1479 INDUCTIVE PROXIMITY SENSORS

Transcription

1 179 INDUCTIVE PROXIMITY SENSORS INTRODUCTION Principles of opertion A proximity sensor detects the pproch of n object without mking contct. There re three types of proximity sensors: 1) High-frequency oscilltion type using electromgnetic induction ) Mgnetic type using mgnetism 3) cpcity type which senses the chnges in the electrosttic cpcity between the sensing object nd the sensor. High-frequency oscilltion type Principle of high-frequency oscilltion type inductive proximity sensor The detection coil locted t the front end of the sensor produces high-frequency mgnetic field s shown in the figure below. When n object (metllic) pproches this mgnetic field, induced currents flow in the metl, cusing therml loss nd resulting in the reduction or stopping of oscilltions. This chnge in stte is detected by n oscilltion stte sensing circuit which then opertes the output circuit. High-frequency mgnetic field Using mgnetic field Proximity sensor Using electric field Mgnetic type cpcity type (metl) Eddy currents generte energy (therml) loss due to the resistnce of the metl, reducing the mplitude of oscilltion. Pnsonic Industril Devices SUNX proximity sensors re highfrequency oscilltion type inductive proximity sensors. Eddy current Opertion indictor Sensing direction Oscilltion circuit Oscilltion stte sensing circuit circuit FEATURES Flow Proximity Non-contct detection Unlike limit switch, it detects n object without ny mechnicl contct. Hence, there is no likelihood of the sensing object or the sensor getting dmged by contct. Usble in severe environment Relible sensing is possible even in dverse conditions where it cn come in contct with wter, etc. Most of the sensors hve IP67 protection nd oil resistnt construction. High precision It is suitble for precise object positioning becuse of its very high repetbility. Short response time Stble detection is possible even with fst trveling objects becuse of its high response frequency (3.3 khz mx.). Long life Due to its non-contct output, it hs long life nd requires prcticlly no mintennce. * However, it lso hs the following disdvntges. Only metl detection It cnnot detect non-metls in which current cnnot flow, since detection is bsed on therml loss due to induced current. Also, metls such s ferrite, which do not llow current flow, cnnot be detected. Short sensing rnge Although there re severl methods for improving the sensing rnge, such s incresing the detection coil size, using non-shielded sensor heds, etc., the sensing rnge is still smller thn tht of photoelectric sensors.

2 INDUCTIVE PROXIMITY SENSORS 180 TYPES OF SENSORS Method of clssifiction 1 Clssifiction by structure This clssifiction is bsed on whether the constituent circuit elements re built-in or seprted. It is useful for selecting sensors in view of the mounting spce, power supply, nd noise immunity. proximity sensor High-frequency oscilltion type Amplifier built-in Amplifier-seprted Clssifiction 1 Clssifiction by structure Type Amplifier built-in Outline nd Fetures As the mplifier is built-in, non-contct output is obtined simply by connecting DC electric power supply. It hs high noise immunity becuse the mplifier is builtin. Amplifier circuit DC electric power supply Non-contct output Clssifiction by coil enclosure This clssifiction is bsed on the structure surrounding the sensor hed (detection coil). It is useful for selecting sensors in view of the mounting style, sensing rnge, influence of surroundings, etc. proximity sensor High-frequency oscilltion type Shielded Non-shielded Amplifier-seprted The sensing portion cn be mde smll since the detection coil is seprted s the sensor hed. However, its noise immunity is less thn tht of the mplifier built-in type. The sensitivity setting cn be done on the mplifier t remote plce. hed Amplifier Amplifier circuit DC electric power supply 3 Clssifiction by output circuit This clssifiction is bsed on the type of output circuit nd the output voltge. This clssifiction is useful to select sensors ccording to the input conditions of the device or equipment connected to the sensor output. NPN open-collector trnsistor Non-contct output proximity sensor High-frequency oscilltion type ON / OFF output Anlog output PNP open-collector trnsistor DC -wire Anlog voltge Anlog current Flow Proximity

3 181 INDUCTIVE PROXIMITY SENSORS TYPES OF SENSORS Clssifiction by coil enclosure Type Outline nd Fetures Shielded A metl enclosure shields the sides of the detection coil. The sensor cn be embedded in metl s it is less ffected by the surrounding metl. GX-3S, GX-S, GX-5S nd GX-5SU require smll clernce t the front sensor end. hed Metl Metl enclosure Non-shielded The sides of the detection coil re not shielded by metl enclosure. [All resin-enclosed sensors (GX-F/H series, GXL series, GL series) re non-shielded types.] They hve longer sensing rnge thn shielded type of the sme size. Since it is esily ffected by surrounding metl, cre should be tken tht metl other thn the sensing object does not come ner the sensor front end. Metl enclosure 3 Clssifiction by output circuit Type Outline nd Fetures Type Outline nd Fetures Able to drive rely, PLC, TTL logic circuit, etc. A seprte power supply cn be used for the lod. Long life High-speed response Commonly used in North Americ or Jpn Wire sving Low current consumption Long life High-speed response Limittion on connectble lod Flow Proximity ON / OFF output NPN open-collector trnsistor PNP open-collector trnsistor D Internl circuit V Lod Symbols... D : Reverse supply polrity protection diode : Surge bsorption zener diode (Its position differs with the model.) : NPN output trnsistor Commonly used output circuit in Europe Power supply is not required for the lod. Long life High-speed response D Internl circuit V Lod Symbols... D : Reverse supply polrity protection diode (Its position differs with the model.) : Surge bsorption zener diode (Its position differs with the model.) : PNP output trnsistor DC power supply DC power supply ON / OFF output DC -wire Internl circuit Bleeder resistnce Lod Lod Symbols... : Surge bsorption zener diode : PNP output trnsistor DC power supply

4 INDUCTIVE PROXIMITY SENSORS 18 GLOSSARY Term Mximum opertion distnce Stble sensing rnge It is the distnce to the point t which the sensor first detects the stndrd sensing object s it slowly pproches the sensing hed s shown in the figure below. Exmple: In cse of GX-1MU Stndrd sensing object (Iron sheet t 1 mm t in) Point t which the sensor first turns ON. Mximum opertion distnce 3 mm in ±10 % The mximum opertion distnce rnges from to 3.3 mm in due to product vrition. It is the sensing rnge for which the sensor cn stbly detect the stndrd sensing object even if there is n mbient temperture drift nd/or supply voltge fluctution. Normlly, it is 70 to 80 % of the mximum opertion distnce. Exmple: In cse of GX-1MU Stndrd sensing object (Iron sheet t 1 mm t in) Term Hysteresis For sensor, the hysteresis is the difference between the opertion distnce, when the first ction is tken with the stndrd sensing object pproching long the sensing xis, nd the resumption distnce, when the first ction is tken with the stndrd sensing object receding. It is expressed s percentge of the opertion distnce. Normlly, hysteresis of 10 to 0 % of the mximum opertion distnce is incorported to prevent chttering of the output due to vibrtion, etc., of the sensing object. Resumption distnce Hysteresis Opertion distnce Sensing xis Mximum opertion distnce Vrition in the sensor opertion point when sensing is repetedly done under constnt conditions. Repetbility perpendiculr to sensing xis Repetbility Sensing xis Stndrd sensing object Use in the stble sensing rnge (0 to. mm 0.09 in). It is the smllest size object for which the sensing rnge becomes constnt. The sensing rnge, hysteresis, etc., re ll specified for the stndrd sensing object. The mteril of the stndrd sensing object is iron. Reference for the size of the stndrd sensing object ( mm in) Shielded type: Approx. equl to the size (b) of the sensing portion. Non-shielded type: Approx. equl to 1.5 times the size (b) of the sensing portion. Correltion between sensing object size nd sensing rnge Snesing rnge L (mm in) mm in t 1 mm t in L proximity sensor ø b Iron Stinless steel (SUS30) side length (mm in) Brss Aluminum (Metl sheet, 1 mm in thick) L Mximum response frequency Sensing rnge vrition temperture chrcteristics Sensing rnge vrition voltge chrcteristics Repetbility long sensing xis As shown in the figure below, rotting plte hving the stndrd sensing object psted t constnt intervls is plced in front of the proximity sensor. The plte is rotted while observing the sensing output. The mximum number of times per second t which sensing cn be done, for which the corresponding sensing output cn be obtined, is the mximum response frequency. Stndrd sensing object proximity sensor 50 % of mximum opertion distnce : Side length of stndrd sensing object It is the chnge in the sensing rnge, with respect to the sensing rnge t 0 C 68 F mbient temperture, when the mbient temperture is vried over the rted mbient temperture rnge. Exmple: In cse of GX-U/N series Sensing rnge vrition (%) Within ±10 % of sensing rnge t 0 C 68 F 70 C 158 F 5 C 13 F 0 C 68 F It is the chnge in the sensing rnge with respect to the sensing rnge t prticulr supply voltge when the supply voltge vries by ±10 %. Flow Proximity

5 183 INDUCTIVE PROXIMITY SENSORS GLOSSARY Term Degree of protection ginst wter, humn body nd solid foreign mteril. Protection degree is specified s per IEC (Interntionl Electrotechnicl Commission). IEC stndrd IP Second figure... Protection ginst wter penetrtion First figure Protection ginst humn body nd solid foreign mteril Protection degree specified by the first figure First figure Protection degree specified by the second figure Second figure 0 No protection 0 No protection 1 Protection ginst contct with internl live prts by humn hnd (ø50 mm ø1.969 in) ø50 ø No hrmful effect due to verticlly flling wter drops Protection ginst contct with internl live prts by humn finger (ø1 mm ø0.7 in) ø1 ø0.7 No hrmful effect due to wter drops flling from rnge 15 wider thn the verticl Protection ginst contct with internl live prts by solid object more thn.5 mm in in thickness or dimeter t.5 t No hrmful effect due to wter drops flling from rnge 60 wider thn the verticl Protection Protection ginst contct with internl live prts by solid object more thn 1.0 mm in in thickness or dimeter t 1.0 t No hrmful effect due to wter splshes from ny direction 5 Protection ginst dust penetrtion which cn ffect opertion 5 No hrmful effect due to direct wter jet from ny direction 6 Complete protection ginst dust penetrtion 6 No wter penetrtion due to direct wter jet from ny direction Note: The IEC stndrd prescribes test procedures for ech protection degree given bove. The protection degree specified in the product specifictions hs been decided ccording to these tests. 7 8 No wter penetrtion due to immersion in wter under specified conditions No wter penetrtion during immersion, even under conditions tht re more hrsh thn the ones in No.7 Flow Proximity Cution Although the protection degree is specified for the sensor including the cble, the cble end is not wterproof, nd is not covered by the protection specified. Hence, mke sure tht wter does not seep in from the cble end. Wter should not seep in from here IP67G / IP68G This specifies protection ginst oil in ddition to IP67 / IP68 protection of IEC stndrds. It specifies tht oil drops or bubbles should not enter from ny direction.

6 INDUCTIVE PROXIMITY SENSORS 18 GLOSSARY Term Sensing field The curves re plotted s series of operting points t which the sensor detects the stndrd sensing object s it pproches from the left or the right for different setting distnces (with the sensitivity djuster t mximum sensitivity). The grph is useful to determine the mounting position of the sensor with respect to the sensing object. The grph shows typicl chrcteristics. There could be slight vrition depending on the product. Exmple: In cse of GXL-15 (Stndrd) type Setting distnce L (mm in) Left Center Right Operting point l (mm in) Stndrd sensing object l L Correltion between sensing object size nd sensing rnge The grph shows the correltion between sensing object size nd sensing rnge. For sensors hving sensitivity djuster, the grph is shown for the condition when the sensitivity djuster is set such tht the stndrd sensing object is just detectble t the mximum sensing distnce. The grph is useful to determine the sensing distnce for which the sensor cn stbly detect n object considering its size. The grph shows typicl chrcteristics. There could be slight vrition depending on the product. Exmple: In cse of GXL-15 (Stndrd) type Sensing rnge L (mm in) Iron side length (mm in) mm in t 1 mm L t in Flow Proximity

7 185 INDUCTIVE PROXIMITY SENSORS PRECAUTIONS FOR PROPER USE Setting distnce Approch perpendiculr to sensing xis Normlly the sensor is used with the sensing object pproching from direction perpendiculr to the sensing xis. Adjust the distnce to the sensing object to be within the stble sensing rnge which is slightly less thn the mximum opertion distnce. Approch perpendiculr to sensing xis Stble sensing rnge Sensing xis Approch long sensing xis When the sensing object pproches the sensor long the sensing xis, it is detected t the mximum opertion distnce. However, mke sure to void ny collision between the sensing object nd the sensor, which my occur due to the sensing object speed. Mounting Influence of surrounding metl Surrounding metl my ffect the performnce of the inductive proximity sensor. Keep the specified distnce between the surrounding metl nd the sensor. For detils, refer to the section PRECAUTIONS FOR PROPER USE of ech sensor. <Cylindricl type nd threded (shielded) type> Bewre of bckground metl Bckground metl <Threded (non-shielded) type> Bewre of bckground nd surrounding metl Bckground metl <Top sensing (non-shielded) type> Bewre of bckground nd side metl c b Surrounding metl Approch long sensing xis Sensing xis Type of metl objects nd sensing rnge The sensing rnge is specified for the stndrd sensing object. If the sensing object is smller, or is non-ferrous, the sensing rnge shortens. Correltion between sensing object size nd sensing rnge (In cse of GXL-8 type) Bckground metl c Side metl b <Front sensing (non-shielded) type> Bewre of bckground nd side metl Side metl d d Bckground metl Side metl c b c Flow Proximity Snesing rnge L (mm in) mm in t 1 mm L t in Front sensing Iron Stinless steel (SUS30) Brss Aluminum mm in t 1 mm L t in Top sensing side length (mm in) Correction coefficient for different sensing object mterils (In cse of GXL-8 type) Correction coefficient Iron 1 Stinless steel (SUS30) Brss Aluminum 0.8 pprox pprox pprox. Note: The sensing rnge lso chnges if the sensing object is plted. Mutul interference When severl inductive proximity sensors re mounted close together, the high frequency mgnetic field emnting from one sensor exerts n electromgnetic influence on the other sensors, mutully cusing their opertion to become unstble (clled mutul interference). In this cse, the following countermesures re necessry. Countermesures 1 : Keep sufficient spcing. Fce to fce mounting A B Prllel mounting For detils, refer to the section PRECAUTIONS FOR PROPER USE of ech sensor. Countermesures : When used long with different frequency type (I type), in which the oscilltion frequency is different, two sensors cn be prllely mounted next to ech other. GXL-8F GXL-8FI Different frequency type sensor (I type)

8 INDUCTIVE PROXIMITY SENSORS 186 PRECAUTIONS FOR PROPER USE Bleeder resistnce setting procedures The DC -wire type inductive proximity sensors mnufctured by Pnsonic Industril Devices SUNX do not normlly function in the cse where the lod current is under 3 ma when the lod is connected to the output. In tht cse, it is necessry for lod current of 3 ma or more to flow by connecting the lod to the resistnce in prllel. This resistnce is clled bleeder resistnce. The I/O circuit digrm of the DC -wire type inductive proximity sensors is described s below. I/O circuit of DC- wire type Exmine the necessity for bleeder resistnce Color code First, exmine if bleeder resistnce is necessry when Bleeder resistnce connecting the lod to the output. Internl circuit (Brown) 3 to 70 ma in ON stte (Note) 0.8 ma in OFF stte 3 V in ON stte (Blue) Lod Lod Symbols : Surge bsorption zener diode : PNP output trnsistor Note: The mximum lod current vries depending on the mbient temperture. 1 to V DC ±10 % 3 V in ON stte R I V Provided tht lod is R, lod current is I, supply voltge is V, nd output residul voltge is 3 V, you cn clculte the lod current I when output is in the ON stte using the following formul. V 3 [V] I = [ma] R [kω] The DC -wire type inductive proximity sensors mnufctured by Pnsonic Industril Devices SUNX do not need bleeder resistnce when I 3 ma, but need it when I < 3 ma. Conditions for the lod 1) The lod should not be ctuted by the lekge current (0.8 ma) in the OFF stte. ) The lod should be ctuted by (supply voltge 3 V) in the ON stte. 3) The current in the ON stte should be between 3 to 70 ma DC. In cse the current is less thn 3 ma, connect bleeder resistnce in prllel to the lod so tht current of 3 ma, or more, flows. Clcultion method of the necessry bleeder resistnce 3 V in ON stte I Vb Ib Rb R IR V Provided tht bleeder resistnce is Rb, electric current flowing to Rb is Ib, voltge within Rb is Vb, electric current flowing to R is IR, lod current to the sensor is I, nd supply voltge is V ; I = IR Ib = 3 [ma] or more Vb = Rb Ib = R IR = V 3 [V] the reltionl expression bove is formulted. The bleeder resistnce Rb nd bleeder resistnce power Pb cn be clculted using the formul below. Vb V 3 [V] Rb = = = Ib I IR [ma] Pb = Vb Ib Vb [V] = = Rb [kω] Pb = V 3 [V] 3 IR [ma] (V 3) [V] Rb 1000 [Ω] V [V] Rb 1000 [Ω] [kω] or less [W] or more Simplifies to [W] or more * In ctulity, select wttge tht is few times greter thn Pb. Bleeder resistnce tht is necessry for the DC -wire type Color code Internl circuit (Brown) (Blue) Bleeder resistnce Rb 3 to 70 ma in ON stte 0.8 ma in OFF stte 3 V in ON stte Lod Lod 1 to V DC ±10 % In the cse tht lod current is under 3 ma when the output is in the ON stte The bleeder resistnce Rb nd bleeder resistnce power Pb cn be clculted using the formul below. Rb Pb Supply voltge 3 [V] 3 Lod current [ma] > (Supply voltge) [V] Rb 1000 [Ω] [kω] [W] * In ctulity, select wttge tht is few times greter thn Pb. Flow Proximity

9 187 INDUCTIVE PROXIMITY SENSORS PRECAUTIONS FOR PROPER USE Other precutions Our products hve been developed / produced for industril use only. Although the protection degree is specified for the sensor including the cble, the cble end is not wterproof nd is not covered by the protection specified. Hence, mke sure tht wter does not seep in from the cble end. Wter should not seep in from here Using wireless devices round sensors nd wires my cuse mlfunction. So mke sure not to pproch those. Tke cre tht the sensor does not come in direct contct with orgnic solvents, such s, thinner, etc. Mke sure tht the sensing end is not covered with metl dust, scrp or sptter. It will result in mlfunction. Flow Proximity Mke sure tht the power supply is off while wiring. Verify tht the supply voltge vrition is within the rting. If power is supplied from commercil switching regultor, ensure tht the frme ground (F.G.) terminl of the power supply is connected to n ctul ground. AC F.G. Ground Switching regultor If using electromgnetic vlves, mgnet switches, motors, etc. simultneously in your system, control surges with surge killer. Not doing so will cuse chttering nd other mlfunctions. In cse noise generting equipment (switching regultor, inverter motor, etc.) is used in the vicinity of this product, connect the frme ground (F.G.) terminl of the equipment to n ctul ground. Do not run the wires together with high-voltge lines or power lines or put them in the sme rcewy. This cn cuse mlfunction due to induction. High-voltge line or power line These sensors re only for indoor use. Mke sure tht stress by forcible bend or pulling is not pplied directly to the sensor cble joint. The usge environment should be within the rnges described in the specifictions. Use sensors within the rnge shown in the white prt of the mbient temperture / humidity grph below nd lso within the certified mbient temperture nd humidity rnge of ech product. When using sensors within the rnge shown in the digonl line shded prt of the grph, there is possibility tht condenstion my occur depending on chnges in the mbient temperture. Plese be creful not to let this hppen. Furthermore, py ttention tht freezing does not occur when using below 0 C 3 F. Plese void condenstion nd freezing when storing the product s well. Ambient humidity (% RH) Metl dust / scrp The sptter-resistnt type GX-F U-J, GH-F8SE prevents sticking of sptter due to its fluorine resin coting. Avoid condenstion. Be creful bout freezing when using below 0 C 3 F Ambient temperture ( C F)