POLARIS 10 400 hw inst oper manual MAN 1104 rev 2 6 en GB

1.4 Intended use POLARIS laser sensors are used to measure the distance or the thickness of standing or moving objects.. 2.4.2 Safety instructions for Laser Class 3R These are lasers th

Please read and observe!

Keep this manual for future reference

Translation of the original

All brand names and product names are trademarks or registered trademarks of the respective title holder

© LAP GmbH Laser Applikationen,1999

The reproduction, distribution and utilisation of this document as well

as the communication of its contents to others without express authorisation are prohibited Offenders will be held liable for the payment of damages All rights reserved in the event of the grant of a patent, utility model or design

This document is intended to be used by the owner of the LAP product, its users and contractual partners of LAP It must not be handed to other persons or made available to third parties

This document is subject to a document content service and subject to change without prior notice

LAP GmbH can assume no liability for the correctness, completeness

or up-to-dateness of any laws, regulations or guidelines (e.g DIN, VDE, ) referenced directly or indirectly or quotes taken from such sources in this publication We recommend that the complete regulation or guideline in the latest valid version be consulted for work

to be carried out, where applicable

Subject to technical changes

This product complies with European statutory regulations and the requirements of the European directives These directives are listed in the accompanying EC declaration of conformity

Table of contents

1 General information 5

1.1 About this document 5

1.2 Validity 6

1.3 Styles and conventions 7

1.3.1 Safety instructions 7

1.3.2 Warning and information symbols 8

1.3.3 Markups 8

1.4 Intended use 9

2 Safety instructions 10

2.1 General safety instructions 10

2.2 Safety instructions on the mechanical system 11

2.3 Safety instructions on electrical equipment 11

2.4 Safety instructions on lasers 11

2.4.1 Safety instructions on Laser Class 2 12

2.4.2 Safety instructions for Laser Class 3R 12

2.4.3 Safety instructions for Laser Class 3B 13

2.5 Notes on the EMC Directive 14

2.6 Employer's liability insurance association regulations 15

2.7 Underlying regulations 15

3 Goods receipt, transport, storage 16

3.1 Goods receipt 16

3.2 Transport 16

3.3 Storage 17

3.3.1 Devices 17

3.3.2 Data medium 18

4 Technical description 19

4.1 The laser system in use 19

4.1.1 Operating principle 19

4.1.2 Thickness measurement using two laser sensors 21

4.1.3 Converting the sensor value to a measured value 22

4.1.4 Dimensions 23

4.1.5 Technical data 24

4.1.6 Model overview 25

4.2 Outputs 25

4.2.1 Description of the outputs 25

4.2.2 Data output format 26

4.2.3 Cable/Connector pin assignment 27

4.2.4 Function of LEDs 28

4.3 Operating modes 29

4.3.1 Single mode 29

4.3.2 Master-slave mode 29

4.3.3 Multiplex mode 30

5 Installation 31

5.1 General information 31

5.2 Cabling 31

6 Initial start-up 33

6.1 Use of the diagnostic and parametrisation tool 33

6.1.1 Scaling the measured values 33

7 Adjustment and calibration 35

7.1 Laser sensor holder of the laser system 35

7.1.1 View and structure 35

7.1.2 Operating principle 36

8 Operation 37

9 Care and maintenance 38

9.1 Care and maintenance of the system 38

9.2 Care and maintenance of the windows 38

9.3 Maintenance by LAP 38

10 Troubleshooting 40

10.1 Remedying of faults 41

11 Repair 42

12 Packaging/intermediate storage 43

13 Dismounting/disposal 44

14 Optional accessories 45

14.1 Parametrisation set of the laser system 45

14.1.1 DP-SOFT 45

14.1.2 Power supply unit for the laser sensor 45

14.1.3 RS485-USB converter 45

14.2 Interface modules 45

Annex A: Labelling of the POLARIS laser sensors 46

Annex B: Declaration of conformity 47

Annex C: Return sheet 49

Annex D: Addresses 51

Annex E: Glossary 52

List of figures 57

Index .58

1 General information

Dear customer, This document is designed to help you put your new LAP product to the best possible use By observing the infor-mation in this document you can avoid potential dangers and extend your product's service life

The product has been designed and constructed ing to the state of the art, and prior to delivery it has been checked thoroughly for proper functionality It may be used only as intended Improper use of the system will termi-nate all warranty claims The owner alone is responsible for the risk and any damage or injury

accord-This document is a component of the product Keep the document in a designated location close to the product for easy reference If the equipment is moved to a different operating location make sure the document is transferred

This document is intended for use by persons with the lowing knowledge:

fol-• Qualified technician, mechatronics engineer or similar qualification

• Instruction in laser technology

If you do not have the requisite knowledge, you should ask qualified persons or persons who have received appropri-ate instruction for assistance

The most important terms used in this document are plained in the glossary

ex-To effectively use the device, refer to the accompanying software and the functional description of the DP-SOFT

diagnostic and parametrisation tool, hereinafter tic and parametrisation tool"

"diagnos-Ensure that the version of the parametrisation tool is

at least equal to or higher than the firmware version of the laser sensor used

The version number is defined as follows:

Example:

2.3.1.26

Firmware version (see laser sensor documentation)

2 = mechanics revision, 3 = electronics revision

If you have advanced questions about the content of this operation manual or handling of the device, please contact your dealer or the regional partner of LAP The addresses and contact data of the regional LAP partners are listed in the annex

Possible modifications to this product made by users are not subject to the manufacturer's control Therefore, al-ways check whether the information in this documentation matches the actual product technology before operating or using the device In case of deviations or unclear issues, please contact us immediately This is in your own interest

docu-techdoc@lap-laser.com

This document is valid for:

• POLARIS Laser sensor 10 400

1.3 Styles and conventions

This chapter describes conventions as used in this tion manual Read this chapter to make it easier for you to use this operation manual

opera-1.3.1 Safety instructions

This operation manual uses a multi-level system to notify the reader of different degrees of hazards

DANGER Cause of the danger

Signals that death or severe physical harm will result if the specified precautions are not observed

WARNING Cause of the danger

Signals that death or severe physical harm may result if

the specified precautions are not observed

CAUTION Cause of the danger

Signals, that minor physical injury may result if the

specified precautions are not observed

Notice

Signals that property damage can occur or indicates

im-portant information on handling the product or imim-portant

sections of the document

1.3.2 Warning and information symbols

In addition to the general danger symbols, we also use the following pictograms in this operation manual in order to point out specific hazards

DANGER Electric voltage

Signals danger to life or limb with permanent physical damage due to electric voltage

WARNING Laser beams

Signals physical harm with permanent physical damage due to laser beams

Please also note the following information symbols:

Manufacturer

Fragile, handle with care!

Serial number of the devices

Keep dry!

Do not dispose of the device with regular domestic waste

We offer a return service

Please refer to the return sheet in the annex

1 Numbered list Operating steps which need to be

performed in the order listed

Tab 1-1: Markups

1.4 Intended use

POLARIS laser sensors are used to measure the distance

or the thickness of standing or moving objects They can

be installed permanently in or on a machine or building structures directly using the bracket provided

Any other use is not permitted The owner bears sole sponsibility for the consequences of improper use

Intended use also includes adhering to our instructions garding installation, removal, commissioning, operation, maintenance and disposal of the system

re-The operating staff must immediately notify the owner or his/her representative of any safety-relevant changes to the system

As a basic rule, any intended changes to the device must

be approved in writing by LAP

2 Safety instructions

2.1 General safety instructions

Safety instructions are intended to ensure occupational health and safety and the prevention of accidents They must be heeded

In order to protect you and your colleagues against injury,

we need your co-operation, too Therefore be careful at work all the times Always be aware that dangers are usu-ally "not obvious"

In order to ensure safe operation, the owner must make sure that the persons working on or with the device are in-formed about the possible dangers of laser radiation

Only qualified authorised personnel who have received appropriate instruction may work with/on the laser system described in this manual

The person who operates this laser system must have read and understood the relevant sections of the operation manual

A copy of this operation manual must always be kept in a designated location close to where the laser system is used

Safety-relevant changes to the laser system must be ported immediately to the persons responsible

The user must make sure that unauthorised persons main outside the work area of the laser system

re-Users, fitters and maintenance technicians must be given instruction on all safety-relevant aspects of the laser sys-tem by the owner on a regular basis The same applies to safety regulations that are to be observed at the user's premises and are not included in this operation manual The applicable national and local safety regulations as well as the safety regulations of the user must be strictly observed when operating or making interventions in the system

If a malfunction occurs, the laser beam may stray outside the designated zone

Use only accessories approved by LAP

Steps have been taken at the development stage to sure maximum protection of the user through the design of the laser and integrated safety devices However, this does not relieve the user of the obligation to observe his/her general duty of care

Notice

In the event of malfunctions, the equipment is to be switched off immediately and the owner or his/her repre-sentative are to be informed

The device contains highly sensitive components fore, under no circumstances should you attempt to repair

There-it yourself

2.2 Safety instructions on the mechanical system

Only use the mounting bracket provided Do not drill into the components If the installation is carried out incorrectly this could impair the measurement accuracy and damage the device In the worst case the device could come loose and cause injury

2.3 Safety instructions on electrical equipment

In the event of malfunctions in the electrical supply, the device is to be switched off immediately

Works on the device's electric system may be carried out only by a skilled electrician

Notice

The laser contains highly sensitive parts Therefore, under

no circumstances should you attempt to repair the laser yourself

2.4 Safety instructions on lasers

WARNING Potential danger of exposure to radiation

Use of operating or adjusting equipment or performance of procedures other than those specified in this document may result in hazardous radiation exposure

• Never use a different procedure than the ones scribed in this document

de-If you cannot guarantee compliance with the above, you must not carry out the work described in this document Get in touch with LAP to make corresponding arrange-ments contact information on p 51

According to DIN EN 60825-1, lasers are classified into classes 1, 1M, 2, 2M, 3R, 3B and 4

Laser class of product (depending on version):

• 2

• 3R

• 3B The laser class is shown on the laser warning label of the device

2.4.1 Safety instructions on Laser Class 2

Fig 2-1: Laser warning sign class 2 (example)

con-to the visible spectral range

• Never look directly into the laser beam

• Close your eyes immediately and turn away if the beam strikes your eye

• Prevent specular reflections

• Never point the laser beam at people's faces

2.4.2 Safety instructions for Laser Class 3R

These are lasers that deliver a medium power output

Fig 2-2: Laser warning sign class 3R (example)

• Never look directly into the laser beam

• Close your eyes immediately and turn away if the beam strikes your eye

• Prevent specular reflections

• Never point the laser beam at people's faces

• Never look into the laser beam with optical ments (e.g magnifying glasses)

instru-• Limit the laser beam to the necessary work area

• Train operating and maintenance staff in the handling

of lasers

2.4.3 Safety instructions for Laser Class 3B

These are lasers that deliver a medium power output

Fig 2-3: Laser warning sign class 3B (example)

WARNING!

Risk of injury due to exposure to the laser beam of class 3B lasers

The eyes will be injured due to exposure to the laser beam

of class 3B lasers Diffuse scattered radiation can be sidered harmless providing the observation distance is not less than 13 cm and the observation time is not more than

con-10 s

• Wear laser safety glasses while working at the laser and in the laser area

• Never look directly into the laser beam

• Close your eyes immediately and turn away if the beam strikes your eye

• Prevent specular reflections

• Never point the laser beam at people's faces

• Never look into the laser beam with optical ments (e.g magnifying glasses)

instru-• Limit the laser beam to the necessary work area

• Train operating and maintenance staff in the handling

of lasers

• Mark the laser work area using the laser warning sign

• Prevent unauthorised persons from entering rooms where the open-beam laser is operated Identify the rooms with “No Access” signs

• Ensure that operation of the laser is displayed via a visual warning that can be seen from a distance

• Secure lasers against unauthorised access using a lockable master switch, for example, using a key-operated switch

National requirements

In addition to the requirements of EN 60825-1:2007, the respective national occupational safety and health re-quirements for lasers must be reviewed and implemented

The product has been developed and tested on the basis

of Directive 2004/108/EC Make sure that the product is installed in accordance with the installation manual and in compliance with EMC guidelines Our product complies

with the limits specified in this standard for

electromagnet-ic disturbance and immunity Disturbances of other develectromagnet-ic-

devic-es are thus not to be expected However, other devicdevic-es in the vicinity may not comply with these limits and might therefore interfere with our product This particularly ap-plies to mobile radio communication devices This could lead to malfunctions Therefore ensure that all devices lo-cated in the operating area comply with the legal limits Make sure that the devices are marked with the CE label and that they have a valid declaration of conformity

If our product does not behave as described in the tion manual, switch it off immediately and inform the owner

opera-or the person acting on his behalf Under no

circumstanc-es should you try to remedy the malfunction yourself Do not modify the product

2.6 Employer's liability insurance association regulations

If you are using the device within the jurisdiction of the Federal Republic of Germany, you must observe the fol-lowing "Berufsgenossenschaftlichen Vorschriften" (regula-tions issued by the Employer's Liability Insurance Associa-tion):

• BGV A3 "Elektrische Anlagen und Betriebsmittel"

• BGV A8 "Sicherheits- und zeichnung am Arbeitsplatz"

Gesundheitsschutzkenn-• BGV B2 "Laserstrahlung"

• Production processes: DIN EN ISO 9001

• Laser safety: DIN EN 60825-1

• Electrical safety: DIN EN 61010-1

• EMC: DIN EN 61326-1

3 Goods receipt, transport, storage

Make sure that:

• The type and serial numbers on the type plates of the products match the information on the order and de-livery papers, (see Annex A: on page 46)

• The delivery is complete (compare with the delivery note)

• All parts are in a proper condition and undamaged

Notice

Notify LAP immediately in writing about any transport damage and/or missing parts and include your address and the order number

Following the incoming goods inspection, store the ponents in their transport packaging until they are in-stalled Observe the storage conditions specified in chap-ter 3.3 on page 17

com-During transportation, the products are protected against moisture by a plastic film Do not remove the film until the temperature of the products has adjusted to room temper-ature This prevents the condensation of water on or in the product When in doubt, wait for 24 hours before unpack-ing

Retain the packaging in case it is necessary to transport the equipment at a later date Dispose of the packaging if necessary in accordance with the local regulations

CAUTION

The components contain highly sensitive parts which must

be particularly protected against shock during transport/shipping

If you need to ship components, use the original LAP packaging if possible

Transport the laser sensors carefully to avoid damage due

to collisions The laser devices contain sensitive glass components

ag-Please note:

• Humidity and aggressive gases can cause corrosion

• Electronic components, motors, bearings and seals may be damaged if subjected to excessive tempera-ture fluctuations

When putting the equipment into storage, protect open plug connections from dust and moisture

The following climatic conditions must be satisfied when putting the equipment into storage:

Storage conditions

Ambient temperature 0 °C to +80 °C

Humidity 35% to 85% rel humidity,

non-condensing

Tab 3-1: Hardware storage conditions

Light irradiation No direct sunlight

Tab 3-2: Storage conditions data medium

4 Technical description

POLARIS laser sensors are used to measure the distance

or the thickness of standing or moving objects By using this measurement system, you can monitor your produc-tion completely and document the quality of the product for the customer with production logs

The laser sensors are suitable for industrial applications They can be used in any production situation to test indi-vidual parts in the laboratory and for online production control Impacts to the devices and scratches on the pro-tective glass panels could impair the functionality of the devices and must be avoided

The laser sensors operate with a max sampling rate of 4 kHz Both digital and analog measurements are output For diagnostic purposes, a video signal can be evaluated using the diagnostic and parametrisation tool

Several lasers can be operated at one RS485 interface The laser sensor parameters can also be checked and modified via this RS485 interface For this operating mode, however, each sensor must first be assigned a ded-icated address The diagnostic and parametrisation tool is used for this purpose

Some of the accessories offered by LAP:

• Laser sensor holder (see chapter 7.1) for installing and removing the POLARIS laser sensors easily

• RS485 / USB converter for connecting the POLARIS laser sensors to a USB interface

• Interface modules (see chapter 14.2) for processing binary and analog signals as well as for connecting encoders to the RS485 network

• User software for processing measurements and ualizing several laser sensors

vis-• Complete, customer-specific solutions

4.1.1 Operating principle

The measuring principle of the POLARIS laser sensors is based on the laser triangulation principle A laser beam generates a point of light on the measured object which is imaged by a lens on a CCD line mounted to one side of the laser

Depending on the distance between laser and measured object, the position of the exposed pixels on the CCD line changes

The exposed pixels are evaluated and the dimension of the relevant object status is determined by processing sig-nals via a digital signal processor (DSP)

The calculated distances are output or queried via the RS485 bus and the analog output

In addition, the limit values of the measured values can be monitored To this end, two limit value outputs are imple-mented whose respective limit values can be set in the di-agnostic and parametrisation tool under "Filters / Limit Values"

All objects which are neither very reflective nor transparent can be measured

Fig 4-1: Measuring principle (diagram)

The computer used for the diagnostic and parametrisation tool software must have an RS485 interface, e.g the USB-to-RS485 adapter from LAP For further information

please refer to chapter 14.1 of this operation manual

Information on the wiring of the laser sensors and the functions of the display LEDs is presented in chapter 4.2.4

The POLARIS laser sensors can also be operated via the digital intermediate transfer module POLARIS CONNECT

or POLARIS HUB module For notes and information on this, refer to the corresponding description of functions and operation

4.1.2 Thickness measurement using two laser sensors

Thickness measurements are possible using two POLARIS laser sensors In this case the user must ensure that the surface of the measured object never leaves the measuring range of the corresponding laser sensor on ei-ther side of the measured object (see Fig 4-1: Represen-tation of the measuring ranges)

Each laser sensor must therefore be mounted so that the end of its measuring range covers the surface of the measured object at the farthest possible distance

The measured value 0 corresponds to the point farthest away The measured values increase towards the POLA-RIS

In the marginal case of an absolutely flat, extremely thin measured object, the clear width is the sum of the dis-tances of both ends of the measuring range

The middle of the measuring range and the clear width are shown in the following diagram for the sake of clarification

1 Reference surface

2 Measuring distance

3 Start (upper sensor) and end (lower sensor) of measuring range

4 Middle of the measuring range

5 End (upper sensor) and start (lower sensor) of measuring range

6 Clear width for thickness measurement

7 Measured object

Fig 4-1: Representation of the measuring ranges

The installation dimensions for the respective model sizes are listed in the following table

dis-Middle of measuring range (mm)

End of measuring range (mm)

Clear width tween the laser sensors for thick- ness measurement (mm)

Tab 4-1: POLARIS installation dimensions

Note regarding thickness measurement: Add the minimum product thickness to the clear width

4.1.3 Converting the sensor value to a measured value

The value range of the sensors is 2768 to 62768 and is independent of the sensor's measuring range The value

2768 corresponds to the end of the measuring range that

is farthest away from the sensor and the value 62768 responds to the end that is closest to the sensor

cor-The actual measured value in mm is obtained by ing 2768 from the sensor value and then multiplying the difference by the sensor's measuring range and dividing

subtract-by the resolution (60000) The following equation can be used:

Fig 4-2: Measured value formula

This yields the settings for the Wetec display converter:

• Scale factor = measuring range / 60000

• Offset = 2768 x measuring range / 60000 This results in the following for the inverse representation

of the measured value:

Fig 4-3: Measured value formula (inverse)

This yields the settings for the Wetec display converter:

• Scale factor = -measuring range / 60000

• Offset = 62768 x measuring range / 60000 Factors for the standard measuring ranges:

ing range

Measur-Scale factor

Fig 4-4: Dimensions of the POLARIS laser sensor

4.1.5 Technical data

Operating voltage 18 … 30 VDC

Current consumption Max 250 mA

Laser power 1 mW (optional 3 … 7 mW)

Laser class 2, 3R or 3B; observe laser warning label

Laser source Laser diode 670 nm (red)

Life expectancy more than 30,000 hours of operation

(at T=25 °C)

Measuring frequency 300 Hz ≤ 4 kHz Data formats SynchroNet, FastBin, ASCII decimal

Interface RS485, opto-isolated, up to 960 kBaud

Contacting Coninvers connector, 9-pin

Analog output

4 … 20 mA

Max burden 470 Ω Limit value outputs ≤ 50 mA, common feed Vcc International Protection

Rating IP65

Dimensions L x W x H 168 x 109 x 39 mm

Weight 1100 g

Ambient light (operation)

≤ 3000 Lux

Ambient temperature (operation)

0 °C to +40 °C

Humidity (operation)

35% to 85% rel humidity, non-condensing

Tab 4-3: General POLARIS data

Comments regarding measuring frequency: With the fault factory settings, the POLARIS DSP controls both the laser power and, if that is insufficient, the exposure time of the CCD line in real time to obtain the optimum measure-ment results If the application requires, a fixed exposure time of 250 µs is possible

4.1.6 Model overview

Model/type

ing range [mm]

ing dis- tance [mm]

Measur- lution [μm]

Reso-Repeat accuracy (over time)*

[μm]

ing un- certainty [μm]*/%**

Measur-Min /Max measuring point width [μm]

* Derived from DIN 32877, averaging of 64 individual values **In % of

the measuring range

Tab 4-4: POLARIS measuring ranges and basic clearances

to an ambient temperature of 20°C, measured on a matt white surface and an integration time of 100ms,

• Measuring point width: Dimension of the spot parallel

to the laser sensor cover

4.2.1 Description of the outputs

An RS485 bus, a limit value output and an analog output are provided as outputs

Circuit diagram of the limit value outputs:

Two outputs form a supply group with the same external supply potential

Fig 4-5: Output group

4.2.2 Data output format

The LAP SynchroNet protocol is used by default for the communication between the POLARIS laser sensors

This protocol was developed for the communication of LAP laser sensors of the POLARIS series via the RS485 interface and is especially designed for a high data trans-mission rate with little protocol overhead and greatest possible flexibility and system openness for future devel-opments

To achieve the lowest possible redundancy during mission, the data are transmitted in binary format For the clear differentiation of data and addresses the address bytes receive a parity bit set to on and the data a parity bit set to off

trans-Each POLARIS laser sensor represents an individual scriber in the RS485 network Each laser sensor is as-signed a dedicated address and a subsequent subscriber The sending of a network address is simultaneously the token transfer to the addressed device

sub-The following output value is reserved for diagnostics in the SynchroNet format:

FFFF Hex "No object in measuring range"

Explanation regarding the analog output:

Once the object leaves the measuring range, the last valid measured value is maintained for a period of five exposure times (the length of exposure time corresponds to the starting value) This value can be found in the provided parameter listing The initial current then returns to the quiescent value of 2 mA

If a new object enters the measuring range, the new value

is available at the output after expiration of an exposure time

Explanation regarding the RS485 interface:

As soon as the object leaves the measuring range, the value 65534Dec is output

If a new object enters the measuring range, the new value

is available at the RS485 bus after the expiration of an posure time The length corresponds to the set exposure start time

ex-4.2.3 Cable/Connector pin assignment

Fig 4-6: Cable assignment of the laser sensor

The following table illustrates the connector cable/pin signment:

as-Pin Colour Signal Explanation

1 White + 24 V Power supply + 24 V

2 Brown GND Power supply earth

3 Green RS485 a RS485 a from previous transceiver

Grey RS485 a RS485 a to next transceiver

4 Yellow RS485 b RS485 b from previous transceiver

Pink RS485 b RS485 b to next transceiver

5 Blue GND RS485 Earth of RS485 bus

Black GND analog Earth of output signal 4 … 20 mA

6 Purple Out analog Output signal 4 … 20 mA

7 Red Vcc 5 … 30 VDC for limit values A and B

8 Red/blue Limit A Limit value output A

9 Grey/pink Limit B Limit value output B

Tab 4-5: Cable and pin assignment

Once the system has been wired up correctly and the erating voltage has been applied, you can test the device functions via the integrated function LEDs

op-The POLARIS laser sensor has three LEDs for displaying the status The following table illustrates their meaning

Meaning of LEDs Colour Function

Yellow The yellow LED shines when an object is identified in the

measuring range

Green

The green LED shines when the laser sensor is turned on

To make it easier to align the laser sensor, the LED flashes when an object is recognised as being in the middle of the measuring range

nor-Tab 4-6: Meaning of LED displays

Once the adjustments are complete, the measuring tem can be used for normal operation

POLARIS laser sensors support three different operating modes These three modes and their uses are described below

One POLARIS laser sensor is used for distance urement in an individual application (single mode) In this case the measured values are queried at the analog out-put or the RS485 interface This mode corresponds to the default factory setting of the laser sensor

meas-The single mode represents a special case that is not network-compatible It is used for automatic sending of measured values, preferably in the ASCII format and scaled in mm

Two laser sensors are used for single-track thickness measurement (master-slave mode) In this case the two laser sensors must work in master-slave mode

The slave laser sensor determines the distance to the ject and transmits this value to the master sensor via the RS485 bus The master laser sensor offsets the trans-ferred value against its measured value and outputs the resulting thickness to the analog output or the bus