Welotec Owlf series User manual

User Manual

Laser Distance Sensor

User Manual

Laser Distance Sensor

OWLF series

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Contents 3snoitcurtsniytefaS.1

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10. Connection diagram and pin assignment 40

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1 Safety instruction

Laser safety

•The laser diode installed in the OWLF emits visible red laser lights. This

laser belongs to the Class 2 laser standard specified by the IEC 60825-1

/ 2001. It also complies with 21 CFR 1040.10 and 1040.11 except for

deviation pursuant to laser notice No. 50, July 2001.

•Max. average output power < 1 mW

•Laser radiation, do not stare into beam

•To avoid uncontrolled laser exposure we recommended stopping the

beam with a matte object.

•For laser safety reasons, the voltage supply of the sensors must

be turned off when the whole system or the machine is turned off.

•Safety concept information and limiting parameters as published in

the sales documentation apply at all times.

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2 Introduction

The latest generation of laser distance sensors are setting new standards in terms of speed and

performance. The short response time (300…900µs) makes it possible to measure small and fast

moving objects up to 600 mm away and 0.3...2.7ms up to 1000 mm away. The advanced teach-in

function allows arbitrarily configuring the measuring range between the default limits in order to

increase the resolution. This allows the complete output swing of 4 – 20 mA and 0 – 10 V to be

mapped on the new range.

The alarm output switches on as soon as the sensor receives no usable signal or as soon as the

object is outside the measuring range.

The sync. output allows the sensor to synchronize the measurement or to use several sensors in a

non-synchronous mode when they would normally interfere optically or to synchronize sensors to a

machine clock or pulse.

The distance measurement is based on the triangulation principal. The use of a photodiode array as

the receiver and the intelligence of a high performance microcontroller produce measuring results

that are almost independent of object colors and just a very small linearity error in the analog output

signal.

The rugged sensor has a metal housing with a front cover made of glass. The 90° rotating connecter

allows wiring the sensor from the bottom or the rear .

Welotec GmbH

Zum Hagenbach 7 D-48366 Laer

www.welotec.com info@welotec.com

Fon: +49 (0)2554/9130-00 Fax: +49 (0)2554/9130-10

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3 Functional principle

The distance measured is based on the triangulation principle. The emitted laser beam falls on the

object as a small light spot and will be reflected diffusely. The position of the received light spot on

the receiver (a diode line) defines the receiving angle. This angle corresponds to the distance and is

the base for the internal calculations.

A distance change close to the sensor effects a large change in angle; the same distance change at

the end of the measuring range has a much smaller effect to the angle. This non-linearity feature is

linearized by the microcontroller. The analog output signal is linear to the distance.

The sensor adapts automaticallyto different object colors by varying the emitting laser intensity and

optimizing the exposure time. The result is a sensor that is nearly independent on different reflections

(different colors, shiny surfaces, dark objects). The sensor reaches its highest accuracy if the object

reflects diffusely.

Diode line with

receiving light spot

Object far away

Object closeto sensor

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4 Mounting instructions

•For a proper mounting, the mounting surface has to be flat. Be aware of the max. tightening

torque.

•In case of EMC, the sensor has to be grounded and a shielded cable has to be used.

•The 90° rotating connecter allows wiring the sensor from the bottom side or from the rear.

•The max. accuracy will be reached >15 minutes after power on.

Steps / edges:

When measuring right next to steps / edges, it is important that the receiving beam is not covered by

the steps / edges. This also appliesto depth measurements of holes or valleys.

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Mounting above shiny surfaces:

On shiny surfaces, it is important that no direct reflection can get to the receiving optics. The reflec-

tion could blind the sensor and produce poor results. To prevent this, the sensor may be slightly

tilted.

The direct reflection can be seen on a white piece of paper when held in front of the receiver.

Mounting above round, shiny surfaces:

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Objects with color edges in the same direction:

When color edges are orientated in the right direction, the effect to the measuring result will be minor.

If the color edges are in the wrong direction,the effect will depend on the reflectivity of the different

colors.

Shiny objects with a constant structure

Especially shiny objects with a constant structure (lathed or scuffed objects, extruded aluminum

profiles, etc.) could have a negative effect on the measuring result.

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Profile measurement:

For profile measurements, the sensor axes should be perpendicular to the moving direction.

Ambient light:

Be careful that no strong light source faces the receiving field.

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Several sensors without mutual opticalinterferences:

Several sensors, when mounted next to the other, can affect each other.When mounting a sensor,

be aware that no laser spotfrom another sensor is in the receiving field.

When mounted side by side (as shown in the picture in the middle), sensing distances up to 600 mm

can be achieved..

If it is not possible to mount the sensors the correct way, use the sync input and choose the asyn-

chronous function.

Measuring range

mutual optical

interfe

ences

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5 Application hints

To reach the maximum accuracy of OWLFxxx series laser distance sensors, keep an eye

on the following points:

Measuring on rough surfaces

All laser distance sensors are adjusted and linearized on a reference object. The object is a white

ceramic sheet with an absolutely flat surface. Many objects have a surface structure that is within the

resolution of the sensor or rougher. In such a case, the sensor with its small laser spot measures the

distance including the structure in contrastto a slide gauge that measures an average. For such

applications, we recommend to use a laser distance sensor with a laser line (OWLF 4xxx S1 L).

distance

max. min.

OWLF

Slide gauge

Flat surface

Rough surface !

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What can you do if you have color edges?

For a high accuracy measurement, it is necessary that the laser spot reflects constantly and diffusely.

Frequently, the object surface has different colors (black-white transition) or parts with different

reflectivity (marble plate).

If the laser spot falls just on a changing contrast (color edge), half of the spot will be reflected well

and the other part not so well. This produces a signal on the receiver that can not be analyzed

perfectly and causes a measuring fault.

Whole spot reflected with the

same reflectivity

accurate measurement

Spot on a color edge

measuring fault

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Often objects have several color edges on the surface.

for example:

In the field, you have no guarantee that the spot is not falling on just a color edge that can cause a

measuring fault.

Also, when the object moves, you may get an incorrect signal for each color edge (it appears that the

signal is unstable or has spikes)

In such cases, we suggest to move the object (or sensor), take several measurment values and

calculate the average. The quantity of measurment values depends on the structure, the moving

speed and the accuracy you desire.

Other possible solutions:

use a sensor with the laser line (OWLFxxxxS1 L)

contact Welotec

grooves

text

pictures !marble

rust

Measure

with

Laser Sensors

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What can you do if you have transparent, semi-transparent and highly reflective objects?

The measuring principle desires an object that reflects the light diffusely. Semi-transparent, transpar-

ent and highly reflective objects do not have this feature.

•When measuring on semi-transparent objects, the light enters the object and so the measured

distance is larger than the actual distance is.

•Light will pass through a transparent object so a measuring signal is not available.

•A highly reflective object only has a direct reflection and it is not possible to work with it. For such

an application, ask Welotec.

to measure these objects, it is only possible if you place a diffuse reflecting surface on the object

(sticker, etc.)

Semi transparent objects:

the light enters the object. the

measured distance is larger than the

real distance

Transparent objects:

The light passes the object

without a diff

use reflection.

No measurment is possible

Highly reflective objects:

Only direct reflection

No measurmentis possible

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6 Teaching the OWLF

Every sensor is delivered with the factory setup (max. measuring range). The teach-in feature was

designed to choose a smaller range within the nominal measuring range for optimizing the resolution

and linearity. Output current, voltage and alarm output adapt to the new range. Two positions must

be taught.

•The first teach-in position aligns with 0 V (or 4 mA), the second position aligns with 10 V (or 20

mA)

•These teach-in positions are always just at the border of the new range (inside the measuring

range)

•The sensor may be taught more than 10,000 times in its lifetime

•The sensor can always be reset to the factory settings

•The sensor may be taught with the teach button or via the external teach input

•During the teach-in process, the red LED and the alarm output provides a feedback

•The red LED on the back side of the sensor andthe alarm output indicate “run” mode if an ob-

ject is within the measuring range.

Attention:

Within 5 minutes after power on, the sensor can be taught via the button or the teach-in wire. After 5

minutes, the teach-in button will be locked preventing accidental adjustment. The teach-in wire is

active all the time.

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Example of a

taught measuring

range:

Example of a

reverse taught

measuring range:

m m 031m m 0 3

0V / 4mA

Analog out

10V / 20 mA

Example

of a taught

output

curve

Alarm out

LED

Standard output

curve

m m 031m m 0 3

0V / 4mA

Analog out

10V / 20mA

Example of

a reversed

output

curve

Alarm out

LED

Standard output

curve

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