Www.balluff.com Automatikai építőelemek 10.08.2014Balluff Kft, CIM Veszprém, Z. Pólik1 Pólik Zoltán Kutató-fejlesztő mérnök Corporate Innovation Management,

www.balluff.com

Automatikai építőelemek

10.08.2014 Balluff Kft, CIM Veszprém, Z. Pólik 1

Pólik Zoltán

Kutató-fejlesztő mérnök

Corporate Innovation Management, Veszprém

BALLUFF Elektronika Kft.

Veszprém

[email protected]

Ultrahangos, magnetorstrikciós érzékelők

Irodalom:

[1] Lambert Miklós: Szenzorok – elmélet és gyakorlat[2] Oláh Ferenc, Rózsa Gábor: Automatikai építőelemek[3] Balluff katalógusok

http://www.balluff.com/

mailto:[email protected]



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BUSUltrasonic Sensors

Basics


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AgendaThese questions and topics are covered in the Ultrasound Basic Training

What is ultrasound? How does ultrasound propagate? Infrasound – audible sound – Ultrasound – Hypersound Propagation in a medium Propagation in air How does an Ultrasonic Sensor function? Coverage of an Ultrasonic Sensor Limitation of the switching distance How fast is an ultrasound wave? Reflection and Absorbtion of an ultrasound wave What to consider if using Ultrasonic Sensors in applications? Ultrasonic Sensors in nature Industries and Applications


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What is ultrasound?

To answer this question you need to know first what sound actually is.

Known Encyclopedias explain:

1. Accoustic sound

2. (Physic) a propagating wave with sine oscillation in a medium that can be heard

The sound is a mechanical wave. If you take a closer look then you notice that sound is a

oscillation of pressure and density in a medium.

If you speak, the sound will propagate through the air.


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How does Ultrasound propagate?

Sound has 2 kinds of propagations

in a medium:

1. As a longitudinal wave

2. As a transversal wave

Longitudinal propagation is possible in

gas and liquid.

Both propagations are possible in solid

mediums.

longitudinal wave transversal wave

t


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Infrasound – audible sound – Ultrasound – Hypersound

Sound is classified in different category groups depending on frequencies:

Infrasound less then 16 Hz

Audible sound between 16 Hz and approx. 20 kHz

Ultrasound between 20 kHz and approx. 1 Ghz

Hypersound more then 1 Ghz

The frequency interval between 16 Hz and 20 kHz is the audible sound that

a human can hear. The older a human is the less he can hear higher

frequencies.


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Propagation in a medium

If the sound is a mechanical wave then it needs a medium. Which means in

turn that there is no sound in vacuum.

But sound can propagate in any different mediums (gas, liquid and solid

mediums) and even swap from one to another medium. The best known

example for that effect is the tin can telephone.


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Propagation in air

Ultrasonic Sensors are mostly designed for usage in the medium air. There

are also special types.

Ultrasonic Sensors emit a focused field. This field is getting larger with

longer distance. The further the field the less power is there, relative to an

area.


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This has two reasons:

1. The sound spreads in the area. The original power is getting less. Example:

Inflating a Balloon. The skin gets thinner the bigger the ballon gets.

2. The sound energy is getting absorbed by air. Heat is generated by the

rubbing/oscillating of the air molecules.

These are the two reasons why the detection range of an Ultrasonic Sensor

is limited.

Propagation in air


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How does an Ultrasonic Sensor function?

The Ultrasound is generated e.g. with a piezo element.

If voltage is applied to the piezo element it will oscillate and generate

Ultrasound. The item works as a speaker.

With the impact of Ultrasound waves on a piezo element a oscillating

voltage is generated. That effect is explained with the piezoelectric effect.

The item works as microphone.

TransducerTrigger

Amplifier


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An Ultrasonic Sensor is comparable with a optical diffuse sensor.

• Ultrasound is generated with the piezo element.

The piezo element still oscillates after turning of the voltage. In this time no Echo can be detected.

That means the sensor has a blind zone!


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• The Ultrasound wave hits a medium and gets reflected.

• The Echo hits the piezo element.

The sound speed is known in a specific medium. You can measure the time between emission and reception. With these data the distance of the object can be calculated.


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That‘s why the ambient

temperature should not vary

or vary slowly. The sound

speed depends on the

ambient temperature. If it

varies slowly the sensor can

compensate this effect with its

electronics.


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Coverage of an Ultrasonic Sensor

type: M12 Sensor

Switching Distance: 25 mm – 200 mm

Measuring plate A: 100 x 100 mm

Round rod B: Ø 25 mm


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Plate rod sensor

type: M12 Sensor

Switching Distance: 25 mm – 200 mm

Measuring plate A: 100 x 100 mm

Round rod B: Ø 25 mm

Ultrasound cone


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The opening angle defines the 3db limit. Objects which are not within the 8° opening angle can still be detected but they must be in the near field.

(see previous slide).


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Ultrasonic Sensors with higher frequencies have shorter and more focused sound cones.

100 kHz 200 kHz 300 kHz

That‘s why they are ablte to detect smaller objects!


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Limitation of switching distance

The damping of sound in air depends on the following three factors:

1. Sound Frequency

2. Air Temperature

3. Air Humidity

4. Air pressure


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The higher the sound frequency, the lower the switching distance.

Switching distance vs Frequency

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

0 100 200 300 400 500 600 700

sound frequency in kHz

swit

chin

g d

ista

nce

in

mm

1. Sound Frequency

2. Air Temperature

3. Air Humidity

4. Air pressure


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The higher the air temperature and humidity, the lower is the switching

distance.

This relation is simplified!

If yo have an application with a change of air

temperature and air humidity you have to pay

attention. The Ultrasonic Sensor varies his

switching distance with the change of

environmental conditions. That could cause

wrong switching operations.

1. Sound Frequency

2. Air Temperature

3. Air Humidity

4. Air pressure


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At higher air pressure, the damping is less. Consequently the sensor has a

greater range!

Attention: The Ultrasonic Sensor but must be

designed for positive/negative pressure.1. Sound Frequency

2. Air Temperature

3. Air Humidity

4. Air pressure


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How fast is a Ultrasound wave?

The sound speed depends on the medium!

sound speed (longitudinal) for different mediums

342

500

1483

2250

3300

5180

5400

80

1740

2670

4700

0 1000 2000 3000 4000 5000 6000

PVC-P

Air (20°C)

Cork

Water (20°C)

Oil

PVC-U

acrylic glass

beech wood

oak wood

steel

quartz glass

sound speed in m/s


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Since most Ultrasonic Sensors, as mentioned earlier, are used in air the consideration of other mediums is not necessary:

Sound speed in air

295

315

335

355

375

395

415

435

-55 -5 45 95 145 195

temperature in °C

sou

nd

sp

eed

in

m/s


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As can be seen from the formula, the temperature has a large influence on the

speed of sound! This can be compensated within the sensor with its electronic

circuit. Condition is, however, that the change of temperature takes place not to quickly.

sound speed in air

295

315

335

355

375

395

415

435

-55 -5 45 95 145 195

temperature in °C

soun

d sp

eed

in m

/s



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Reflection and Absorbtion of an Ultrasound wave

Distinction of surfaces in „sound hard“ and „sound soft“

Ultrasound waves propagate in air with their specific speed. If these sound waves hit

a medium with a different sound speed (see slide with sound speeds) then there will

be a reflection of the sound.

„Sound hard“

The sound will be reflected if the sound speed in the new medium is higher than in the

previous one.

„Sound soft“

The sound will be absorbed if the sound speed in the new medium is less than in the

Previous one.


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Important!

• Soft and airy materials have a bad reflection• Soft, thin materials can be permeable for the Ultrasound.• On the contrary hard materials have a good reflection.

Good reflecting materials Poorly reflecting materials

Water, Color / varnish, concrete, Metal, wood, glass,hard foam, plastic

Soft carpets, cotton woolsoft clothsSoap water - beer foamsoft foam, felt


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Important

However, almost all objects can be detected, also those with a bad

reflectance. But on those objects you have to accept the reduction of the

switching distance.

The detection properties of an object are independent of color, gloss and

transperancy, but depend on the surface properties.



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1. Case – plane surface

2. Case – rough surface

Incident angle is equal to emergent angle!

The surface is considered as rough if the roughness is in the order of the wavelength λ.

Tends to be higher.

frequency λ (air)

80 kHz 4,3 mm

130 kHz 2,6 mm

200 kHz 1,7 mm

300 kHz 1,1 mm

400 kHz 0,8 mm


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3. Case – plane Surface, Tilted Sensor


4. Case – roug Surface, Tilted Sensor

On the plane surface the Ultrasound wave is reflected completly away. Tilting of max. 3° is allowed.

Rough surfaces are less sensitive to tilting. You can tilt the sensor significantly more than 3°.


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Examples for rough and plane surfaces

Plane surface Rough surface

Pane Sand

paper sugar

Wood plate gravel

Plastic foil Air bubble film

varnished surface stucco

tile rough sawn wood

Bulk good has usually a rough surface that‘s why it reflects always diffuse! Bulk materials are therefore clearly detectable.


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What to consider if using Ultrasonic Sensors in applications?

Ambiente temperature?

You can use a Ultrasonic Sensor in warm and cold ambiente temperature.

Temperature changes have to process slowly so the sensor can compensate it.

The switching distance changes if the ambiente temperature changes.

Hot Objects?

Detecting hot objects can be difficult. The air turbulence weaken the sound so that it

can hardly or not be received.

Air pressure Variations?

Ultrasonic Sensors can not be used in vacuum. With positive air pressure

the absorbtions gets less, with negative air pressure the absorbtions

increases dramatically. This changes the range of the sensor. In principle you

can use the sensor in positive and (minor) negative pressure however the sensor

must be designed for that case.


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Rain and humidity?

Ultrasonic Sensors can be partially used in rain. The transducer surface

should be kept dry. In humid areas the sound speed changes.

Convex surfaces?

The ultrasound gets reflected in all areas. The maximum distance range

continues to decrease with a smaller radius.

Liquid?

You can detect liquids with a Ultrasonic Sensor. The beam axis must not

deviate by more than 3° from vertical relative to the liquid surface.


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Strong air movements and turbulences?

This leads to instability in the measurement. Air velocities of few meter per

second are not critical. You have to try!

Redirecting of the sound?

Redirecting is possible with hard plane surfaces (like metal). With this

feature you can solve applications where the object can’t be reached

easily. But the maximum range decreases. The sound should not be

redirected more than 2 times.


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Sensors in Nature

Bats

Orientation with Ultrasound waves. The bat detects the time difference

between the arrival of the echo in the left and right ear. With that

information it can position the object around him.

Humans

We are capable to position things like the bat. But not as good as it.

Whales and dolphins

Locating fish under water.


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Industries for Ultrasonic Sensors

• Handling und Automation

• Special machinery

• Automotive Industry

• Filling and packaging

• pharmaceutical industry

• Plastic and rubber industry

• Wood and furniture industry

• Paper and Printing Industry

Adatlap M30

Adatlap M18


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Applications

Setting the foil hag!

z.B.:


• textile industry


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Applications

Monitoring of filling level!

z.B.:

• Filling and packaging

• Special machinery


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Applications

Measuring the roll diameter!

z.B.:


• Packaging


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Applications

Monitoring the distance!

z.B.:

• Automotive Industry

• metal processing


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Applications

Detect and Count!

z.B.:

• Packaging



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Applications

Measure stack height!

z.B.:

• Packaging



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Why Use Continuous Linear Positioning?

Constant growth in automation technology has produced several trends:

The need for non-contact wear-free sensors to ensure greater machine uptime A switch from simple binary/discrete switching to continuous measurement sensors Higher accuracy and production rates

These trends will continue to grow rapidly in the quest for faster and more efficient machines.


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Uses for Linear Position Feedback

Three Major Fields of Applications:

1. Control Linear Motion /Closed-Loop Servo Motion Control(i.e. applications requiring high moving dynamics, and high position repeat accuracy)

2. Monitor Linear Position(i.e. Applications requiringprecise positioning, and highposition repeat accuracy)

3. Make Measurements(i.e. Applications requiring preciselinearity for measurement ofgeometrical shapes)

Example:Move it fast, then slow down,

then move fast again

Example:Cut to defined Length

Example:Did it get there yet?

Is it all the way back?How far did it move?


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MICROPULSE Transducers - BTL… extremely rugged and reliable

Balluff MICROPULSE Transducers …

are position sensing devices designed to provide linear position feedback

operate 100% contactless and are therefore wear- and maintenance-free

are extremely rugged and reliable

Operating Principle = Magnetostriction


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What is Magnetostriction?

Mechanical wave

Electromagnetic field

Dampingelement

Position marker (magnet)

Mechanical wave

Signal converter (Balluff patented process)

ReceiverMagnetostriction

wire

Initialpulse

Waveguide

A magnetic field has the effect of locally deforming the wave guide.

This effect is called magnetostriction.


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How does Magnetostriction function?

1. The magnetic field of a permanent magnet has theeffect of locally deforming thewave guide.

2. The short current pulse throughthe copper conductor causes amagnetic field.

3. This magnetic field interfereswith the existing field of thepermanent magnet(position element).

4. In result, an ultrasonic waveis generated.

5. The sonic wave travels alongthe waveguide until it is detected by the pickup.

6. The time between the start of the pulse and receiving of the receiver impulse is measured. The elapsed time indicated by the timer then represents the distance between the position magnet and the pickup.


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Components of Magnetostrictive Technology

Power- +

Counter

Start

StopD/A

PowerReg

N

S

Wave GuidePick-up Coil

Damping element

Magnet


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Transducer Operation

Power- +

Counter

Start

StopD/A

PowerReg N

S

Taking a measurementAdatlap


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Available Interfaces

Voltage 0 to10 V

-10 to +10 V

Current 4 to 20 mA 0 to 20 mA

Pulse START/STOP

DPI / IP PWM

Synchronous Serial 16, 24 or 25 bit

Network OptionsAnalog Output

Digital Output

Digital I/O 4 programmable

switched outputs

Quadrature Interfaces directly to

standard encoders

BUS interface modules WAGO

Phoenix ContactMade in

DeviceNet

CANopen

PROFIBUS DP

VARANNEW!!


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Active Stroke

Analog Interface

Analog type BTL transducersare available in various output configurations:

0...10 V -5…+5V -10...10 V 4...20 mA, 0...20 mA

Analog outputs

Made in

transducers with :• Voltage output have 2 outputs, one rising and one falling.

• Current output are available with 1 rising or falling output signal.


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Analog Interface … the Characteristics

Characteristics: Popular wide spread standard signal Can be processed by every PLC or other control system A standard feedback signal used in control engineering Cable break monitoring possible via 4-20 mA-signal Resolution 0,1 mV / 1,6 µA (typical values depending on BTL style) Operation using rising or falling signal output mode

Restrictions regarding cable length must be observed Observe installation guidelines to avoid problems concerning

Electromagnetic compatibility (EMC)


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Analog Interface:Basic operation “Rising” Output

0V 10V5V

“Rising” Output

0V 10V5V

Mag

net

Magnet is attached to:

Moving Machine Part (e.g. piston of hydraulic or pneumatic Cylinder)

Float (Liquid Level)

Output signal goes to: PLC Analog Input Card

Motion Controller Digital Display, …etc.

UA (Pin 5)


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Analog Interface:Basic operation “Falling” Output

Mag

net

10V 0V

“Falling” Output

5V

Magnet is attached to:

Moving Machine Part (e.g. piston of hydraulic or pneumatic Cylinder)

Float (Liquid Level)

Output signal goes to: PLC Analog Input Card

Motion Controller Digital Display, …etc.

UA (Pin 3)


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1 to 3 µsecInterrogation pulse

START / STOP Operation

Digital P(ulse) Interface:Basic Operation (Start / Stop and Gate)

5V

0V

0V

5V

PLC, Motion Controller

or Interface Module

Pulse-Width-Modulated (PWM) “Gate”- Operation

Benefits:

• High Noise Immunity

• Native Signal• Lower Cost


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Digital P(ulse) Interface … the Characteristics

Characteristics: Cost-effective Trouble-free RS-485 differential

output signal transmission Position resolution 1µm Noise-immune up to 500m Absolute distance measurement value

Block diagram of Digital Pulse-Interface

Digital output versions available:

Do not use fornew applications.

I, K, and L types will be phased

out shortly.


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High-accuracy digitizing chip for pulse interface

High-accuracy digitizing chip for pulse interface Balluff digitizing chip available for companies developing

their own control and processing electronics interface. Position data from 4 magnets can be processed simultaneously High-resolution 1µm

BalluffDigitizing

Chip 44QFP

P-pulsesignal

MICROPULSE transducer with 1 to 4 Magnets

Controller or Processing electronics

4 / 8bit bus

1 2 43


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P111 Interface with DPI / IP Protocol

• DPI / IP (Digital Pulse Interface / Integrated Protocol) for direct data interchange between controller and transducer.

• Signal lines are used to send additional information (i.e. manufacturer, serial number, stroke length, gradient).

Features include: Bi-directional communication Transducer controlled using Init

and Start/Stop signals Integrated diagnostic functions Plug and Play Automatic parameterization reduces downtimes Sending of sensor model, stroke length,

specific parameters

Cost savings using DPI / IP for start-up and installation

AT -Series


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SSI Interface … the Characteristics

Characteristics Standard SSI (Synchronous Serial Interface): Synchronous serial data transmission for variety of controls. Noise immune RS-485/ 422 differential line drivers and receivers. Reliable signal transmission over cable lengths of up to 400 meters

between control and BTL transducer.


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Digital I/O Interface … the Characteristics

Characteristics: 4 switched digital outputs (PNP / NPN) 100mA load current / Output 4 switchpoints / cams freely programmable

via removable calibration device or via 2 programming inputs.

High resolution and repeatability. Value update: 1 KHz : stroke ≤ 1300 mm 500 Hz : stroke > 1300 mm Noise immune IP 67 per IEC 60529 Eliminate multiple external proximity sensors, Auto-Tuning™ circuitry allows use of Balluff or

competitors’ magnets Connection to controller max. cable length 500 m


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Characteristics: Evaluation of up to 4 Magnets simultaneously Intelligent transducer recognizes itself the

number of magnets currently active Data transmitted includes: 4 x current magnet position 4 x current magnet velocity Status of 4 freely programmable cams. High data security Resolution 5µm (Standard), BUS configurable Device address can be set by DIP switch. Less and simple wiring Signal transmission over distances of up to

2500 m (1200m PROFIBUS)

Network Interface:CANopen, DeviceNet, PROFIBUS

111001010101

0110101001

111001010101

0110101001

Power


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The New PROFIBUS BTL Bus Coupler:BNI PBS-551… / BNI PBS-552…

Two new BNI PBS decentral input modulesfor connecting to Profibus-DP Network

BNI PBS-551… connects: up to 4 MICROPULSE transducers with M1 or P111 interface and up to 8 Standard digital sensors

BNI PBS-552… connects: up to 4 MICROPULSE transducers with M1 or P111 interface and up to 4 Standard analog voltage and / or current type sensors

INDUSTRIAL NETWORKING

Economically connect BTL transducers to Profibus!!


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How the BNI PBS-551… / BNI PBS-552…Interfaces to the PROFIBUS

Power

0110101001

111001010101

Balluff BTL_-P-111/ M1 Transducers

Balluff BTL5- T…. Profibus Transducers


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Potentiometer

Stroke 1

NewConducting Layer

Stroke n

Unchanging Performance !BTL

IP67

Benefits of MICROPULSE Technology

100% contact-less and wear-free

Effectscaused by

wear, scratches


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Kialakítások


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Alkalmazások


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Alkalmazások


Documents

Www.balluff.com Automatikai építőelemek 10.08.2014Balluff Kft, CIM Veszprém, Z. Pólik1 Pólik Zoltán Kutató-fejlesztő mérnök Corporate Innovation Management,