A wireless device for measuring hand-applied forces

We report on a wireless, electromyography (EMG)-based, force-measuring system developed to quantify hand-applied loads without interfering with grasping function. A portable surface EMG device detects and converts to voltage output biopotentials generated by muscle contractions in the forearm and upper arm during hand-gripping and traction activities. After amplifying and bandpass filtering, our radio frequency (RF)-based design operating at ∼916 MHz wirelessly transmits those voltages to a data acquisition (DAQ) system up to 20 meters away. A separate calibration system is used to relate an individual user´s EMG signal to known pull and clenching forces during specific applications. Real-time EMG data is processed and displayed in software developed with LabView™ (National Instruments, Austin, TX). Data is then converted to force data using individual calibration curves. With EMG electrodes placed over any major forearm muscle, calibration curves for seven subjects demonstrated linearity (R² > 0.9) and repeatability (<10% of average slope) to 110 newtons (N). Preliminary results in clinical application on newborn delivery suggest that this approach may be effective in providing an unobtrusive and accurate method of measuring hand-applied forces in applications such as rehabilitation and training.