Body Composition Testing for All

Patent Number: US 6,631,292 B1

Filing Date: March 23, 2001

Issue Date: October 7, 2003

Inventor(s):  Rudolph J. Liedtke (Grosse Pointe Park, MI)

Assignee: RJL Systems, Inc. (Mt. Clemens, MI)

U.S. Classification: 600/547

Claims: 20


Figure 1. A functional block diagram of a single aspect of a device based on the invention


A bioelectrical impedance analyzer is an apparatus used to determine bioelectrical impedance measurements. This particular analyzer is used to measure a particular area of impedance in a subject. This works by having a constant source of current where the currents input is controlled by a feedback loop. This feedback loop uses an error signal that represents the difference between the actual impedance of the area measured, the target current. The analyzer also contains an impedance measuring circuit that detects and output voltage from the area of the subject. This circuit splits the measured output voltage into a reactance output signal and a resistance output signal. The image above shows a block diagram of the electrical components within this analyzer.

Bioelectrical impedance analyzers can be used to find measurements within the human body. These measurements    can then be used to determine many different things about the body being tested. Using these measurements, blood flow, cardiac output, lean body mass, and body fat can be found for the tested individual. This invention of the bioelectrical impedance analyzer differs from those before it because it separates the electrical components of the analyzer from the individual using it. This is different from previous designs that directly attached electrodes to the individual. Another difference in this invention its temperature insensitivity. This allows the analyzer to be easily portable compared to its related technologies.

This analyzer invention had 20 claims outlining the main components of this device. These claims all referred to the electrical components of the analyzer. The main claims of this invention are that the constant current sources input current is controlled by an internal feedback loop that uses error signals to calculate an output. Another main claim is that the impedance measuring circuit is made to give out both a reactance and a resistance output signal.

This particular bioelectrical impedance analyzer invention would be ideal for any individual who is concerned about their body composition. It is easily portable and safe to use. For example, an individual who is looking to cut body fat, but doesn’t want to pay for the expensive body fat testing, would benefit from this analyzer. This analyzer would also be good for people who are body builders that travel often. This way they would have a way to test their body composition so that they could stay on track with their goals. Having had personal experience using a portable bioelectrical impedance analyzer, I think this would be ideal for someone wanting a close estimate on different body composition measurements. Even though the measurements aren’t as accurate as some other more expensive and invasive techniques, these portable analyzers work great and are more easily accessible. It is interesting to think about how this analyzer will advance and become more accurate in the future.


Liedtke, Rudolph J. (2003). United States Patent No. US6,631,292B1. Retrieved


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