All types of resistors have their own resistor symbols which are used when a circuit diagram is drawn. This page will explain the different standards which are used for resistor symbols and display the most common symbols. Standards for resistor symbols Several standards exist, which describe how the different components should be displayed. In the past a lot of countries or even industries used their own standards, which can be confusing. Nowadays the IEC 60617 standard is international standard for these electronic symbols. However the local standards are still used from time to time. In general, the ANSI standard is still common in the United States. Some examples of standards which describe resistor symbols: IEC 60617 (International) ANSI Y32 / IEEE 315 (US) – old DIN 40900 (Germany) – old AS 1102 (Australia) – old Sometimes the symbol for a particular device is different when it is used in another field of application. Other symbols are used in electronics then for example in architecture and buildings. On top of this, many local deviations from the international standards exist. The following table shows the most common resistor symbols for electronics design. Schematic symbols Type Abbreviation IEC (International) ANSI (US) Fixed resistor R Heating resistor Variable resistors VR Potentiometer Trimming potentiometer Rheostat Preset resistor Dependent resistors Photo resistor orLight dependent resistor LDR Varistor or Voltage dependent resistor VDRRVMOV NTC thermistor NTCRT PTC thermistor PTCRT Magneto resistor orMagnetic dependent resistor MDR Read more in the Resistor Guide E-Book.
What is a fixed resistor? Fixed value resistors have a defined ohmic resistance and are not adjustable. Fixed resistors are the most commonly used resistors and in general one of the most used electronic components. Fixed resistors are available in axial leaded and surface mount packages as well as more customized packages depending on their application. While axial leaded resistors used to be the most used resistors, nowadays the advantages of surface mount devices make the SMD resistors the most popular. Fixed resistor definition A resistor having a fixed, defined electrical resistance which is not adjustable. In an ideal world a perfect resistor would have a constant ohmic resistance under all circumstances. This resistance would be independent of for example frequency, voltage or temperature. In practice no resistor is perfect and all resistors have a certain stray capacitance and inductance, resulting in an impedance value different from the nominal resistance value. The resistor materials have a certain temperature coefficient, resulting in a temperature dependency of the resistor value. The different resistor types and materials determine the dependency of the resistance value on these external factors. Depending on e.g. the required accuracy, power dissipation and noise requirements, the type and material of resistor are selected. Some common types of fixed resistors are displayed below. For a complete overview of the basic properties and applications of standard resistors, take a look at the article ‘What is a resistor‘. Identifying fixed value resistors In the following table an overview of general purpose resistors is given. The types listed here are among the most used resistors in general. The carbon film is the most common axial leaded resistor which is used for applications where a very good tolerance and temperature coefficient are not necessary. The metal film is the general axial leaded resistor of [… read more]