General information for proximity sensors

The devices operate exactly likemechanical

switches, with the connected load beingswitched in

series. They can be used into PLC inputs like relays.

Noticeshould be taken on the influence of minimum

load current, leakage current and voltage drop.

In the "off" condition, only the leakage current(the no

load current) flows through the external load. In the

"on" condition the amplifiers' output transistor

conducts.

Between the connections of theproximity switch

there is now a voltage drop created by the internal Z-

diode(<6v) and this should be allowed for within the

supply voltage. The voltage applied to the external

load is lower than the supply voltage by an amount

equal to the voltage drop. The output amplifier is

short circuit proof andoverloadprotected.

DC 2 wire proximity switch

Series and paral lel connection of2 wire DC proximityswitches is not permitted.

Output circuit

load

BRN

BLU

Wiring diagram

LOADBRN

BLU

+(-)

-(+)

BRN

BLU

LOAD

-(+)

+(-)

N.O. N.C.

GENERAL INFORMATION FOR PROXIMITY SWITCHES

Specifications

Diameter

Item

Supply voltage

Ripple Vpp

M8

10-60 V DC

Output

Continous loadcurrent

Leakage current

Voltage drop(at Icont.)

Reverse polarity protection

Short-circuitprotection

Transientprotection

Switching frequency

Switchinghysteresis

Temperature drift

Repeat accuracy

Operating temperature

<10%

N.O. or N.C.

3-100mA

<1.2 mA

<8 V

Yes

Yes

Overload trippoint

2 kV, 1 mS, 1 kohm

1KHz

15%

10%

<2%

-25 -C to

o o+70 C

>120 mA

Shieldedshielded

1KHz 1KHz 500Hz 500Hz 200Hz

Non-Shielded

Non-shielded

M12 M18

ShieldedNon-shielded

M30 orQ-type

ShieldedNon-shielded

2KHz 2KHz

<0.8 mA

<6 V

+_

NAMUR - Sensors to DIN 19234

NAMUR-Sensors are polarized 2-wire-sensors which

change their internal resistance depending on the

distance to the target. They are designed for use

with external amplifiers, which convert the current

changes into a digital signal.

Connection diagram

Ri:1K

0V

+8.2VDC

NAMUR-sensor amplifier

W

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Nominal Operating Values

NAMUR-sensors operate with a supply voltage from5

to 25VDC. It is possible to work Directly into logic

circuits such as CMOS etc. Note: different operating

values(V,Ri) will co- unteract a change of the

switching distance. Within the admissible voltage

range it is ne-cessary to adopt the resistance Ri, as

well as the current in the switching point I(Sn). The

following table shows typical values:

V[VDC] Ri[k ] I(Sn)[mA] I[mA]

5

12

15

24

0.39

1.8

2.2

3.9

0.7

2.3

2.9

3.8

0.1

0.3

0.4

0.5

= =

=

=

= =

=

=

Application in EX-areas

If NAMUR-sensors are used in EX-Areasb following

table shows typical values: following table shows

typical values: (Explosion-hazardous areas) they

must be connected using approved switching

amplifiers with intrinsically safe control circuits. The

values of switching frequency and switching

hysteresis are based on inter connection by NAMUR-

amplifier.


Characteristic curve

I(mA)

4

3

2

1

1.55mA

1.75mA

S[mm]Sn

difference in

switchingcurrent

difference inswitching

I

S

Inductive Proximity Switches

When the electrically conductive material is removed

from the alternating field the oscillation amplitude

increaseswhich, by way of the electronic circuitry,

will restore the switch to the original unswitched

state.

Inductive Proximity Switches operate by using an L/C

resonant oscillator which generates, with the aid of a

coil located in the open pot core, a high frequency

alternating electromagnetic field. This field emerges

from the active face of the switch

When an electrically conductivematerial (for example

a steel plate) moves into the electro. Magnetic field,

an induced eddy current occurs. This eddy current

extracts energy from the L/Cresonant circuit in the

switch, and produces areduction in the oscillation

amplitude. This reduction in the amplitude is

converted by the associated electronic circuitry into

a clear electronic signal, and changes the state of the

switch.

H

SrFig. 1 Block Diagram - Inductive Switch

Normal Operating Distance

TheNormal Operating Distance is defined as the

distance between thedetector and the target when the

change (switching) in the logic state of the proximity

switch occurs. This distance and the tests associated

in obtaining this distance areoutline in CENELEC EN

50010 Standards. From this standard the target for

establishingNormal Operating Distance is an iron (Fe

37) square 1mm thick, and for cylindrical switches,

the size is as showen in Table 1. The normal sensing

distance Sn and Sr, Su, Sa information see Figure A.



Correction Factor

Inductive :When using inductive proximity switches

with non-ferrous metals it is nescessary to apply a

correction factor to the operating distance (sensing

range) as follows:

Brass

Aluminum

Copper

ChromeNickelAlloy

Stainless steel

Distance X. 0.50

X. 0.45

X. 0.40

X. 0.90

X. 0.85

Distance

Distance

Distance

Distance

Capacitive : Capacitive switches have an adjustable

detection range, and are dependent upon the type of

material to be sensed. See Figure 4.

MaterialsCuAlOtt.CrNiFe37

404555

85

Sn%

50

100

Fig. 4 Capacitive switch correction factor

Shielded & Nonshielded

Shielded construction includes a metal bandwhichsurrounds the ferrite core and coil arrangement. This

helps to direct the electro-magnetic field to the frontof the sensor.

Non shielded sensors do not have this metal band,therefore they can be side sensitive.

FERRITE

FERRITE

SHIELD SHIELD

Shielded Sensor

Nonshielded Sensor

Mounting

Because of possible interference of the

electromagnetic fields generated by the oscillators,

minimum spacing is required between adjacent or

opposing "active surfaces" of proximity switches.

The "active surface " may be flush with the metal in

which the switch is mounted, (see figure "Shielded

Mounting".) The"active surface"must have a free zone

in which no metal is present, (see figure "Non-shielded

Mounting".) When mounting proximity switches in this

manner where the "active surfaces" are opposite each

other, there must be a minimum distance between

them,(see figure "Opposite Mounting".)

It is good engineering practice tomount proximity

switches horizontally or with the active surface facing

down. Avoid proximity switches that face up wherever

possible, especially if metal filings and chips are

present.

3SnD

DD

Shielded Mounting

>



D

D

3Sn

2D

D D

Non-shielded Mounting

Opposite Mounting

>

>6Sn

The hysteresis is the travel of target between the

switch-on and the switch-off point. The switching

distance always relates to the switch-on point

curvestrigg er

switchproximity

Sdistanceswitching

hysteresisON point

OFF point

moving dir ection

Hysteresis

Hysteresis

Temperatre drift of sn

Switching frequency, maximum

The switching distance is specified for an ambienttemperature of 20 C. The following diagram gives theswitching distance as a function of ambienttemperature.

o

This frequency indicates the maximum number ofpulsesper second, this for an on/off ratio of 1:2 andat one half the nominalswitching distance sn

0 +20 +40 +60 +80-20C

Smm

r

Non conduc tingmaterial

s n/2

Proximityswitch

Standard ta rget

disc

Ripple content, maximum

Too much ripple content causes an undefinedswitching behaviour.Remedy: increase the smoothing capacitor or use astabilized power supply.

U

Ud

Ud

Uss

Uss

t

W = x 100(%)



IP 67

Degree of protection, accordingto DIN 40050/IEC529.Definition:

,

6

7

Protection against dust penetration. Fullprotection against shocks (electrical).Protection against water, when working undercertain conditions of time and pressure,plunged into water. The water doesn tpenetrate in sufficient quantity to causeDamage.Test conditions:Depth of immersion: 1mDuration: 30 min.

The items provided with protection IP 67 are nottherefore scheduled for working continuously inwater.

Tr

NPN

DC NPNoutput proximity switches consist ofthe following circuit. In N.O. operation, withnosensing,the transistor is in theOFF mode.When sensing, the load current passes throughthe transistor. In N.C. operation, the function isopposite. In N.O. operation, as the load currentpasses200mA (capacitive version over 300mA),the loadshort circuit protection is activated.

Remarks: Voltage drop <1V, it is tested in themax. load current, 200mA. Capacitive ProximitySwitch is tested in 300mA.

DC NPN output type

DC POWER

VOLTAGE DROP

SHORT CIRCUIT

PROTECTION

Tr

PNP

DC PNP output type

SHORT CIRCUITPROTECTION

DC POWER

VOLTAGE DROP

DC PNPoutput type proximity switches aredesigned with the following output circuit.In N.O. operation without sensing status, thetransistor is in the OFF mode, with sensing statusthe transistor is in the ON mode, as the loadcurrent passes through the transistor; in the N.C.mode, the operation is opposite in the N.O.Operation.

AS the loadcurrent passes 200mA(capacitiveproximity switch over 300mA), the load shortcircuit protection circuit is activated.

Remark: Voltage drop <1V is tested at the max.load current, 200mA. Capacitive Proximityswitches are tested at 300mA.

DC output type four wire

DC POWER

PNP

Tr2

DC POWER

NPN

Tr2

Tr1

Tr1

N.O., N.C. changeover 4 wire devices are shownin the following circuits A and B.When theproximity switch is in the sensingmodetransistor 1 is in theOFF mode; transistor 2 is inON mode. The max. load current is 200mA withshort circuit protection. Output terminal N.O.and N.C. may be connected to the load at thesame time.

A

B



AC output two wire device

AC ouput two wire proximity switches have outputcircuits with SCR. In the N.O. operation and non-sensing mode,the SCRappearsOFF, in the sensedmode the SCR is ON. Load current passes throughthe SCR and toform feed circuit with extend load.InN.C. operation, the operation is opposite the N.O.Operation.SCR in OFF mode, (itneeds by theoperation internal circuit for proximity switch). Thesmall current passing through the load is calledleakage current. When the SCR is in ONmodeinternal circuitof proximity switch operates) Thissmall voltage is called dropping voltage. The max.load current is 400 mA.

Leakage voltage is below 8V(load current is over20mA) leakagecurrent is below1.8mA.

SCR

LOAD

AC two wire output, N.O., N.C. changeable

AC twowire output, N.C./N.O. operation is

changeable, per the schematic below.Feedback

circuit as head is connected with terminal 3 and 4,

proximity switch is in N.O. Mode.As load is connected

with terminal 1 and 2, proximity switch is in N.C.

mode. As SCR is in OFF status, the internal circuit of

proximity switch the working needs the very small

current which is called leakage current.AsSCR is in

the status of ON, the internal operation of proximity

switch,the very small voltage available is called

dropping voltage.

4

3

2

1

SCR

LOAD

AC/DC outputs

These proximity switches are used as pilot devices

for AC-operated loads such as relays, contactors,

solenoids, etc.The solid state output permits the use

of the proximity switches directly on the line in series

with an appropriate load. They, therefore, replace

mechanical limit switches without alteration of

circuitry, where operating speedor environmental

conditions require the application of solid

stateproximity switches.

load

MOSFET

These proximity switches are typically available in a

voltage range of 20-250V AC or DC. All models are

available with either normally open(N.O.) normally

closed(N.C.), or with programmable outputs(from N.O.

to N.C.). Proximity switches with AC/DC outputs are

not recommended for use with 24V DC programmable

controller inputs.

The max. load current is 400 mA.Dropping voltagebelow 8V(load current over 20mA),leakage current is below1.8mA.N.O., N.C. operation are not available at the sametime.It isonly available for N.O. orN.C.

Leakage current

Load impedance

The leakage current is the currentwhich passesthrough the output transistor when it is blocked (thismust be kept into account, especially in the case ofparallel connection of several switches).

Instead of a maximum output current, a minimum loadimpedance may be specified.Aminimum load of 120 Ohms e.g. Translates into amaximumoutputcurrent of 100mAat 12V or 200mAat24V. On the other hand. If the maximum output currentis 200mA, the lowest acceptable load impedance at

24V is 120 Ohms.



Parallel connection

Series connection

NPN

PNP

NPN

PNP

NPN

PNP

NPN

PNP

NPN

PNP

NPN

PNP

NPN

PNP

NPN

PNP

1

1

1

1

2

2

2

2

n-1

n-1

n-1

n-1

n

n

n

n

+U

+U

+U

+U

0V

0 V

0V

0V

BL K

BR N

BL U

B LK

B RN

B LU

B LK

BLK

B RN

BRN

B LU

BLU

BL K

BR N

BL U

B LK

B RN

B LU

B LK

BLK

B RN

BRN

B LU

BLU

BL K

BR N

BL U

B LK

B RN

B LU

B LK

BLK

B RN

BRN

B LU

BLU

BL K

BR N

BL U

B LK

B RN

B LU

B LK

BLK

B RN

BRN

B LU

BLU

Parallel-connection:N.O. Sensors: OR function(any one sensor or all

made: load on )N.C. Sensors: NAND Function(all sensors open: load

off )

,,,,

,,,,

Series-connection:N.O. Sensors: AND Function( made: load

on )N.C. Sensors: NOR Function( open:

load off )

all sensors

any one sensor

,,,,

,,,,

Short circuit protection

Tightening torque, maximum

Pulsing short circuit protection

In case of overloador shortcircuit, the output tran-sistor is rapidly switched on and off. This testswhether the short has been removedor not.This kindofproximity switch's voltage drop is <1V.

+

-

OUTPUT

shortcircuitprotection

I

A very large driving force on the nut, destroys theswitchmechanically. The following tighteningtorques should not be exceeded:

M4x0.5 0.8Nm

M5x0.5 1.5Nm

M8 1x 4 Nm

M12x1 10 Nm

M18x1 25 Nm

M30x1.5 70 Nm


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General information for proximity sensors