\begin{tikzpicture}
  \node at (0,0) {\includegraphics[height=4.25cm]{sensorhygro}};
  \draw[-latex] (1.75,-0.1) -- (2.,-.75);
  \node at (2.,-.75) [below]{sensor};
  
  \draw[-latex] (-1.5,-0.1) -- (-1.75,-.5);
  \node at (-1.75,-.6) [below]{measurement};
  
  \node at (1,-2.2) {transponder};
\end{tikzpicture}