates possible under optimal conditions. However, in case of dark or distant measurement targets, the sensor automatically increases the measurement time, so that the required accuracy can be achieved.
Measurement characteristics: Timed (see imagine at bottom):
- The Timed measurement characteristic is available for applications that require a constant measuring interval (e.g. with control loops).
- If conditions are not optimal (dark or distant target), measurement time is not automatically increased. Instead, the measurement result is outputted with reduced accuracy at the end of the measurement interval.
- If the measurement cannot be carried out in the required time, an error is outputted.
Measuring characteristics: Moving target:
- This measurement characteristic is optimized for continuously and rapidly moving targets.
- With the moving target characteristic, the quality of the measurement signal is crucial. Therefore the orange Dimetix reflective foil should be used whenever possible.
- Moving target works best with steadily changing distances. Sudden changes in distance are still recorded correctly, but output accuracy is temporarily reduced.
You can find more information on measurement characteristics in our Technical Reference Manual in the download section.
KB038 What do you need to consider when choosing a sensor?
In order to select the appropriate D-Series sensor for your application from the comparison table, the following questions should be clarified first.
Will the orange Dimetix reflective foil be needed?
- The orange Dimetix reflective foil must be used for distances greater than 100 m. (Caution: Reflective foils from other manufacturers can damage the Dimetix sensor).
- If a high measuring speed has to be achieved at distances of less than 100 m, an orange Dimetix reflective foil is highly recommended.
- Please note: The use of the orange Dimetix reflective foil is not possible – or only possible to a limited extent – with some of the D-Series sensors.
- For more information about measuring on natural surfaces, click here.
- For more information about measuring on the orange Dimetix reflective foil, click here.
What is the longest distance to be measured?
- Please note: In the comparison table the maximum possible measuring distances for the orange Dimetix reflective foil and for natural surfaces are listed separately.
When measuring with the orange Dimetix reflective foil, what is the shortest distance to be measured?
- If you never measure less than 40 m distance on the orange Dimetix reflective foil, you can often save considerable costs by choosing a DAN-10-150 or DAN-30-150.
- If distances less than 40 m will be measured with the orange Dimetix reflective foil, then this must be taken into account when selecting a sensor, otherwise there is a risk that the sensor can be damaged.
What accuracy of measurement is required?
- For maximum precision sensors with a measuring accuracy of ±1 mm @ 2σ are available.
- For cost optimal results consider whether or not a ±3 mm or even ±5 mm accuracy might be sufficient for your needs.
Which measuring rate is required?
- Please note: With natural surfaces, the effectively achievable measuring rate depends on both the surface and the distance.
- For more information, click here.
What is the temperature range at the location where the sensor will be used?
- For indoor applications, a temperature range of -10…+50°C is usually sufficient.
- For outdoor applications and production facilities, sensors with an extended temperature range of -40…+60°C are available.
- At temperatures outside the specified range, the sensor must be protected by suitable measures (e.g. with the air cooling jacket for the Dimetix D-Series sensors).
Will measurements be made on shiny metallic surfaces?
- Similar to the orange Dimetix reflective foil, shiny metallic surfaces may cause high signal levels – especially at close range.
- To prevent the sensor form over-amplifying, we recommend a sensor that is in the close range (0.5 m) capable of measuring on the orange Dimetix reflective foil.
- For more information about shiny surfaces, click here.
Will measurements be made on “difficult” surfaces? (e.g. dark, porous, glowing hot, or shiny surfaces)
- Difficult surfaces can impair a sensor’s measurement performance (e.g. maximum distance, measuring rates, accuracy) or even make measurement completely impossible.
- It is therefore recommended that test measurements are carried out under realistic conditions at an early project stage and to seek advice from Dimetix or our local sales partner.
KB040 Which sensor operating modes are available?
Operating mode: Controlled
In this operating mode, measurements are always triggered via one of the serial interfaces (RS-232, RS-422/485). Depending on the measurement command used, this happens either once after the power-up, or individually for each measurement.
In the first figure on the left, the command Single Sensor Tracking With Timer (sNh + 1000) is used. This command is executed once after the power-up, after which the sensor sends the measured distance every 1000 ms.
Before initial operation an optional one-time configuration of the sensor can be carried out (e.g. the serial communication parameters). The easiest and most convenient way to do this is to use the Dimetix Laser Sensor Utility software, which communicates with the sensor via RS-232 or USB.
See also Technical Reference Manual D-Series, Chapter 6.2 Operation modes and 6.2.1 Controlled mode.
Operating mode: Stand-alone / Autostart
In this operating mode, the sensor begins to measure automatically after it is switched on. Optionally the sensor can output the measured distance via the serial interfaces (RS-232, RS-422/485), as shown in the second figure on the left. However, this operating mode is particularly suitable for outputting the measured distance via the analog output AO or the SSI interface. This allows to operate the sensor entirely without serial communication.
For this operating mode, the sensor must be configured via RS-232 or USB before putting it to service e.g. with Dimetix Laser Sensor Utility software. See also Technical Reference Manual D-Series, Chapter 6.2 Operation modes and 6.2.2 Stand-alone mode.
Operating mode: Stand-alone / Manual start
In this operating mode, the sensor is controlled via the digital input DI1. Different functions are available for this, e.g. the digital input function “Trigger Distance Measurement (sNg)” as shown in In the third figure on the left.
The measured distance is output via the serial interfaces (RS-232, RS-422/485) as well as via the analog output AO or the SSI Interface.
For this operating mode, the sensor must be configured via RS-232 or USB before putting it to service e.g. with Dimetix Laser Sensor Utility Software. See also Technical Reference Manual D-Series, Chapter 6.2 Operation modes and 6.2.2 Stand-alone mode.
KB028 How can the sensor firmware be updated?
The Dimetix laser distance sensor can be updated via the USB or the RS-232 interface. The update instructions can be downloaded from the link: Firmware Update.
The necessary firmware download files must be requested via Dimetix. This ensures that no effort is made due to unnecessary updating.
KB030 How should the sensor be cleaned?
The laser distance sensors are almost maintenance-free. However, the following checklist for maintenance should be processed cyclically and reacted accordingly:
- Check sensor optics for contamination → Clean laser exit glass and receiver lens carefully if necessary (Note: Only use tools suitable for cleaning optical parts / instruments)
- Check valve diaphragm → Valve diaphragm must be free of contaminants (no water, dirt, etc. on the valve diaphragm)
- Check general sensor status → Sensor must not be damaged, must be correctly assembled and should always be clean
Note: Highly contaminated sensor optics can adversely affect the measurement performance (accuracy, speed) or lead to measurement errors.
KB042 What must be considered for outdoor applications?
Protection from rain and snow
The Dimetix sensors are IP65 protected (dust and splash water proof). Nevertheless, they should not be permanently exposed to rain or snow:
- Standing water on the valve diaphragm on the sensors back side can leak in over time.
- Water drops or standing water on the optics can interfere with the measurement.
- Dirt and dust dissolved in the rainwater are deposited on the optics.
Depending on the alignment of the sensor, the following measures are possible:
- Horizontally or vertically downwards: Protective roof above the sensor (first picture on the left).
- Vertically upwards: Glass roof above the sensor (second picture on the left). Please also note the separate article measuring through glass.
Depending on the site of operation, dust protection is also recommended:
- Dust on the sensor optics can lead to mismeasurement.
- Too frequent or inappropriate cleaning can reduce the service life of the sensor optics. Please also note the separate article cleaning the sensor.
The following realizations are possible:
- Dust-proof housing with a glass window through which measurements are taken (third picture). Please note the separate article measuring through glass. To prevent condensation, the housing should have an opening on the underside covered with a dust filter.
- Housing under slight overpressure with an open measuring window similar to the Dimetix Air-cooling jacket (fourth picture).
Direct sunlight on the optics can lead to measurement errors. If measurements are taken in the direction of the sun, the sensor optics should therefore be shaded. The following measures have proven effective:
- Roof with overhang (fifth picture). It makes sense to realize this as a combined sun and rain protection.
- A tube in front of the sensor optics can be even more effective (bottom picture). However, the tube must not mask either the laser exit lens nor the sensor entrance lens. The pipe diameter should therefore not be too small (C-Series and D-Series min. 35 mm). Ideally, the inside of the pipe should be as dark and matt as possible.
A closed housing exposed to the sun can heat up considerably and the max. operating temperature of the sensor can be exceeded. Therefore additional measures may be necessary such as:
- Light exterior color of the housing.
- Insulated housing top side.
- Doubled top side of housing with air gap.
- Actively cooled housing.
After completing the installation, be sure to check
- The sensors black or transparent plastic rear cover must close tightly.
- Tighten the sensors cable gland, so that it closes firmly.
KB045 What dose IP65 mean?
IP (Ingress Protection) ratings are defined in IEC 60529. This standard classifies and rates the degree of protection provided by mechanical and electrical enclosures against dust, accidental contact and water. It is published in the European Union by CENELEC as EN 60529.
Dimetix sensors are rated as IP65:
- Digit 6 means: Dust-tight (no ingress of dust).
- Digit 5 means: Water tight (water jet from any direction).
It is important to know that according to IP65 water-tightness is temporary and not permanent.
To ensure IP65 protection, the sensors exchangeable cover must be mounted correctly and the cable gland must be tightened firmly.
Generally the aging of materials can lead to a deterioration in tightness (e.g. brittle seals).
Protect the sensors from the effects of weather outdoors and damp environment. Please also note the separate article outdoor applications.
KB032 How can configuration files be loaded and saved with the Laser Sensor Utility?
With the Laser Sensor Utility Software from Dimetix, configurations from different devices can be loaded, saved and transferred. It is important that the latest software version is used. The software can be downloaded from the Dimetix website.
If a configuration of an older/other sensor has to be transferred to a new sensor, the following steps must be carried out.
- Connect the old/other sensor to the Laser Sensor Utility
- The current configuration of the sensor can be read out with the menu file -> Read configuration from device (see top image)
- Save the current configuration on your computer: Menu File -> Save configuration as … (see center image)
- Now the new sensor can be connected to the Laser Sensor Utility
- The configuration can be downloaded directly on the sensor: Menu File -> Download configuration to device (see bottom image)
- The new sensor is now ready for use. Note: It is possible that some measurement commands have changed slightly compared to older series (more information can be found in the Manuals).
KB041 How to find the COM port number of the Dimetix sensor?
To access the Dimetix Sensor with the Laser Sensor Utility software (or an other Software) via the RS-232 or USB Interface, the COM number of the used interface must be determined first.
The easiest way is to use the Laser Sensor Utility Software directly.
- Make sure that the sensor is not yet connected to the PC via USB
- Start the Laser Sensor Utility software.
- Expand the selection field “Communication Parameters / Ports” to show the already existing COM numbers. In the first figure on the left, this is COM1, COM2, COM11 and COM12.
- Power the sensor with an external 12-24V power supply and connect it with a USB cable to the PC.
- Click the “Refresh port” button in the software.
- Expand the selection field “Communication Parameters / Port”. An additional COM number is now displayed. In the second figure on the left, this is COM3. This is the COM port number of the sensor.
RS-232 (connected to the PC via RS-232/USB adapter):
Except that the sensor is connected via RS-232/USB adapter, the procedure is the same as for USB interface. Make sure that the RS-232/USB adapter is not connected to the PC at the beginning.
RS-232 (directly connected to RS-232 connector of the PC):
The easiest way is to try one COM number after another using the Laser Sensor Utility software.
- Power the sensor with an external 12-24V power supply and connect it to the RS-232 connector of the PC.
- Start the Laser Sensor Utility software and select the lowest COM number in the “Communication Parameters / Ports” selection field and click the “Check Connection” button. In the third figure on the left you can see that the first connection attempt using COM1 failed.
- Select one COM number after the other as described above and click “Check Connection” until the software connects successfully to the sensor. In the fourth figure on the left, this is the case with COM2. COM2 is therefore the COM port number you are looking for.
Windows Device Manager:
With the program “Device Manager”, which is standard on every Windows PC, the existing COM port numbers can also be displayed. See the figure below on the left. This allows a direct overview of the existing COM port numbers.
MB010 How to use the adjustment aidThe video shows how to use the simple adjustment aid integrated in the D-Series Sensors.
MB011 Correct mounting of exchangeable coverThe video shows how to correctly mount the exchangeable cover of the D-Series Sensors.
MB020 How to perform a resetThe video shows how to perform a reset of the D-Series Sensor.
MB030 How to install the Industrial Ethernet interfaceThe video shows how to install the Industrial Ethernet interface.
MB040 What are the basics to start sensor configurationsThe video shows the basics to start sensor configurations.
MB050 How to load and save configuration files with ”Laser Sensor Utility” softwareThe video shows how to load and save configurations files with the ”Laser Sensor Utility” software.
MB060 How to measure through glassThe video shows how to measure through glass.
MB070 How to clean laser sensor opticsThe video shows how to clean laser sensor optics.
MB080 How to configure the digital output hysteresisThe video shows how to configure the digital output hysteresis.
KB002 How is the measuring rate influenced?
The measuring rate of the sensors is influenced by different factors. Essentially the signal level of the reflected laser light has an important influence on the measuring rate. On a bright measuring surface (e.g. white) with good reflectivity, a measurement takes less time than on a dark surface (e.g. black) with low reflectivity.
The following factors can influence the measuring rate / measuring speed in a positive manner:
- Condition of the measuring surface (e.g. mat, smooth)
- No / little background light (e.g. sunlight, spotlight)
- Reduction of the measuring distances
- Configuration of the sensor
KB005 Is it possible to measure a moving target?
Dimetix sensors are able to measure on moving targets. Thereby the maximal possible object speed depends on the following factors:
- Measuring condition (light conditions, ambient light)
- Object- / Measuring surface condition
- Sensor specification measuring speed / rate (see Products)
Generally with higher measuring rates the maximal object speed will be higher as well. It is important to realize that the measured distance is averaged over the measuring time of one measurement.
KB006 What is the measuring accuracy?
The measuring accuracy of Dimetix sensors is specified with a statistical confidence level of 95.4% (corresponding to ISO 1938-2015). This is equivalent to ±2σ or two times the standard deviation σ (see the figure).
The following distance errors are considered in this measuring accuracy as well:
- Distance error due to temperature influence (Sensor temperature)
- Linear error
It is important to realize that the sensors do not compensate the humidity, the air pressure or the air temperature. If the environmental conditions differ from 60% relative humidity, 953mbar air pressure or 20°C air temperature, the accuracy can be influenced if the measuring distances are longer than 150m. The influence of these environmental conditions is described in H. Kahmen & W. Faig: “Surveying”, (1988).
KB008 What is the repeatability?
KB009 What is the difference between measuring accuracy and repeatability?
Measuring accuracy is specified with ±2σ (see measuring accuracy). This accuracy includes also distance errors due to temperature changes or linear errors.
In contrast to this, the repeatability is only valid for stable measuring conditions like same distance, identical measuring target, etc. (see repeatability).
KB021 How can the best measurement results be achieved?
The best measurement results can be achieved if the following factors are considered:
- Select suitable sensor according to the application requirenment: Accuracy, measuring distance, measuring speed, temperature range
- Optimal measuring surface: Flat, fine, light, matt (for more details, see Optimal measureing surface)
- Good measuring conditions: Reduce ambient light (e.g. shieldings, shadow, darkness, etc.), stable temperatures, clear and clean air (no dust, fog, rain, etc.)
- Select appropriate sensor configuration: Suitable measuring characteristic, longer measurement times, filter options (e.g. Moving average, error suppression), etc.
Additional information can be found in the Technical Reference Manual of the laser distance sensors or in other selected FAQ topics.
KB024 Is it posible to measure on hot or glowing surfaces?
Basically a measurement on hot or glowing surfaces is possible. This has already been implemented in numerous projects using the Dimetix sensors (see Application Example Steel). Depending on the application, additional measures may be required.
It is important to protect the sensor against extreme temperatures. The sensor should therefore be installed at an adequate distance and / or inside a cooled housing.
Hot surfaces emit light over the entire spectral range and thus also within the red wavelength of the laser (Type. 650nm). The higher the temperature is, the higher the disturbance. (See picture on the left)
The filter glass integrated in the laser sensors already reduces disturbances outside of the laser’s wavelength. In order to even further reduce disturbances, an additional bandpass filter glass can be installed in front of the sensor optics.
KB043 How can the measuring accuracy be converted?
What is the measurement accuracy of the Dimetix sensors with different σ values and what exactly does this mean?
The measurement accuracy of the Dimetix sensors is specified at ±2σ.
In the table on the left, the ±2σ accuracy specifications of the Dimetix sensors were converted into the commonly stated ±1σ and ±3σ accuracy specifications. The table also explains how this information must be understood.
It should be noted that the measurement accuracies of ±1σ, ±2σ and ±3σ always refer to the same statistical scatter, despite their different numerical values.
This can also be explained by the following example: The accuracy specifications of ±0.5 mm@1σ, ±1.0 mm@2σ and ±1.5 mm@3σ are the same, it is just expressed differently. See measurement accuracy.
How can other manufacturers accuracy specifications be compared with the Dimetix accuracy specifications?
Only a few sensor manufacturers specify the measurement accuracy at ±2σ. For a meaningful comparison, these accuracy specifications must therefore be converted.
The figure on the lower left shows the general formula to calculate the accuracy @ ±2σ from the accuracy @ ±Nσ.
The figure also shows a conversion example. At first glance, the accuracy of ±1.0 mm seems comparable to the Dimetix Dxx-10-xxx sensors (e.g. DPE-10-500). After the conversion, however, it turns out that this sensor measures two times less precise.
KB007 How can the sensors be connected to PLC systems?
Dimetix sensors offer different connection possibilities with the PLC systems available on the market.
Some of these possibilities are listed below:
- RS-422 interface: Sensor commands (ASCII-based) are exchanged between PLC and sensor via RS-422 interface (see AN2010, example with RS-422 interface and Siemens S7).
- External PROFIBUS interface: DIMS protocol converter (Dimetix Art.No. 500214) for sensor connection to an existing PROFIBUS interface (see AN2005, example with DIMS PROFIBUS and Siemens S7).
- Industrial Ethernet interfaces: Newer sensor types have optionally-integrated PROFINET, EtherNet/IP or EtherCAT interfaces (see Dimetix website for details).
Other standard integrated sensor interfaces can, of course, also be used for a connection to a PLC system. More information about the available interfaces of the Dimetix Sensors can be found on the Dimetix website.
KB012 How long can the RS-232 data cable be?
The RS-232 interface is not designed for long data cables (no differential signals). The cable length depends mainly on the data rates of the RS-232 interface.
See the following guidelines:
- 19’200 Baud → up to 15m
- 115’200 Baud → up to 2m
The cable length is also influenced positively / negatively by other factors:
- Quality of the cable (shielding, cross-section, wire resistance, etc.)
- Environmental conditions (Disturbance sources like motors, etc.)
KB013 How long can the RS-422 / RS-485 or SSI signal cable be?
RS-422 / RS-485 and SSI are differential serial data interfaces designed for long data cables. The cable length depends on the cable quality and data rates.
See the following guidelines for the RS-422 / RS-485 interfaces:
- 19’200 Baud → up to 1000m
- 115’200 Baud → up to 500m
See the following guidelines for SSI interfaces:
- ≤ 100kBit/s → up to 1000m
- ≤ 500kBit/s → up to 200m
- ≤ 1000kBit/s → up to 100m
Cable type and termination:
- Use only shielded twisted pair cables
- Termination according to characteristic impedance of the cable (typically 100 – 150 Ω)
The cable length is also influenced positively / negatively by other factors:
- Quality of the cable (shielding, cross-section, wire resistance, etc.)
- Environmental conditions (Disturbance sources like motors, etc.)
Further details in the Technical Reference Manual (see Downloads).
KB014 What must be considered regarding the connecting cables?
When selecting the sensor connection cable, the following points should be considered:
- Cable cross-section according to the maximum sensor current
- Wire resistance for long cables (Attention: voltage drop through cable)
- Cable requirements according to specifications e.g. shielded twisted pair cable for RS-422 / RS-422 or SSI interfaces, with specifications according to Technical Reference Manual (see Downloads).
KB015 When is a termination recommended for RS-422 / RS-485 or SSI interfaces?
A proper termination of the data lines is recommended in any case. However, for very short data lines and data rates up to approx. 200 kBit/s, a termination is not absolutely necessary.
The specifications of the Technical Reference Manual must be observed (see Downloads).
KB019 Where can FAQ’s for Industrial Ethernet interfaces be found?
The FAQs for the Industrial Ethernet interfaces are listed in the corresponding Technical Reference Manual (see Downloads).
KB027 How can multiple sensors be connected on a single line / cable?
Up to 100 sensors can be connected to one line via the RS-422 or RS-485 interfaces. In this case, a different ID must be configured for each of the sensors, so that all sensor can be addressed by the controller.
It is mandatory to use a twisted pair cable which is terminated with a termination resistance of 100-150 ohms.
In certain applications, it is necessary that the sensors measure permanently (tracking mode). So that the line is not blocked, the Tracking with Buffering (sNf) in the sensor must be activated for this purpose. The controller can then read the result from each sensor with the command sNq (N is replaced by the ID of the sensor).
Further details in the Technical Reference Manual under RS-422/485 interface (see Downloads).
KB001 Is the Laser Light eye-safe?
Dimetix sensors belong to Laser Class 2. Sensors of this laser class have visible laser light and a laser power pulse less than 1mW (<1mW).
It should be acknowledged that in normal cases the bright light of a Class 2 laser beam directed into the eyes will cause an instinctive reaction to look away or close the eyes. This automatic response is expected to protect you from Class 2 laser damage to the eyes.
If Class 2 laser beams are directly viewed for a prolonged period of time damage to the eyes could result. Avoid looking into a Class 2 laser beam or pointing the beam into another person’s eyes. Avoid viewing Class 2 laser beams with telescopic devices.
KB003 On what kind of targets can be measured?
All opaque targets can be measured if they do not have highly reflective surfaces. Reliable measurements on transparent targets are not possible.
KB004 Does dust influence the measuring process?
The influence of dust on distance measurements depends on the density of dust. If the main part of the laser beam is reflected by dust particles, the distance measurement will be influenced in a negative way (measurement errors). However, such conditions can only be found in extreme dusty environments, like cement silos.
KB010 What optical disturbance sources can influence the sensors?
The sensors operate in the wavelength range of 620 to 690 nm (corresponding to red light in the visible electromagnetic spectrum). This means that all optical light sources in the same color range can act as potential sources of disturbance.
Possible disturbance sources that have to be eliminated / minimized:
- Other optical sensors in the same wavelength range
- Rotary lights / flashing lights / flashlights
Possible approaches to minimizing such disturbance sources:
- Separate the sensor from other sensors of the same spectrum
- Shield sensors with housing / covers
KB011 Is it possible to measure through glass?
It is not recommended to measure through glass, since there will be signal loss and reflections on the glass may have a negative impact on the accuracy.
However, if glass is the only option for a specific application, check the following points:
- Use coated glass to reduce the reflections and signal loss
- Install the glass with an angle from the front of the sensor by a minimum of 5°
- Keep the glass clean at all times
KB016 What is the optimal measuring surface?
An optimal measurement surface has the following properties:
- Flat, fine and not porous
- Diffuse reflective (not glossy)
- Bright and stable / low vibration
- Bigger than the laser spot
Measurement can be divided into two use cases:
- Natural measurement surfaces: None / Low Influence on measurement surface.
- Selectable measuring surface:
The possible measuring range of the sensors must be checked according to the specifications (see Products).
KB017 What should be considered for glossy measuring surfaces?
Measuring on high glossy measuring surfaces should be avoided. Strong signal fluctuations and unwanted reflections can negatively influence the measurement accuracy, cause measuring errors or possibly damage the sensor.
If high glossy measurement surfaces are unavoidable, the following recommendations should be considered:
- Do not measure perpendicular to the glossy measuring surface
- Use optical filter / attenuation (before sensor optics) for signal attenuation
KB018 How can optical sources of interference be minimized?
Dimetix sensors have an integrated filter glass to keep the influence of possible optical sources of interference small. This band-pass filter has the task of letting pass only the signal in the wavelength range of the laser (typically 650nm).
Nevertheless, especially for applications with very strong optical interference sources, an additional filter or shielding can significantly improve the measurement performance.
The following measures can help:
- Mount an additional bandpass filter in front of the sensor optics.
Note: Do not mount the filter perpendicular to the laser beam (See Measuring through glass)
Filter properties: Bandpass filter with CWL: 650nm and FWHM: ~30 to 40 nm (±15 to 20 nm)
- Use shielding to protect the sensor optics from optical interference sources. (Example: Screening plate, pipe in front of the sensor optics)
Attention: The laser output as well as the receiving lens of the sensor must be free and must not be covered.
KB020 How should the orange reflective target plate be mounted?
When assembling the orange reflective target plate or reflective foil, the following points must be observed for trouble-free operation:
- Only use the Dimetix reflective target plate (See accessories)
- Mount the reflective target plate at an angle of 1-2 ° (see figure)
- Do not scratch the reflective target plate
- Scatter light must not be reflected in sensor optics
- The entire laser spot must fit on the reflective target plate (spot size depending on the measuring distance)
- For targets with a large horizontal / vertical offset or alignment tolerance (e.g. crane systems), use sufficiently large reflective foil.
KB022 What is the size of the laser spot?
The laser is located with 650 nm in the region of the red spectrum. The laser spot typically becomes larger as a function of the increase in the measuring distance. The laser spot has the shape of an ellipse.
Further details are available in the Technical Reference Manual under specifications (See Downloads).
KB023 How is the reflection factor defined?
The reflection factor is defined by the ratio of the remitted luminiance of a surface in the direction of measurement to the luminosity of a surface in reference white. As reference white an ideal white and matt surface is used.
The figure shows some reference values with different measurement characteristics versus distance. From these values, the appropriate target for the desired measurement distance can then be determined.
KB031 What should be considered when measuring with several laser sensors?
When measuring with more than one sensor, the sensors should be placed and aligned so that they do not interfere with each other. The receiving optics of the sensors have a conical field of view. Everything outside of this field of view is not visible to the sensor and is therefore not disturbing.
Parallel measurement in the same direction:
This scenario is shown in the above figure on the left. The spacing s between the two laser beams must be chosen so that the laser beam of one sensor does not hit the target within the field of view of the other sensor.
In practice, the following formula applies for the minimum spacing s:
smin = 0.1 m + d [m] * 0.004
Parallel measurement in the opposite direction:
This scenario is shown in the second figure on the left. The distance between the two laser beams must be chosen so that the laser exit point of one sensor is outside the field of view of the other sensor. The same formula as above can therefore be applied.
To avoid damaging the sensors, make sure during alignment that the laser beam is not directed directly at the receiving optics of the opposite sensor.
The table on the left shows the permitted minimum distances smin for a set of measuring distances d.
KB033 How can the laser point be best aligned?
Process of laser point alignment (especially for positioning applications):
- Alignment at close range (about 5 cm): Align the sensor to the center of the measurement target (horizontally and vertically). Attention: Adjust the position of the sensor / measuring target only in this step. In the following steps only to fine adjustment of the sensor.
- Alignment first distance (about 10 m): Re-adjust the laser point to the center of the measurement target. Use the alignment screws of the sensor or the alignment possibilities of the sensor mounting.
- Alignment further/larger distance (about 20 / 50 / 100 m): Re-adjust the laser point to the center of the measurement target. Use the alignment screws of the sensor or the alignment possibilities of the sensor mounting.
Note: Typically, alignment is relatively good from about 50 m.
- Check alignment: Check if the laser spot is on the measurement target for the entire measurement range. If it is not, restart from step 2.
Note: To view the film sequence for alignment with Dimetix Sensors, see Dimetix Youtube.