Copy variation

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The term " specimen variance " used in production technology means : A characteristic property of a component or technical device is not identical in series production, but there are deviations from a reference value and from each other for each individual part or batch . The characteristic values ​​for different copies of the same type are different.

Examples

The marking of this resistor contains a statement in the color of the right ring about the specimen variance

In the simple case of the resistor shown opposite, its nominal value is indicated by three colored rings and its limit deviation by a fourth ring . The gold ring on the far right indicates that the resistance of the specimen can vary by up to 5% from its nominal value.

Semiconductor components cannot even be produced with the desired uniformity with regard to several characteristic properties. Furthermore, the sample spread can be considerably wider. For example, for a transistor type, in addition to the typical value, a scatter range is specified under specified conditions:

  • the direct current amplification factor with typically 290, minimum 200, maximum 450
  • the base-emitter voltage with typically 660 mV, minimum 580 mV, maximum 700 mV.

Or for an operational amplifier type, for example, in addition to the typical value, the value that occurs in the worst case under specified conditions is specified:

  • the input quiescent current with typically 80 nA, maximum 500 nA
  • the DC voltage gain factor with typically 200,000, minimum 50,000
  • the input offset voltage with typically 1 mV, maximum 5 mV.

In the case of such specimen variations, the design of the electrical circuit ( operating point stabilization , negative feedback ) must ensure that the property of the circuit produced with such a component is independent of these properties of the component within the scope of the variation range.

In the case of sensors , sample deviations of zero point and slope (as well as non-linearities and defined influencing effects) are consciously accepted. A microcomputer takes over the correction of the individual characteristic. The required parameters are determined as part of a calibration .

Demarcation

The specimen variance is to be distinguished from the tolerance , which states which deviation from the normal state does not yet require any countermeasures or which does not yet endanger the function of a system.

Individual evidence

  1. ↑ Detlef Gronwald, Martin Wolf: Teaching-oriented introduction to electrical engineering. Vieweg, 1982, p. 258
  2. ↑ Data sheet BC564B. P. 2 , accessed November 25, 2016 .
  3. ↑ Data sheet 741, p. 5 , accessed on November 25, 2016 .
  4. ↑ Erwin Böhmer, Dietmar Ehrhardt, Wolfgang Oberschelp: Elements of applied electronics: Compendium for training and occupation. Vieweg + Teubner, 16th ed., 2010, p. 138 f
  5. ^ Ekbert Hering, Klaus Bressler, Jürgen Gutekunst: Electronics for engineers and scientists. Springer – Vieweg, 6th edition, 2014, p. 215
  6. ↑ Hans-Rolf Tränkler: Pocket book of measuring technology: with a focus on sensor technology. , Oldenbourg, 2nd ed., 1990, p. 249