Development of a new electrical injury protection system-selection of RF transmitter mounting location on the human body.
Zeng S; Powers JR; Jackson LL; Conover DL
NOIRS 2003-Abstracts of the National Occupational Injury Research Symposium 2003, October 28-30, Pittsburgh, Pennsylvania. Pittsburgh, PA: National Institute for Occupational Safety and Health, 2003 Oct; :66
To protect electrical workers near an energized electrical circuit, a new electrical injury protection system is being developed that measures how close a worker is to a live circuit by using a worker-worn low-power radio-frequency (RF) transmitter and a receiver that is plugged into the live electrical circuit. The transmitter emits RF electromagnetic waves through a worker's body to the energized electrical circuit allowing the receiver to judge the worker's proximity or electrical contact by analyzing the RF signal strength. The uniformity of the RF emission strength through the body, which is mainly determined by body-mounting location of the RF transmitter, affects the accuracy of the RF-receiver proximity/electrical contact measurement. After the approval by the CDC/NIOSH Human Subject Review Board, nine human subjects were tested to measure the strength of RF emissions through different parts of their bodies to an electrical circuit. Two practical RF-transmitter-mounting locations, wrist and upper-arm, were tested by attaching an RF signal source (100-150 kHz). The RF signal path is: RF signal source - body transmitter-mounting location - body extremity/ forehead - air (omitted in electrical contact simulation) - electrical circuit - RF spectrum analyzer. Non-uniform RF emission levels were observed through hands and forehead to an electrical circuit. The greatest RF signal strength difference of 9.47 dB (mean) was observed between the left-hand emission and right-hand emission when the RF signals were transmitted from the subject's right wrist. As the RF transmission location was moved from right-wrist to right-upper-arm, the above RF emission strength difference was reduced to 4.20 dB (mean). This RF-emission-uniformity difference may be attributed to the different electrical-path lengths between the signal transmitter location and RF-emitting parts of the body. Thus, continued development of the protection system will use the upper-arm as the RF-transmitter mounting location to most accurately measure human-to-electrical-circuit proximity and electrical contact.
Personal-protective-equipment; Personal-protection; Electrical-workers; Electrical-industry; Injuries; Injury-prevention; Safety-equipment; Safety-measures; Electrical-safety
Abstract; Conference/Symposia Proceedings
NOIRS 2003-Abstracts of the National Occupational Injury Research Symposium 2003, October 28-30, Pittsburgh, Pennsylvania