Training manual Inductive Sensors º´«·¼ •»²•±®• ¿²¼ ¼·¿¹²±•¬·½ •§•¬»³• °±•·¬·±² •»²•±®• ¿²¼ ±¾¶»½¬ ®»½±¹²·¬·±² ¾«•ô ·¼»²¬·º·½¿¬·±² ¿²¼ ½±²¬®±´ •§•¬»³• 1 Training manual You will find further information, data sheets, prices etc. at: www.ifm-electronic.com Training manual Inductive proximity switches (March 2003) C:\lokal\s100e.doc10.01.07 11:55 Guarantee note This manual was written with the utmost care. However, we cannot assume any guarantee for the contents. Since errors cannot be avoided despite all efforts we appreciate your comments. We reserve the right to make technical alterations to the products so that the contents of the training manual may differ in this respect. 2 Induticve Sensors Contents 1 Introduction 5 1.1Proximity switches in industrial processes5 1.2Notation7 1.3On the contents7 2Basics 9 2.1Electromagnetic induction9 3Features of inductive proximity switches12 3.1Comparison12 3.1.1Limitation12 3.1.2Mechanical and electronic switches13 3.2Technology and operating principle15 3.2.1Basic inductive sensor15 3.2.2Signal generation19 3.2.3Evaluation21 3.3Practical use23 3.3.1Operating distance23 3.3.2Hysteresis28 3.3.3Correction factors30 3.3.4Switching times and switching frequency34 3.3.5Notes on practical use39 3.4Mounting instructions41 3.4.1Flush / Non flush41 3.4.2Mutual interference44 3.4.3Mechanical stability46 3.5Technology and operating principle K1, K048 3.5.1Designations48 3.5.2Conventional inductive sensor48 3.5.3Sensor with K = 151 3.5.4Sensor with K = 054 3 Training manual 4 Inductive proximity switches of ifm 56 4.1Mechanical properties56 4.1.1Structure in general56 4.1.2Chronological development56 4.1.3Modular technology60 4.1.4Application of the efectorm 62 4.1.5Production of the efectorm 63 4.2Designs63 4.3Electrical data65 4.3.1Important parameters65 4.3.2Overview67 4.4Switches with special features68 4.4.1Use in hazardous areas68 4.4.2Switch for quarter-turn actuators69 4.4.3Units with mounting aid70 4.4.4quadronorm units72 4.4.5Non polarised units73 4.4.6Self-monitoring systems73 4.4.7Weld-field immune units74 4.4.8Units with increased operating distance77 4.4.9Units for overflush mounting78 4.4.10Special correction factors, K1, K080 4.5Criteria for practical use82 5 Application examples 85 Annex 90 Technical glossary 91 Type key 96 Production code 98 Index 99 º´«·¼ •»²•±®• ¿²¼ ¼·¿¹²±•¬·½ •§•¬»³• °±•·¬·±² •»²•±®• ¿²¼ ±¾¶»½¬ ®»½±¹²·¬·±² ¾«•ô ·¼»²¬·º·½¿¬·±² ¿²¼ ½±²¬®±´ •§•¬»³• 4 Induticve Sensors 1 Introduction 1.1 Proximity switches in industrial processes What for? Automated production processes require sensors for supplying information. They provide signals about positions, limits, levels or serve as pulse pick-ups. Without reliable sensors even the best controller is not able to control processes. In general, all these sensors consist of two parts: The first registers the change in the physical conditions (basic sensor), the second converts the signals of the basic sensor into electrical output signals (signal processing). In general, a distinction is made between binary sensors which provide a defined high-low signal and analogue sensors which are preferably used for temperature, distance, pressure, force measurement, etc. The sensor supplies an analogue signal which is further analysed for measurement and control. Figure 1: Structure of a sensor SensorThe figure shows the general diagram which basically applies to every sensor. The sensors only differ in some details, e.g. individual components are not used or cannot be used separately. Sometimes the basic sensor is also called just sensor. In this case it must be seen from the context whether the whole unit or the basic sensor is meant. Some units consist of separate components, e.g. NAMUR sensors or often also temperature sensors. Here the transducer is connected to a separate evaluation unit or amplifier. IntelligentIn Figure 1 the characteristic feature of the intelligent sensor is its communication capability. But this term is also used in a different sense. A sensor which only supplies the binary information object detected or object not detected 5 Training manual is in general not called intelligent. But a sensor which is able to supply additional information, e.g. object reliably detected or object unreliably detected is considered to be intelligent. Binary and digital In order to avoid misunderstandings the difference is briefly explained. Binary means "two states" (on/off). An analogue signal which can have any value within certain limits is often digitized today so that it can be processed in electronic controllers. This is done using an A/D converter (analogue to digital). It divides the analogue signal into steps. The number of steps results from the number of the bits used. Whereas one bit can only take two values, 8 bits can take 256 and 10 bits 1024. This is also called resolution. Less than 8 bits are seldom used because the resolution would then be too coarse. More than 12 bits are also seldom used because it does not make sense if the resolution is much higher than the measurement accuracy. Encoders are an exception. They provide digital signals straight away (see training manual encoders). This text mainly deals with binary sensors as replacement for mechanical switches. It provides information about the operating principle, features and criteria for using inductive sensors. Furthermore it presents typical applications and suitable types to make it easier for the user to select the right unit for his application. Many names are used for inductive sensors: Proximity switch, initiator, inductive sensor, non-contact position sensor. In addition, manufacturer-specific names are also used, e.g. efector (registered trademark of ifm electronic gmbh). The term proximity switch, however, is standardised and used in the following text. In industrial applications mainly one system has been tried and tested: Inductive proximity switches. These sensors are suitable for the non- contact detection of a wide range of different conductive materials. ifm has produced non-contact proximity switches for over 30 years. They are used in all industrial applications. What makes these units and in particular the efectors so successful? The inductive sensor withstands interference best (see training manual photoelectric sensors). With the experience of the past decades the units have been improved. For more than 20 years ifm has granted a 5-year warranty for standard units. Due to its high reliability the inductive proximity switch has virtually replaced the mechanical switch. Moreover, new applications come up again and again where a high degree of automation was inconceivable in the past. Next generationWhen the electronic proximity switch was launched it was simply seen as a replacement for the mechanical switch which has now been replaced. This means different types were developed, produced and sold to the user who contacted the manufacturer if the sensor needed additional features in his application. After many years of experience with the units another point of view can be taken. The first question now is: What features does a sensor need for a certain application? Are there any examples? In the food industry for example the following conditions must be taken into account: º´«·¼ •»²•±®• ¿²¼ ¼·¿¹²±•¬·½ •§•¬»³• °±•·¬·±² •»²•±®• ¿²¼ ±¾¶»½¬ ®»½±¹²·¬·±² ¾«•ô ·¼»²¬·º·½¿¬·±² ¿²¼ ½±²¬®±´ •§•¬»³• 6 Induticve Sensors Temperature shocks (cooled fruit juice hot cleaning liquid) New cleaning agents (are to creep into all crannies to remove build- up, residues, i.e.: high demands on ingress resistance) Aggressive media (fruit juice also contains acids!) e.g. in metalworking Coolants (surface wetting increasingly improved, i.e. there are also high demands on ingress resistance, moreover the medium can react with the sensor materials) To fulfil such requirements, the efectorm was developed as a new generation. It is described in section 4.1 how the above-mentioned conditions (temperature, ingress resistance, materials) are met. 1.2 Notation For a better understanding a few notations are explained to make reading the text and finding information easier. KeywordsKeywords which refer to the topic to be dealt with in the following section are given in the left margin. What does FAQ mean? This stands for Frequently Asked Questions. This term is also used for modern electronic media. Almost everybody starting to cope with a new task asks the same questions. Sometimes FAQs instead of keywords precede a section. To differentiate them from simple keywords, they are written in italics. ( 4)A figure in round brackets in the left margin refers to a formula used in the text, e.g. see (4). Of course these formulas do not need to be learnt by heart. They are meant to make understanding of the subject easier because a formula similar to an illustration describes a relation more briefly and clearly than many words. 1.3 On the contents Basic information about inductive proximity switches is found in this manual. Important terms and relations are explained, state-of-the-art technology and technical data of ifm units are presented. This results in the following structure. 1. IntroductionThe introduction is followed by the chapter: 2. BasicsHere the physical basics that are useful for a better understanding of the operating principle and features are briefly presented. A few basic terms are explained. 3. Features of the inductive proximity switches Here the limitation to binary sensors is discussed. Other more complex systems in practical use are presented. Then