A method for calibrating a photoacoustic
system (100) for detecting the concentration of fluids, said method comprising a step of prearranging a photoacoustic
system for fluids (100) comprising a support (105) arranged to receive a fluid to be examined, a primary optical source (110), a secondary optical source (120), an electronic
system comprising a
control unit arranged to drive the primary optical source (110) and the secondary optical source (120) by means of two respective periodic signals s1(t) and s2(t), an acoustic
transducer (130) arranged to acquire an
acoustic response signal p M . The method also comprises the steps of selecting a fluid to be examined having a plurality of absorption peaks p i in the
electromagnetic spectrum, associated with corresponding wavelengths λi, with i = 1,2,..., n; in the plurality of absorption peaks p i , selecting an absorption peak p* associated with a corresponding
wavelength λ*; defining a first
wavelength interval between two end wavelengths λ*1A and λ*1B, where λ*1A <λ*<λ*1B; defining a second
wavelength interval between two end wavelengths λ*2A and λ*2B, where λ*2A <λ*<λ*2B, and where λ*2A < λ*1A and λ*2B > λ*1B; by the primary optical source (110), transmitting toward the support (105), without fluid, an
electromagnetic radiation having a wavelength λ1, such that λ*1A < λ1 < λ*1B; by the secondary optical source (120), transmitting toward the support (105), without fluid, an
electromagnetic radiation having a wavelength λ2, such that λ2 < λ*2A or λ2 > λ*2B; by the acoustic
transducer (130), acquiring an
acoustic response signal p M = p w1 +p w2 ; iterating the steps of variation of the values of I2 and φ2, emission of the electromagnetic radiations having wavelengths λ1 and λ2, acquisition of the
acoustic response signal p M = p w1 +p w2 ; suspending the iteration when the condition p M = p* M is reached, where p* M is a predetermined value.