NIST DEVELOPS METAL DETECTOR EMULATOR TO STUDY ADVERSE EFFECTS ON MEDICAL DEVICES.

With the widespread use of metal detectors for security purposes in courthouses, penal institutions, and airports, a risk may exist for users of personal medical electronic devices (PMEDs) because of electromagnetic interference (EMI) from the magnetic fields generated by the metal detectors. An analysis of more than 80 medical device reports between 1987 and 2000 by the Food and Drug Administration's (FDA's) Center for Devices and Radiological Health reveals likely adverse interactions between the fields produced by metal detectors and PMEDs, such as cardiac pacemakers, implantable cardiac defibrillators, and drug infusion pumps.

An emulator that simulates the linearly-polarized magnetic fields of walk-through metal detectors was developed by NIST researchers for the FDA to conduct EMI tests of PMEDs. The emulator consists of a current source and specially designed coil that can simulate magnetic fields with adequate uniformity and with the rapid time varying characteristics found in some walkthrough metal detectors, as well as numerous handheld metal detectors. The electronic components are "off-the-shelf" devices and the specially designed coil system is readily fabricated. A coil fabricated by NIST was recently delivered to the FDA. Because the maximum voltage induced in PMEDs depends upon the time sate of change of the magnetic field, and because higher induced voltages are more likely to have adverse effects on PMEDs, it is important to accurately simulate the magnetic field amplitude and rapid temporal transitions. The emulator was designed to be flexible enough to simulate magnetic field waveforms of metal detectors now being e xamined by the FDA.

A manuscript describing the emulator system was recently submitted to the IEEE Transactions on Electromagnetic Compatibility for consideration as a publication. Because the emulator can be readily fabricated, manufacturers of PMEDs have the option of building their own emulators for conducting EMI tests of their products.