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Siemens AG
Entry type: FAQ Entry ID: 109761014, Entry date: 11/14/2018
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Use of gold contacts for SIRIUS ACT

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This entry provides information on the use of gold contacts.

QUESTION:

When are gold contacts recommended?

 

 

ANSWER:

A gold contact is recommended in the following applications:

 

  • Switching low powers (< 1 volt and a few milliamps)
    Note: Gold is intrinsically resistant to oxidation and sulfidation, so it doesn't form an oxide or sulfide layer that increases contact resistance. When low powers are switched, no arcing – which cleans these layers (oxide or sulfide) electrically – occurs, which is why this has to be prevented by the gold contact. 
  •  Low-demand applications

Note: Characteristic of low-demand applications are switching frequencies of a few operations per year or just one switching operation in x years. Due to the lack of mechanical movement of the switching contact, it can become so highly resistant from the oxide or sulfide layer that the evaluation electronics are no longer able to reliably detect the signals to be switched.

 

  • Chemically aggressive environments
    Note: Silver is liable to disintegrate in chemically aggressive environments, as a result of which contact is no longer ensured.
  •  Poultry and pig fattening operations

Note: Ammoniac exposure in poultry and pig fattening operations can corrode the silver contacts and damage them. The gold coating is not affected by the ammonia.

 

 

A gold contact is not recommended in the following applications:


  • Inductive circuits
    Note: In inductive circuits, the gold plating is corroded by the inrush current.
  • For frequent switching cycles

Note: Gold contacts are worn down quicker than silver contacts as a result of frequent switching cycles.


  • For higher powers
    Note: The arcing that occurs would burn away the gold layer more rapidly and thus shorten service life.



Summary:
To sum up, we can say that gold contacts should be used in chemically aggressive environments and for switching low powers with high contact reliability. For the remaining applications, e.g. signaling for the PLC and high switching frequencies with high power, silver contacts are recommended.



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