Apparatus for measuring body fat and method thereof

1. A method of measuring body fat of a user, the method comprising:

measuring a first impedance of the user by using a 4-point measuring method, wherein the measuring of the first impedance comprises applying, by a current source, a constant current through two first electrodes among four electrodes while measuring, by a voltage meter, a voltage across two second electrodes among the four electrodes;

measuring a second impedance of the user by using a 2-point measuring method, wherein the measuring of the second impedance comprises respectively connecting the two first electrodes to the two second electrodes via measuring method changing switches, to form two electrodes and measuring the second impedance by using the two formed electrodes;

determining a bio-impedance of the user based on the first impedance and the second impedance, and by closing a first switch and opening a second switch to transmit a value of the first impedance to a look-up table via the first switch while the 4-point, measuring method is performed, and opening the first switch and closing the second switch to transmit a value of the second impedance to the look-up table via the second switch while the 2-point measuring method is performed; and

determining a body fat percentage of the user by using the bio-impedance and body information of the user, wherein the first switch is disposed between the look-up table and an impedance measuring circuit that includes the current source, the voltage meter, and the measuring method changing switches, and

wherein the second switch is disposed between the look-up table and the impedance measuring circuit, and connected in parallel with the first switch.

2. The method of claim 1 , wherein the determining of the bio-impedance is calculated using a central processing unit (CPU) according to the values of the first impedance and the second impedance.

3. The method of claim 1 , wherein the determining the bio-impedance of the user based on the first impedance and the second impedance comprises combining a first formula and a second formula,

wherein the first formula is expressed as:

Z

4

⁢

⁢

P

=

Z

m

⁢

1

1

+

Z

m

+

2

⁢

R

c

Z

i

wherein the second formula is expressed as:

Z

2

⁢

⁢

P

=

1

1

Z

m

+

R

c

+

1

Z

i

wherein Z 4P denotes the first impedance, Z 2P denotes the second impedance, Z m denotes the bio-impedance of the user, R C denotes a contact resistance between the user and the four electrodes, Z i denotes a predetermined impedance of an analog front end of a body impedance measuring circuit that performs the 4-point measuring method and the 2-point measuring method.

4. A non-transitory computer readable medium having embodied thereon a computer program, which when executed by a computer, performs the method of claim 1 .

5. A body fat analyzer comprising:

a plurality of electrodes configured to contact a user, the plurality of electrodes comprising two first electrodes and two second electrodes;

an impedance measurer configured to measure a first impedance by applying a constant current through the two first electrodes while measuring a voltage across the two second electrodes and measure a second impedance by respectively connecting the two first electrodes to the two second electrodes to form two electrodes and measuring the second impedance by using the two formed electrodes;

a bio-impedance determiner configured to determine a bio-impedance based on the first impedance and the second impedance, and by closing a first switch and opening a second switch to transmit a value of the first impedance to a look-up table via the first switch while the first impedance is measured, and opening the first switch and closing the second switch to transmit a value of the second impedance to the look-up table via the second switch while the second impedance is measured; and

a body fat determiner configured to determine a body fat percentage by using the bioimpedance and body information of the user,

wherein the first switch is disposed between the impedance measurer and the look-up table, and

wherein the second switch is disposed between the impedance measurer and the look-up table and connected in parallel with the first switch.

6. The body fat analyzer of claim 5 , wherein the bio-impedance determiner comprises a central processing unit (CPU) configured to determine the bio-impedance according to the values of the first impedance and the second impedance.

7. The body fat analyzer of claim 5 , wherein the two first electrodes are different than the two second electrodes.

8. The body fat analyzer of claim 5 , wherein the body fat analyzer is a wearable device that the user wears on a wrist.

9. The body fat analyzer of claim 8 , wherein two of the plurality of electrodes are arranged on an inner surface of the wearable device, and two of the plurality of electrodes are arranged on an outer surface of the wearable device.

10. A body fat analyzer comprising:

a plurality of electrodes that come in contact with a user when the user wears the body fat analyzer, the plurality of electrodes comprising four first electrodes and two second electrodes;

an impedance measurer configured to measure a first impedance by applying a constant current through two electrodes among the four first electrodes while measuring a voltage across the other two electrodes among the four first electrodes and measure a second impedance by using the two second electrodes;

a bio-impedance determiner configured to determine a bio-impedance based on the first impedance and the second impedance, and by closing a first switch and opening a second switch to transmit a value of the first impedance to a look-up table via the first switch while the first impedance is measured, and opening the switch and closing the second switch to transmit a value of the second impedance to the look-op table via the second switch while the second impedance is measured; and

a body fat determiner configured to determine a body fat percentage by using the bioimpedance and body information,

wherein the first switch is disposed between the impedance measurer and the look-up table, and

wherein the second switch is disposed between the impedance measurer and the look-up table and connected in parallel with the first switch.

11. A device for measuring body fat, the device comprising:

an impedance measurer configured to measure a first body impedance by applying a constant current through two electrodes among a plurality of first electrodes while measuring a voltage across another two electrodes among the plurality of first electrodes and measure a second body impedance using a plurality of second electrodes;

a bio-impedance determiner configured to determine a bio-impedance of a user based on the first body impedance and the second body impedance, and by closing a first switch and opening a second switch to transmit a value of the first impedance to a look-up table via the first switch while the first impedance is measured, and opening the first switch and closing the second switch to transmit a value of the second impedance to the look-up table via the second switch while the second impedance is measured; and

a body fat determiner configured to determine a body fat percentage of the user based on the determined bio-impedance and body information of the user;

wherein the first switch is disposed between the impedance measurer and the look-up table, and

wherein the second switch is disposed between the impedance measurer and the look-up table and connected in parallel with the first switch.

12. The device of claim 11 , wherein the plurality of first electrodes are a first size and the plurality of second electrodes are a second size different from the first size.

13. A method of measuring body fat of a user comprising:

measuring a first impedance of the user by applying a constant current from a current source to two electrodes among a first number of first electrodes while measuring, by a voltage meter, a voltage across another two electrodes among the first number of first electrodes;

measuring a second impedance of the user using a second number of electrodes;

determining a bio-impedance of the user based on the first and second impedances, and by closing a first switch and opening a second switch to transmit a value of the first impedance to a look-up table via the first switch while the first impedance is measured, and opening the first switch and closing the second switch to transmit a value of the second impedance to the look-up table via the second switch while the second impedance is measured; and

determining the body fat of the user using the bio-impedance and body information of the user,

wherein the first switch is disposed between the look-up table and an impedance measuring circuit that includes the current source and the voltage meter, and

wherein the second switch is disposed between the look-up table and the impedance measuring circuit, and connected in parallel with the first switch.

14. The method of claim 13 , wherein the first number of electrodes is four and the second number of electrodes is two.

15. The method of claim 14 , wherein the four electrodes used in measuring the first impedance are different from the two electrodes used in measuring the second impedance.

16. The method of claim 14 , wherein the two electrodes used in measuring the second impedance are also used in measuring the first impedance.

17. The method of claim 14 , wherein the four electrodes used in measuring the first impedance are identical in size.

18. The method of claim 14 , wherein each of the two electrodes used in measuring the second impedance is greater in size than each of the four electrodes used in measuring the first impedance.

19. The method of claim 13 , wherein a same level of current is applied to the user while measuring the first and second impedances.