Beginning from about 70 to 100m measuring distance and depending on the quality of a natural surface, the 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 500m are possible (depending on sensor type). More over, a reflective target plate generally causes a higher measuring speed.

In addition, the following should be considered:

• Selection of a D-series sensor type with suitable measuring range by the means of line “Measuring range on reflective tape” in the specification table. Not only the maximum but also the minimum measuring distance has to be considered
• The reflection target plate must not be scratched during assembly, operation and maintenance
• Depending on the application conditions, 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 permitted operation temperature range is -20 to +90 °C
• For the assembly of the reflection target plate see here
• For covering a larger area with the orange Dimetix reflective foil see here

Experience shows that for untrained staff gluing on the orange Dimetix reflective foil is difficult and the result is often not satisfying. We therefore strongly recommend that you assign this task 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 good experiences with this material. But 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 below 10 °C and above 40 °C.
• The surface can be moistened with a little soapy water (approx. 5-8 drops of soap in 500 ml of water). A spray bottle is handy for this. Like this the foil can still be moved on the underlay for a little if necessary,
• Then use a soft plastic spatula to wipe out the air bubbles working from the center to the edge. At the same time the soapy water between the foil and the underlay is also wiped out. During this step, special care must be taken to ensure that the foil is not scratched.
• Let it 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.

The 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 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 in the Technical Reference Manual (see Downloads).

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.

The laser distance sensors are almost maintenance-free. However, the following checklist for maintenance should be processed cyclically and reacted accordingly:

1. Check sensor optics for contamination → Clean laser exit glas and receiver lens carefully if necessary (only use tools suitable for cleaning optical parts / instruments)
2. Check valve diaphragm → Valve diaphragm must be free (no water, dirt, etc. on the valve diaphragm)
3. 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.

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 free of charge 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.

1. Connect the old/other sensor to the Laser Sensor Utility
2. The current configuration of the sensor can be read out with the menu File -> Read configuration from device (see top image)
3. Save the current configuration on your computer: Menu File -> Save configuration as … (see middle image)
4. Now the new sensor can be connected to the Laser Sensor Utility
5. The configuration can be downloaded directly on the sensor: Menu File -> Download configuration to device (see bottom image)
6. The new sensor is now ready for use. Remark: It is possible that some measurement commands have changed slightly compared to older Series (more information can be found in the manuals).

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 (eg. 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

The 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. Realize that the measured distance is averaged over the measuring time of one measurement.

The measuring accuracy of the Dimetix sensors is specified with a statistical confidential level of 95.4% (corresponds to ISO 1938-2015). This is equivalent to ±2σ or 2 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)
• Linearity error

Realize that the sensors do not compensate the humidity, the air pressure or the air temperature. If the environment conditions differ from 60% relative humidity, 953mbar air pressure or 20°C air temperature, the accuracy can be influenced if the measuring distances is longer than 150m. The influence of these environment conditions is described in H. Kahmen & W. Faig: “Surveying”, (1988).

The repeatability is achieved by repeatedly approaching the same distance under the same measurement conditions during a short time interval.
For example, stable measurement conditions include:

• Same distance
• Identical measurement target
• Same temperature conditions

The measuring accuracy is specified with ±2σ (see Measuring accuracy). This accuracy includes also distance errors due to temperature changes or linearity errors.
In contrast to this, the repeatability is only valid for stable measuring conditions like same distance, identical measuring target, etc. (see Repeatability).

The best measurement results can be achieved if the following topics are considered:

• Select suitable sensor according 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.

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 over temperature. 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 is also this disturbance. (See picture on the left)

The filter glass integrated in the laser sensors already reduces disturbances outside of the lasers wavelength. In order to even further reduce disturbances, an additional bandpass filter glass can be installed in front of the sensor optics.

For the alignment and selection of the filter glass, follow the instructions Measuring through glass and Minimizing optical disturbances.

The 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.

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.)

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 shielded twisted pair cables only
• Termination according to characteristic impedance of the cable (typ. 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).

When selecting the sensor connection cable, the following points should be considered:

1. Cable cross-section according to max. sensor current
2. Consider wire resistance for long cables (Attention voltage drop through cable)
3. Consider cable requirements according to specifications e.g. Shielded twisted pair cable for RS-422 / RS-422 or SSI interfaces. Specifications according to Technical Reference Manual (see Downloads).

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).

The FAQs for the Industrial Ethernet interfaces are listed in the corresponding Technical Reference Manual (see Downloads).

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 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).

The Dimetix sensors belong to laser class 2. Sensors of this laser class have visible laser light and a laser power less than 1mW (<1mW).

Realize that in normal case the bright light of a class II laser beam into your eyes will cause a normal reaction to look away or close the eyes. This response is expected to protect you from Class II Laser damage to the eyes.

If class II laser beams are directly viewed for a long period of time damage to the eyes could result. Avoid looking into a class II laser beam or pointing into another person’s eyes. Avoid viewing class II laser beams with telescopic devices.

All opaque targets can be measured if they do not have highly reflective surfaces. Reliable measurements on transparent targets are not possible.

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 particle, 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.

The sensors operate in the wavelength range of 620 … 690nm (corresponds 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
• Sunlight

Possible approaches to minimizing such disturbance sources:

• Separate sensor from other sensors in the same spectrum
• Shield sensors with housing / covers

It is not recommended to measure through glass, since there is a signal lost and reflections on the glass may have a negative impact on the accuracy.

However, if a glass is the only option for a specific application, check the following points:

• Use coated glass to reduce the reflections and signal losses
• Install the glass with an angle to the front of the sensor of 5° min.
• Keep the glass clean all the time

An optimal measurement surface has the following properties:

• Flat, fine and not porous
• Diffuse reflective (not glossy / reflective)
• Bright and stable / low vibration
• Bigger than the laser spot

The topic can be divided into two use cases:

1. Natural measurement surfaces: None / Low Influence on Measurement Surface.
2. Selectable measuring surface:
   • Short ranges → White-matt surface (E.g. white matt sprayed board as an economical solution), or Dimetix orange reflective target for more performance (see Accessory)
   • Wide ranges → Dimetix orange reflective target (see Accessory)

The possible measuring range of the sensors must be checked according to the specifications (see Products).

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

The Dimetix sensors have an integrated filter glass to keep the influence of possible optical sources of interference small. This so-called band-pass filter has the task to let 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…40nm (±15…20nm)
• 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.

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.

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 in the Technical Reference Manual under specifications (see Downloads).

The reflectance 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 surfacse 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.

Process laser point alignment (Especially for positioning applications):

1. Alignment at close range (about 5cm): Align the sensor to the center of the measurement target (horizontal and vertical). Attention: Adjust the position of the sensor / measuring target only in this step. In the following steps only fine adjustment of the sensor.
2. Alignment first distance (about 10m): Readjust 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.
3. Alignment further larger distances (about 20 / 50 / 100m): Readjust 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 50m.
4. Check alignment: Check if the laser spot is on the measurement target for the entire measurement range. If not, restart with step 2.

Note: Film sequence for alignment with Dimetix Sensor, see Dimetix Youtube Channel.