Liquid concentration detecting device

1. A liquid concentration detecting device, adapted for detecting a concentration of a liquid, comprising:

a first substrate, having a first surface and a second surface opposite to each other;

a first temperature sensing element, disposed on the first surface and sensing a temperature of the liquid in the external of the liquid concentration detecting device;

a concentration sensor, disposed on the second surface, comprising:

a second substrate, disposed on the second surface, having a third surface and a fourth surface opposite to each other, wherein the third surface faces the second surface;

a porous element, located above the fourth surface of the second substrate, wherein a portion of the liquid flows into the concentration sensor through the porous element;

a heating element, heating the portion of the liquid flowing into the concentration sensor; and

a second temperature sensing element, sensing a temperature variation of the portion of the liquid flowing into the concentration sensor,

wherein the measured temperature and temperature variation are compared to extrapolate the concentration of the liquid under detection.

2. The liquid concentration detecting device according to claim 1 , wherein the heating element is disposed between the second surface of the first substrate and the third surface of the second substrate, the second temperature sensing element is located on the fourth surface of the second substrate, and the porous element is located on the second temperature sensing element.

3. The liquid concentration detecting device according to claim 1 , wherein the second temperature sensing element is disposed between the second surface of the first substrate and the third surface of the second substrate, the heating element is located on the fourth surface of the second substrate, and the porous element is located on the heating element.

4. The liquid concentration detecting device according to claim 1 , wherein both the second temperature sensing element and the heating element are located on the fourth surface of the second substrate, and both the second temperature sensing element and the heating element are disposed between the second substrate and the porous element.

5. The liquid concentration detecting device according to claim 1 , further comprising:

a first sealing layer, disposed between the concentration sensor and the first substrate.

6. The liquid concentration detecting device according to claim 1 , further comprising:

a first sealing layer, disposed between the heating element and the second temperature sensing element.

7. The liquid concentration detecting device according to claim 1 , further comprising:

a second sealing layer, disposed between the second temperature sensing element and the porous element.

8. The liquid concentration detecting device according to claim 1 , further comprising:

a third sealing layer, disposed on a surface of the first temperature sensing element which is away from the first surface of the first substrate.

9. The liquid concentration detecting device according to claim 1 , wherein the porous element is a single-layer structure.

10. The liquid concentration detecting device according to claim 1 , wherein an absorption of the porous element is greater than 15%.

11. The liquid concentration detecting device according to claim 1 , wherein a material of the porous element is ceramic.

12. The liquid concentration detecting device according to claim 1 , wherein at least one of the first substrate and the second substrate is a ceramic substrate.

13. The liquid concentration detecting device according to claim 1 , wherein thermal conductivity coefficients of the first substrate and the second substrate are greater than 20W/M*K.

14. The liquid concentration detecting device according to claim 1 , wherein the first temperature sensing element and the second temperature sensing element are resistance temperature detectors, thermistors or combinations thereof.

15. The liquid concentration detecting device according to claim 1 , further comprising:

a plurality of first electrical contacts, disposed on at least one of the third surface and the fourth surface of the second substrate, and the heating element and the second temperature sensing element are electrically connected with the different first electrical contacts respectively.

16. The liquid concentration detecting device according to claim 1 , further comprising:

a second electrical contact, disposed on at least one of the first surface and the second surface of the first substrate, and the first temperature sensing element is electrically connected with the second electrical contact.

17. The liquid concentration detecting device according to claim 1 , further comprising:

a thermal insulation layer, disposed between the first substrate and the heating element.

18. The liquid concentration detecting device according to claim 1 , wherein the porous element is cover-shaped and covers the second temperature sensing element.

19. The liquid concentration detecting device according to claim 18 , wherein a gap is between the porous element and the second temperature sensing element along a height direction of the liquid concentration detecting device.

20. The liquid concentration detecting device according to claim 19 , wherein the porous element has a pair of openings disposed opposite to each other, and the liquid is adapted to flow in and out through the openings.