Method for determining a property of a sample fluid or a resonant frequency of a resonator cell

A method having the following steps:

• a) according to a first alternative, providing an acoustic resonator, the acoustic resonator comprising an absorption element having a surface portion,
• providing a sample fluid or a fluid mixture comprising the sample fluid such that the acoustic resonator is filled with the sample fluid or the fluid mixture comprising the sample fluid,
• wherein the surface portion of the absorption element is in contact with the sample fluid or the fluid mixture comprising the sample fluid,
• or
• according to a second alternative, providing an acoustic resonator,
• providing a fluid mixture comprising a sample fluid such that the acoustic resonator is filled with the fluid mixture,
• wherein the fluid mixture comprises, in addition to the sample fluid, at least one absorption fluid or one or more absorption particles,
• b) according to the first alternative, irradiating the surface portion of the absorption element with a first electromagnetic radiation such that the absorption element at least partially absorbs the first electromagnetic radiation in the region of the surface portion,
• or
• according to the second alternative, irradiating the fluid mixture with a first electromagnetic radiation such that the absorption fluid or the absorption particles at least partially absorb the first electromagnetic radiation,
• such that, in both alternatives, by way of the absorption, pressure energy is produced in the sample fluid or the fluid mixture comprising the sample fluid, wherein the first electromagnetic radiation is amplitude modulated or frequency modulated at a modulation frequency,
• c) measuring an acoustic response signal of the acoustic resonator generated by the absorption of the first electromagnetic radiation taking place in step b),
• d) determining at least one amplitude or phase of the acoustic response signal having the modulation frequency of the first electromagnetic radiation,
• wherein the first electromagnetic radiation comprises a frequency of the alternating electromagnetic field, wherein the frequency of the alternating electromagnetic field is not equal to an absorption frequency of the sample fluid.

A method having the following steps:

• a) according to a first alternative, providing an acoustic resonator, the acoustic resonator comprising an absorption element having a surface portion,
• providing a sample fluid or a fluid mixture comprising the sample fluid such that the acoustic resonator is filled with the sample fluid or the fluid mixture comprising the sample fluid,
• wherein the surface portion of the absorption element is in contact with the sample fluid or the fluid mixture comprising the sample fluid,
• or
• according to a second alternative, providing an acoustic resonator,
• providing a fluid mixture comprising a sample fluid such that the acoustic resonator is filled with the fluid mixture,
• wherein the fluid mixture comprises, in addition to the sample fluid, at least one absorption fluid or one or more absorption particles,
• b) according to the first alternative, irradiating the surface portion of the absorption element with a first electromagnetic radiation such that the absorption element at least partially absorbs the first electromagnetic radiation in the region of the surface portion,
• or
• according to the second alternative, irradiating the fluid mixture with a first electromagnetic radiation such that the absorption fluid or the absorption particles at least partially absorb the first electromagnetic radiation,
• such that, in both alternatives, by way of the absorption, pressure energy is produced in the sample fluid or the fluid mixture comprising the sample fluid, wherein the first electromagnetic radiation is amplitude modulated or frequency modulated at a modulation frequency,
• c) measuring an acoustic response signal of the acoustic resonator generated by the absorption of the first electromagnetic radiation taking place in step b),
• d) determining at least one amplitude or phase of the acoustic response signal having the modulation frequency of the first electromagnetic radiation,
• wherein in a further step, a property of the acoustic resonator is determined.

A device having

• at least one radiation source for generating a first electromagnetic radiation,
• an acoustic resonator comprising an absorption element having a surface portion, the surface portion of the absorption element being arranged such that the surface portion is in contact with a sample fluid or a fluid mixture comprising the sample fluid when the acoustic resonator is filled with the sample fluid or the fluid mixture comprising the sample fluid,
• wherein the absorption element is configured to at least partially absorb the first electromagnetic radiation in the region of the surface portion such that pressure energy is generated in the sample fluid or the fluid mixture comprising the sample fluid when the acoustic resonator is filled with the sample fluid or the fluid mixture comprising the sample fluid,
• a sonic sensor for measuring an acoustic response signal of the acoustic resonator,
• wherein the at least one radiation source and the acoustic resonator are configured and arranged such that the first electromagnetic radiation is incident upon the surface portion of the absorption element,
• wherein a radiation source is provided for generating a second electromagnetic radiation,
• wherein the acoustic resonator comprises a first opening or a first window at least partially transparent for the second electromagnetic radiation, wherein the acoustic resonator and the radiation source of the second electromagnetic radiation are configured and arranged such that the second electromagnetic radiation passes through the first opening or the first window into the acoustic resonator, and
• wherein the acoustic resonator comprises a second opening or a second window, which is at least partially transparent for the second electromagnetic radiation, wherein the acoustic resonator and the radiation source of the second electromagnetic radiation are configured and arranged, such that the second electromagnetic radiation passes through the second opening or the second window out of the acoustic resonator.