Zeng-S; Powers-JR; Jackson-LJ; Conover-DL
IEEE International Symposium on Circuits and Systems (ISCAS) May 23-26, 2005, International Conference Center, Kobe, Japan. New York: Institute of Electrical and Electronics Engineers, 2005 May; :576-579
An electrical injury protection system is being developed to protect electrical workers from electrical injury and electrocution by human proximity and electrical contact sensing. Proximity is monitored by the insertion loss of radio-frequency (RF) transmission between the power circuit and the human body. The system continuously transmits low power amplitude-shift-keying (ASK) RF waves from the power circuit to the surrounding area. An RF receiver attached to the human body measures the magnitude of incoming ASK RF waves which is inversely related to the proximity of the human body to the power circuit. A novel digital ASK demodulation method is used to efficiently conduct digital measurements of the incoming ASK RF wave magnitude. In this method, the RF receiver converts the incoming ASK signals to saw-tooth-like enveloped ASK RF signals. A digital ASK demodulator demodulates the converted RF signal and digitizes the saw-tooth-like envelopes into square waves with their pulse widths directly related to the magnitude of the incoming ASK RF signals. The wider the pulse width, the stronger the incoming RF wave, and vice versa. Human proximity and electrical contact are digitally detected by counting the width of the demodulated pulses. The current consumption of the prototype receiver is only 9 microamperes which is 1600 times less than that for a conventional ASK magnitude detector.
Electricity; Electrical-workers; Electrocutions; Workers; Electrical-safety; Safety-measures; Monitoring-systems