<a href="https://en.wikipedia.org/wiki/Lock-in_amplifier" class="extiw" title="w:Lock-in amplifier">Lock-in amplifier</a> in experimental setup
<a href="//commons.wikimedia.org/wiki/User:Biezl" title="User:Biezl">Biezl</a>
2010-08-10
<span class="int-own-work" lang="en">Own work</span>