GENERAL INFORMATION FOR PROXIMITY SWITCHES

Transcription

1 78 C wire proximity switch The devices operate exactly like mechaical switches, with the coected load beig switched i series. They ca be used ito PLC iputs like relays. Notice should be take o the ifluece of miimum load curret, leakage curret ad voltage drop. Output circuit load I the "off" coditio, oly the leakage curret(the o load curret) flows through the exteral load. I the "o" coditio the amplifiers' output trasistor coducts. Betwee the coectios of the proximity switch there is ow a voltage drop created by the iteral Z- diode(<6v) ad this should be allowed for withi the supply voltage. The voltage applied to the exteral load is lower tha the supply voltage by a amout equal to the voltage drop. The output amplifier is short circuit proof ad overload protected. Wirig diagram N.O. LOA +(-) -(+) N.C. +(-) LOA -(+) Item Specificatios Supply voltage Ripple Vpp Output iameter Cotious load curret Leakage curret Voltagedrop(at Icot.) M V C <0% N.O. or N.C ma <. ma <8 V M M8 M30 or Q-type No- Shielded Shielded Noshielded shielded Shielded Noshielded Shielded Noshielded <0.8 ma <6 V Series ad parallel coectio of wire C proximityswitches is ot permitted. NAMUR - Sesors to IN 934 NAMUR-Sesors are polarized -wire-sesors which chage their iteral resistace depedig o the distace to the target. They are desiged for use with exteral amplifiers, which covert the curret chages ito a digital sigal. Reverse polarity protectio Short-circuit protectio Overload trip poit Trasiet protectio Yes Yes >0 ma kv, ms, kohm Coectio diagram NAMUR-sesor amplifier Switchig frequecy KHz KHz KHz KHz KHz 500Hz 500Hz 00Hz +8.VC Switchig hysteresis 5% Temperature drift +_ 0% Repeat accuracy <% Operatig temperature o -5 C t o o + 70 C Ri:K W

2 79 Characteristic curve I(mA) 4 Iductive Proximity Switches Iductive Proximity Switches operate by usig a L/C resoat oscillator which geerates, with the aid of a coil located i the ope pot core, a high frequecy alteratig electromagetic field. This field emerges from the active face of the switch 3 H Nomial Operatig Values NAMUR-sesors operate with a supply voltage from 5 to 5VC. It is possible to work irectly ito logic circuits such as CMOS etc. Note: differet operatig values(v,ri) will co- uteract a chage of the switchig distace. Withi the admissible voltage rage it is e-cessary to adopt the resistace Ri, as well as the curret i the switchig poit I(S). The followig table shows typical values: Applicatio i EX-areas If NAMUR-sesors are used i EX-Areasb followig table shows typical values: followig table shows typical values: (Explosio-hazardous areas) they must be coected usig approved switchig amplifiers with itrisically safe cotrol circuits. The values of switchig frequecy ad switchig hysteresis are based o iter coectio by NAMURamplifier. V[VC] Ri[k ] I(S)[mA] I[mA] mA.55mA S differece i switchigcurret differece i switchig = 0.7 = 0. =.3 =.9 S S[mm] I = 0.3 = 0.4 Sr Fig. Block iagram - I ductive Switch Whe a electrically coductive material (for example a steel plate) moves ito the electro. Magetic field, a iduced eddy curret occurs. This eddy curret extracts eergy from the L/Cresoat circuit i the switch, ad produces a reductio i the oscillatio amplitude. This reductio i the amplitude is coverted by the associated electroic circuitry ito a clear electroic sigal, ad chages the state of the switch. Whe the electrically coductive material is removed from the alteratig field the oscillatio amplitude icreases which, by way of the electroic circuitry, will restore the switch to the origial uswitched state. Normal Operatig istace The Normal Operatig istace is defied as the distace betwee the detector ad the target whe the chage (switchig) i the logic state of the proximity switch occurs. This distace ad the tests associated i obtaiig this distace are outlie i CENELEC EN 5000 Stadards. From this stadard the target for establishig Normal Operatig istace is a iro (Fe 37) square mm thick, ad for cylidrical switches, the size is as showe i Table. The ormal sesig distace S ad Sr, Su, Sa iformatio see Figure A = 3.8 = 0.5

3 80 Correctio Factor Noshielded Sesor Iductive : Whe usig iductive proximity switches with o-ferrous metals it is escessary to apply a correctio factor to the operatig distace (sesig rage) as follows: Brass Alumium Copper Chrome Nickel Alloy Stailess steel istace X istace istace istace istace X X X X FERRITE Capacitive : Capacitive switches have a adjustable detectio rage, ad are depedet upo the type of material to be sesed. See Figure 4. Moutig Because of possible iterferece of the electromagetic fields geerated by the oscillators, miimum spacig is required betwee adjacet or opposig "active surfaces" of proximity switches. S% Fe37 CrNi Ott. Al Cu Materials Fig. 4 Capacitive switch correctio factor Shielded & Noshielded The "active surface " may be flush with the metal i which the switch is mouted, (see figure "Shielded Moutig".) The "active surface" must have a free zoe i which o metal is preset, (see figure "No-shielded Moutig".) Whe moutig proximity switches i this maer where the "active surfaces" are opposite each other, there must be a miimum distace betwee them,(see figure "Opposite Moutig".) It is good egieerig practice to mout proximity switches horizotally or with the active surface facig dow. Avoid proximity switches that face up wherever possible, especially if metal filigs ad chips are preset. Shielded costructio icludes a metal bad which surrouds the ferrite core ad coil arragemet. This helps to direct the electro-magetic field to the frot of the sesor. No shielded sesors do ot have this metal bad, therefore they ca be side sesitive. Shielded Moutig > 3S Shielded Sesor SHIEL SHIEL FERRITE

4 8 No-shielded Moutig Switchig frequecy, maximum This frequecy idicates the maximum umber of pulses per secod, this for a o/off ratio of : ad at oe half the omial switchig distace s > 3S Sta dard ta rget Pro ximity switch s / Opposite Moutig No coduc tig material disc Temperatre drift of s >6S The switchig distace is specified for a ambiet o temperature of 0 C. The followig diagram gives the switchig distace as a fuctio of ambiet temperature. Sr mm Hysteresis The hysteresis is the travel of target betwee the switch-o ad the switch-off poit. The switchig distace always relates to the switch-o poit C Ripple cotet, maximum movig dir ectio U OFF poit ON poit hysteresis Ud Uss switc hig distace S trigg er curves proximity switch t Hysteresis Us s W = x 00(%) U d Too much ripple cotet causes a udefied switchig behaviour. Remedy: icrease the smoothig capacitor or use a stabilized power supply.

5 8 IP 67 egree of protectio, accordig to IN 40050/IEC59. efiitio: 6 7 Protectio agaist dust peetratio. Full protectio agaist shocks (electrical). Protectio agaist water, whe workig uder certai coditios of time ad pressure,, pluged ito water. The water does t peetrate i sufficiet quatity to cause amage. Test coditios: epth of immersio: m uratio: 30 mi. The items provided with protectio IP 67 are ot therefore scheduled for workig cotiuously i water. AS the load curret passes 00mA(capacitive proximity switch over 300mA), the load short circuit protectio circuit is activated. Remark: Voltage drop <V is tested at the max. load curret, 00mA. Capacitive Proximity switches are tested at 300mA. SHORT CIRCUIT PROTECTION Tr VOLTAGE ROP C POWER C output type C output proximity switches cosist of the followig circuit. I N.O. operatio, with osesig,the trasistor is i the OFF mode. Whe sesig, the load curret passes through the trasistor. I N.C. operatio, the fuctio is opposite. I N.O. operatio, as the load curret passes 00mA (capacitive versio over 300mA), the load short circuit protectio is activated. Remarks: Voltage drop <V, it is tested i the max. load curret, 00mA. Capacitive Proximity Switch is tested i 300mA. C output type four wire N.O., N.C. chageover 4 wire devices are show i the followig circuits A ad B.Whe the proximity switch is i the sesig mode trasistor is i the OFF mode; trasistor is i ON mode. The max. load curret is 00mA with short circuit protectio. Output termial N.O. ad N.C. may be coected to the load at the same time. Tr C POWER Tr Tr C POWER SHORT CIRCUIT PRO TECTIO N VOLTA GE ROP A C output type C output type proximity switches are desiged with the followig output circuit. I N.O. operatio without sesig status, the trasistor is i the OFF mode, with sesig status the trasistor is i the ON mode, as the load curret passes through the trasistor; i the N.C. mode, the operatio is opposite i the N.O. Operatio. Tr Tr C POWER B

6 83 AC output two wire device AC ouput two wire proximity switches have output circuits with SCR. I the N.O. operatio ad osesig mode,the SCR appears OFF, i the sesed mode the SCR is ON. Load curret passes through the SCR ad to form feed circuit with exted load.i N.C. operatio, the operatio is opposite the N.O. Operatio.SCR i OFF mode, (it eeds by the operatio iteral circuit for proximity switch). The small curret passig through the load is called leakage curret. Whe the SCR is i ON mode iteral circuit of proximity switch operates) This small voltage is called droppig voltage. The max. load curret is 400 ma. AC/C outputs These proximity switches are used as pilot devices for AC-operated loads such as relays, cotactors, soleoids, etc. The solid state output permits the use of the proximity switches directly o the lie i series with a appropriate load. They, therefore, replace mechaical limit switches without alteratio of circuitry, where operatig speed or evirometal coditios require the applicatio of solid stateproximity switches. Leakage voltage is below 8V(load curret is over 0mA) leakage curret is below.8ma. LOA SC R MOSFET loa d AC two wire output, N.O., N.C. chageable AC two wire output, N.C./N.O. operatio is chageable, per the schematic below.feedback circuit as head is coected with termial 3 ad 4, proximity switch is i N.O. Mode.As load is coected with termial ad, proximity switch is i N.C. mode. As SCR is i OFF status, the iteral circuit of proximity switch the workig eeds the very small curret which is called leakage curret.as SCR is i the status of ON, the iteral operatio of proximity switch,the very small voltage available is called droppig voltage. SCR 3 4 LOA The max. load curret is 400 ma. roppig voltage below 8V(load curret over 0mA), leakage curret is below.8ma. N.O., N.C. operatio are ot available at the same time.it is oly available for N.O. or N.C. These proximity switches are typically available i a voltage rage of 0-5 AC or C. All models are available with either ormally ope(n.o.) ormally closed(n.c.), or with programmable outputs(from N.O. to N.C.). Proximity switches with AC/C outputs are ot recommeded for use with 4V C programmable cotroller iputs. Leakage curret The leakage curret is the curret which passes through the output trasistor whe it is blocked (this must be kept ito accout, especially i the case of parallel coectio of several switches). Load impedace Istead of a maximum output curret, a miimum load impedace may be specified. Amiimum load of 0 Ohms e.g. Traslates ito a maximum output curret of 00mA at V or 00mA at 4V. O the other had. If the maximum output curret is 00mA, the lowest acceptable load impedace at 4V is 0 Ohms.

7 84 Parallel coectio +U +U V + U Series-coectio: N.O. Sesors: AN Fuctio( all sesors made: load o ) N.C. Sesors: NOR Fuctio( ay oe sesor ope: load off ) Short circuit protectio Pulsig short circuit protectio I case of overload or short circuit, the output trasistor is rapidly switched o ad off. This tests whether the short has bee removed or ot.this kid of proximity switch's voltage drop is <V. Parallel-coectio: N.O. Sesors: OR fuctio(ay oe sesor or all made: load o ) N.C. Sesors: NAN Fuctio(all sesors ope: load off ) Series coectio short circuit protectio I Tighteig torque, maximum + - OUT PUT + U A very large drivig force o the ut, destroys the switch mechaically. The followig tighteig torques should ot be exceeded: M4x Nm M5x0.5.5 Nm - M8x Mx M8x 4 Nm 0 Nm 5 Nm M30x.5 70 Nm