Sensor apparatus (1) for determining at least one biochemical function of a fluid (F) with at least one magnetoelastic capillary tube (2) through which the fluid (F) is conveyed, wherein a resonant frequency (fR) of the magnetoelastic capillary tube (2), which depends on a surface loading of the inner wall of the magnetoelastic capillary tube (2) by the fluid (F) conveyed through the tube is able to be read out in a non-contact manner for determining the biochemical function of the fluid (F).
