Adipose tissue#Body fat meter
A body fat scale is a bathroom scale that measures body fat percentage of the human body using four electrodes. The electrodes are mounted on the bottom surface of the scale, that a respective ( bare ) foot on one or two electrodes.
The measurement accuracy is relatively low. The measurement results vary on different scales. Next may influence the results strongly a full bladder or dehydration by physical effort. A reasonably reliable information is obtained only if one always measures at the same time of day under the same conditions. Good comparable conditions are generally achieved every morning after using the toilet or before showering (dry skin ). Ultimately is possible in this way, only the monitoring of personal change.
As a reliable method for the absolute measurement of body fat the Caliper method is commonly used by doctors.
Measuring principle ( simple)
Most of the complex resistance of the body is determined with a four-wire measurement. Two electrodes while a small alternating current (<2 mA) injected and measured at the other two electrodes, the voltage drop. The influence of the contact resistance between the electrode and the skin is minimized by the measurement method. The difference in water content of fat and muscle tissue causes various complex electrical resistances. For resistance values at different AC frequencies, an integrated in the scale computers by an electrical equivalent model of the human body calculate the approximate body fat percentage. By specifying additional information ( weight, gender, age) can be from the amount of body fat and muscle mass are derived.
In simple body fat scales can cause measurement inaccuracies. It changes play in the conductivity of the skin surface by moisture a role. This moisture will affect the resistive component of the measured impedance. On the accuracy of the number of measurements, the frequencies used, the measurement resolution of the phase shift and the swap model used affect.
The general problem of such scales is that the current is passed from one foot to the other and thus only the body fat percentage is hüftabwärts measured. On the fatty tissue above statistically based on other information (age, gender) must be closed.
Measuring principle (extended)
Even for private use body fat scales are now available that have additional electrodes in handles. This will identify more accurate values , as more measured and less extrapolated data are based. All distances between the four measuring points are initially measured individually and then charged. The surface moisture of the skin can distort the readings but also here.