Proximity sensor terminology Function description of the inductive proximity switch An inductive proximity switch consists mainly of three functional groups: 1. Oscillator 2. Trigger circuit 3. Output switching device As soon as a supply voltage is applied, the oscillator begins to swing and takes on a defined current. The electromagnetic field produced by the oscillator coil is oriented by a ferrite core. The effective field of the sensor is thereby focused through the active face of the sensor. If a target made of an electrically conductive material is positioned near the active face, eddy currents are induced within this target. The resulting power loss leads to a reduction in the quality factor of the resonant circuit and the oscillator amplitude consequently falls. This is evaluated by the trigger circuit, which activates the the output switching device once a certain amplitude is reached. Definition of the sensing range EN 60947-5-2 defines the sensing range for all types of proximity switches apart from slot and ring types. There are two ways of operating a proximity switch: • axially approaching objects • radially approaching objects The following definitions only apply to axial operation. Nominal sensing range s n The nominal sensing range (according to EN 60947-2-5 "Rated Sensing Range") is a standard value for determining the operating distance. It does not take into account process tolerances or changes due to outside influences such as voltage and temperature. Hysteresis H Distance between the switching points at which the target approaches and moves away from the proximity switch. Proximity sensor terminology Blackburn Office - 01254 685900 Chippenham Office - 01249 460099 30 PROXIMITY SENSORS Have you ordered your cables and accessories? We can supply everything you need to complete your project, turn to pages 81 to 84 for our full range
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Proximity sensor terminologyFunction description of theinductive proximity switchAn inductive proximity switch consistsmainly of three functional groups:1. Oscillator2. Trigger circuit3. Output switching deviceAs soon as a supply voltage is applied, theoscillator begins to swing and takes on adefined current.
The electromagnetic field produced bythe oscillator coil is oriented by a ferritecore. The effective field of the sensor isthereby focused through the active faceof the sensor.
If a target made of an electricallyconductive material is positioned near theactive face, eddy currents are inducedwithin this target. The resulting power lossleads to a reduction in the quality factor ofthe resonant circuit and the oscillatoramplitude consequently falls. This isevaluated by the trigger circuit, whichactivates the the output switching deviceonce a certain amplitude is reached.
Definition of the sensing rangeEN 60947-5-2 defines the sensing rangefor all types of proximity switches apartfrom slot and ring types.There are two ways of operating aproximity switch:• axially approaching objects• radially approaching objects
The following definitions only apply to axialoperation.
Nominal sensing range snThe nominal sensing range (according toEN 60947-2-5 "Rated Sensing Range") is astandard value for determining theoperating distance. It does not take intoaccount process tolerances or changes dueto outside influences such as voltage andtemperature.
Hysteresis HDistance between the switching points atwhich the target approaches and movesaway from the proximity switch.
We can supply everything you need to complete yourproject, turn to pages 81 to 84 for our full range
Proximity sensor application tipsInfluences on thesensing rangeBesides its dimensions, the materialcomposition of the target also plays animportant role. This is described by thereduction factor. The reduction factor isthe factor by which the sensing range isreduced based on different materials. FE360 (St37 steel) is the reference materialfor inductive proximity switches and aground plate for capacitive proximityswitches. The smaller the reduction factor,the smaller the sensing range for thespecific material. This reduction factor canvary depending on the housing andshielding material, among other criteria.For this reason, the customer should referto the value in the relevant data sheet.For inductive proximity switches, thefollowing table contains some typical valuesfor the reduction factor:
Condition for installation
Cylindrical proximity switchesDevices with the same diameter can havedifferent sensing ranges. The followingtable shows some typical examples:
Non-embeddable proximityswitchesNon-embeddable proximity switches havethe greatest sensing range (based on thediameter). Coils are used to generateelectromagnetic fields in inductiveproximity switches. A portion of this field isstill radiated laterally, however. A lateraleffect can also be observed in capacitiveproximity switches.In order to prevent these high-rangeproducts from being damped by theirenvironment, a space must be left aroundthe sensor element. This space mustconform to the minimum requirementsshown in the following table.
In capacitive proximity sensors, thefollowing table contains some typical valuesfor the reduction factor:
Embeddableproximity switchesEmbeddable inductive and capacitiveproximity switches can be installed withoutleaving a space (A=0). The advantage isthat they are better mechanically protectedand less prone to errors than non-embeddable types. The necessaryreduction of the lateral radiation of the fieldis obtained by special internal shielding.This entails a loss of range. Theseproximity switches only achieve about60% of the sensing range ofnonembeddable models.
The switching characteristics of magneticfield sensors are practically unaffected bythe mounting conditions, as long as thesurrounding material is non-magnetisable.
Mutual interferenceThe minimum distances F listed in theabove table must be maintained in orderto prevent mutual interference. Proximityswitches with altered frequencies are alsoavailable on request in case these distancescause application-related problems. Theycan be mounted directly adjacent to eachother. In case of doubt, please contact us.
Sensing RangeEmbeddable Non- Increased
embeddable Sensing Range
6.5 1.5 2 -8 1.5 2 312 2 4 618 5 8 1230 10 15 22
Diametermm
Model Dimensions [mm] A B F
Embed. F = DInd. 2 x Sn 3 x D Non-embeddable
F = 3 x DCap. Plastics Metal Plastics MetalCJ1 5 15 15 30 60CJ4 20 35 80 120 60CJ2 15 50 30 60 100CJ6 40 50 80 160 100
This housing design was introduced byPepperl & Fuchs under the brand nameVariKont and VariKont M. The VariKontconsists of a robust base enclosure (PBTor metal) which is screwed onto themounting surface and contains the terminalconnections. The top part which is madeof PBT, is sealed against the base enclosurewith neoprene and carries the encodedconnector. The top part contains theswitch amplifier.
The sensor head is convertible in fivedirections, i.e. the active surface can bedirected forward, right, left, up or down.
Varikont a.c. and d.c. powered sensorsSensing Switch Type Installation Connection Output Switching Supply Output Order Code Price 1+ Price 5+Distance Dimensions Type Type Current Frequency Type15mm Varikont (1) Flush Terminal 200mA 150Hz 10-60V d.c. NPN NJ15+U1+E £43.47 £39.13
40mm Varikont (2) Non-Flush Terminal 8-500mA 20Hz 20-253V a.c. N/O or N/C NJ40+U1+W £82.80 £74.52
Sensing Switch Type Installation Connection Output Switching Supply Output Order Code Price 1+ Price 5+Distance Dimensions Type Type Current Frequency Type20mm Varikont L Flush 4 pin M12 200mA 150Hz 10-30V d.c. PNP NBB20-L2-E2-V1 £28.47 £25.63
Sensing Switch Type Installation Connection Output Switching Supply Output Order Code Price 1+ Price 5+Distance Dimensions Type Type Current Frequency Type15mm Varikont M Non-Flush Terminal 200mA 500Hz 10-60V d.c. PNP NCN15+M1K+E5 £51.80 £46.62
Nowadays, it is possible to obtain binaryswitching in proximity sensors(simultaneous changes in the switch statusof sensor and amplifier) by using the latesttechnology while maintaining the standardvoltage and current values.
NAMUR proximity sensorsNamur InterfaceNAMUR* proximity sensors traditionallyhave a constant current path characteristic.
*NAMUR: Normenarbeitsgemeinschaft für Mess- undRegelungstechnik der chemischen Industrie (StandardsWorking Group for Control and Instrumentation in theChemical Industry).
Intrinsic SafetyThe characteristic voltage and currentvalues are kept at such a low level that the
NAMUR* proximity sensor canbe used in potentially explosiveenvironments ("intrinsic" type ofprotection). This product seriesis identified by an N at the endof the code, sometimes incombination with a number.
The power limiting function isimplemented in the respectiveapparatus. This means that thecircuit containing a NAMURproximity sensor is onlyintrinsically safe if it is suppliedvia a suitable isolation amplifier.The conformity of the electricalcharacteristics of proximitysensors and isolation amplifiersis ascertained by an "intrinsic
safety test". The cable inductivity andcapacitance are included in this test as theyconstitute energystores.
For more information on explosionprotection and intrinsic safety, pleasecontact our sales department.
What is ATEX?- ATmosphere EXplosiveThe founding treaty of the EuropeanEconomic Community includes articles 95and 137, which form the basis for 2 EUdirectives:Directive 94/9/EC (also known as ATEX100a) of 23.03.94 harmonisation of thelegal regulations of member states withrespect to equipment and protectivesystems designed for use in potentiallyexplosive environments.Applicable since 01.03.1996Directive 1999/92/EC of 16.12.1999minimum requirements for improving thehealth and safety of employees at risk frompotentially explosive atmospheres.Applicable since 28.01.2000.This directive does not apply to themanufacturers of explosion-protecteddevices and is therefore not relevant to thecatalogue.
What does the directive94/9/EC stipulate?• Definition of device groups I and II.• Definition of device categories(classification of devices according tohazardous areas)
• Conformity evaluation procedure (whichmanufacturers are allowed to producedevices in which category)
• Transitional period until 30.06.2003.• From 01.07.2003 onwards, onlyDirective 94/9/EC will apply!
What consequences doesdirective 94/9/EC have for thelegal situation?Previous situation:European-wide constructionalrequirements (type of protection) foroperating material.National installation requirements.
New situation:No national variations!
This means:• Zones 0, 1, 2 for areas at risk fromgas explosions.
• Zones 20, 21, 22 for areas at risk fromdust explosions.
• No zone classification for areas used formedical purposes.
Our expert technicalsupport is totally free!Call our support hotline on 01254 685900 to
speak to our technical support engineers
Switch/sensor input relay outputFeatures�1 - channel�Control circuit EEx ia IIC�Reversible mode of operation�1 signal output with 1changeover contact
�EMC acc. to NAMUR NE 21
FunctionThe transformer isolated barrier transfersdigital signals from the hazardous area.Sensors per DIN EN 60947-5-6(NAMUR) or mechanical contacts may beused as alarms. The control circuit ismonitored for lead breakage (LB). AC unitshave a low heat build-up due to voltagepeak value generation. The input is safelyisolated from the output and the powersupply (DIN EN 50020). The output andpower supply are safely isolated from eachother (DIN VDE 106 Section 101).
Technical specification KFD2-SR2-Ex1.W KFA5-SR2-Ex1.W KFA6-SR2-Ex1.WConnection type Power rail or terminals 14+, 15- Terminals 14, 15 Terminals 14, 15Rated operational voltage Ue 20... 30 V DC 103.5.. 126 V AC, 45.. 65Hz 207.. 253 V AC, 45.. 65HzRipple 10 % - -Rated operational current 20 ... 23 mA - -Power consumption - 1W 1WDetails of certificate of conformity Certification number PTB 00 Certification number PTB 00 Certification number PTB 00
ATEX 2080; for additional ATEX 2081; for additional ATEX 2081; for additionalcertifications contact sales certifications contact sales certifications contact sales
Group, category, ignitionprotection method II (1) G D [EEx ia] IIC II (1) G D [EEx ia] IIC II (1) G D [EEx ia] IICVoltage Uo 10.5 V 10.6 V 10.6 VCurrent Io 13 mA 19.1 mA 19.1 mAPower Po 34 mW 51 mW 51 mW
Output (not intrinsically safe)Output Signal; Relay Signal; Relay Signal; RelayContact loading 253 V AC / 2 A / cosϕ > 0.7; 253 V AC / 2 A / cosϕ > 0.7; 253 V AC / 2 A / cosϕ > 0.7;
40 V DC / 2 A resistive load 40 V DC / 2 A resistive load 40 V DC / 2 A resistive loadSwitching frequency < 10 Hz < 10 Hz < 10 Hz
Capacitive proximity sensors - function descriptionThe active component of a capacitiveproximity sensor consists of a disk-shapedsensor electrode and a cup shaped shield(fig. 1). These two electrodes form acapacitor with a base capacitance of CG.The capacitance changes by the amount∆C as a target approaches the sensor(distance~s).
The capacitor is part of an RC generator.It’s output voltage U~ is dependant on theeffective capacitance Ca = CG + ∆Cbetween the sensor electrode and theshield potential.
The RC generator starts to oscillate whenthe distance between the target and thecapacitor falls below a certain value. Theoutput voltage of the generator isdemodulated and filtered after which
background suppression is applied,producing the signal across the output.
This functional principle was furtherdeveloped by integrating the sensorelectrode in a multi-layer-board. In thismanner, the screening and theelectromagnetic compatability were
markedly improved. Thus, thisseries can be fitted directly tometal or connected to eachother. The applicability as “lookthrough” is simple to implementand can, together with thepossibility of fixing using cableconnectors, easily be used forflow monitoring in hoses &synthetic piping.
In capacitive proximity switches, therelative permittivity is the parameter forthe reduction factor. The following tablecontains some typical values for thereduction factor;
Operating principles and technology of ultrasonic sensorsUltrasonic sensors operate with apiezoelectric transducer as the soundemitter and receiver. A decoupling layer inspecial material is used to decouple theultrasonics to the air - an acousticallythin medium.
This ultrasonic transducer is embedded,watertight, into the sensor housing, inpolyeurothane foam.
The transducer transmits a packet of sonicpulses and converts the echo pulse into avoltage. The integrated controllercomputes the distance from the echo timeand the velocity of the sound. Thetransmitted pulse duration ∆t and thedecay time of the sonic transducer result inan unusable area in which the ultrasonicsensor cannot detect an object. Theutrasonic frequency lies between 65 kHzand 400 kHz, depending on the sensortype; the pulse repetition frequency isbetween 14 Hz and 140 Hz.
The active range of the ultrasonic sensor isreferred to as the sensing range Sd. Thisrange is bounded by the lowest andhighest sensing distances, whose valuesdepend on the characteristics of thetransducer. The highest sensing distance isgiven in the type code.
distance from the sensor S can be calulatedby D= 2 . tan α . S in a good approach.The angle α for a given distance S can betaken out of the charateristic responsecurves in the product data sheets. In theformula above, only the angle betweenthe curve and the centre-line (0º) has tobe inserted (half opening angle).For a simple evaluation of the sound conediameter D, you can use the list below,which shows the tan-values for anglesbetween α=2º and α=20º in 2º intervals.
The ultrasonic sensor detects objectswithin its sensing range, regardless ofwhether these objects approach thesensor axially or move through the soundcone laterally.
Ultrasonic sensors are available withswitching outputs and/or analogue outputs,various output functions are availableaccording to type.The ultrasonic beam has an opening angleof around ±5º. The sound pressure leveloutside this cone is less than half (-6 dB)that of the value on the sensor axis.
The opening angle defines the spatiallydimension for the sound cone. Thediameter of the sound cone D for a certain
Pepperl & Fuchs metal barrel sensorsAdjusting the switching pointsThe ultrasonic sensor features a switchoutput with two teachable switchingpoints. These are set by applying thesupply voltage -UB or +UB to theTEACH-IN input. The supply voltage mustbe applied to the TEACH-IN input for atleast 1s. LED’s indicate whether the sensorhas recognised the target during theTEACH-IN procedure. Switching point A1is taught with -UB, A2 with +UB.
Five different output functionscan be set1. Window mode, normally-open function2. Window mode, normally-closedfunction
3. One switching point, normally-openfunction
4. One switching point, normally-closedfunction
5. Detection of object presence
Electrical Connection- 4pin connector (pnp)
Electrical Connection- 5pin connector (npn)
Electrical Connection- 5pin connector (pnp)
M12 metal barrel sensors 30 to 400mm sensing range
M12 right angle 4-pin connector 2m PUR 464020 £5.67 £5.11
M12 right angle 4-pin connector 5m PUR 464050 £6.58 £5.93
M12 straight plug 4-pin No Cable 490011 £4.68 £4.22
M12 right angled plug 4-pin No Cable 490014 £4.83 £4.35
Common Features�Switch output�5 different outputs can be set�TEACH-IN input�Synchronisation options�Deactivation option�Temperature compensation� Insensitive to compressed air