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4. DKE

DKE German Commission for Electrical, Electronic & Information Technologies of DIN and VDE

Overview

The standard DIN EN 60440 describes a method of measurement of non-linearity in resistors. This is a method to evaluate the integrity of a resistive element. It may be applied as an effective inline screening method suitable to detect and eliminate potential infant mortality failures in passive components. The method is fairly rapid, convenient, and the associated equipment is relatively inexpensive. The responsible committee is GK 613 "Widerstände" ("Resistors") of the DKE (German Commission for Electrical, Electronic and Information Technologies) at DIN and VDE. Non-linearity is the deviation of a component's impedance from Ohm's law, resulting in voltage of harmonic frequencies when subjected to sinusoidal current. Typical effects causing non-linearity on resistors are, for instance inhomogeneous spots within a resistive film, traces of film left in the spiraling grooves, or contact instability between a connecting lead or termination and the resistive element. This standard specifies a method of measurement and associated test conditions to assess the magnitude of non-linear distortion generated in a resistor. This method is applied if specified by a relevant component specification, or if agreed between a customer and a manufacturer. The component to be tested is charged with a purely sinusoidal current. When the component's impedance is not precisely linear, the voltage is distorted across the component and contains harmonic frequencies. One or more of these harmonic frequencies can be measured and the magnitude of these distortions represents a measure for non-linearity of the component. It is recommended to measure the third harmonic as this is the prevailing harmonic frequency. For the measurement the third order harmonic voltage occurring above the component shall be separated from the fundamental voltage and all other harmonic voltages. This is achieved with the aid of a filter circuit which allows the harmonic voltage to pass through while exhibiting very high impedance during third order harmonic frequencies. The fundamental frequency generator is also required to exhibit very high impedance during third order harmonic frequency in order not to take effect as a charge during the generated distortion. When the measurement is performed the specimen shall be placed in the test apparatus and shall be properly connected to the test terminals. The impedance of the measurement system R3 shall be selected in such a manner that the best possible impedance matching is achieved. The fundamental voltage shall be applied, for instance, by closing the switch S and shall be set to the specified value. The third order harmonic voltage U3 shall be read off.

Document: references other documents

Responsible national committee

DKE/GK 613 - Widerstände