In order to eliminate false alarms,issued by gas sensors in coal mining,caused by Electromagnetic Interference(EMI),both computer simulation and field measurements were introduced to analyze the underground EMI distri...In order to eliminate false alarms,issued by gas sensors in coal mining,caused by Electromagnetic Interference(EMI),both computer simulation and field measurements were introduced to analyze the underground EMI distribution.A simplified model of a sensor with metal enclosure was established and the effects of shielding properties about the enclosure aperture were studied.Because the haulage motor is the moving EMI source,varying with time,the onsite flameproof measuring instruments cannot accomplish synchronous measurements of electromagnetic field vectors.To simplify the field measurements,two sensors,one with a lead and the other without a lead,were chosen to conduct the contrasting measurements.The EMI current caused by the perforation lead was comparatively strong and therefore nickel zinc ferrite beads were used to cut off the EMI propagation paths.The peak value of the interference current was reduced by 20%-70% with the beads.After switching on the sensor power,the sen-sors still occasionally gave false alarms when the switch of nearby large-scale electric equipment was operated.A complex EMI filter was used and the EMI attenuated markedly.The running results demonstrated that false alarms had been eliminated.We con-clude that the improved shielding and filtering are highly significant in enhancing the immunity of the gas sensor.展开更多
In optical performance monitoring system,the analog to digital converter is needed to detect the peak of nanosecond pulse and get the signal envelope.A scheme based on a designed anti-aliasing filter and analog to dig...In optical performance monitoring system,the analog to digital converter is needed to detect the peak of nanosecond pulse and get the signal envelope.A scheme based on a designed anti-aliasing filter and analog to digital converter is proposed to broaden the nanosecond pulse and make it easier for the analog to digital converter to catch the peak of the nanosecond pulse.The experimental results demonstrate that,with the proposed scheme,the optical performance system needs less time to get the recovered eye-diagram of high speed optical data signal,and is robust to phase mismatch in the analog to digital converter circuit.展开更多
基金Project 50674093 supported by the National Natural Science Foundation of China
文摘In order to eliminate false alarms,issued by gas sensors in coal mining,caused by Electromagnetic Interference(EMI),both computer simulation and field measurements were introduced to analyze the underground EMI distribution.A simplified model of a sensor with metal enclosure was established and the effects of shielding properties about the enclosure aperture were studied.Because the haulage motor is the moving EMI source,varying with time,the onsite flameproof measuring instruments cannot accomplish synchronous measurements of electromagnetic field vectors.To simplify the field measurements,two sensors,one with a lead and the other without a lead,were chosen to conduct the contrasting measurements.The EMI current caused by the perforation lead was comparatively strong and therefore nickel zinc ferrite beads were used to cut off the EMI propagation paths.The peak value of the interference current was reduced by 20%-70% with the beads.After switching on the sensor power,the sen-sors still occasionally gave false alarms when the switch of nearby large-scale electric equipment was operated.A complex EMI filter was used and the EMI attenuated markedly.The running results demonstrated that false alarms had been eliminated.We con-clude that the improved shielding and filtering are highly significant in enhancing the immunity of the gas sensor.
基金supported by National 863 Program of China(2013AA013401),P.R.ChinaNational Natural Science Foundation of China under Grant No.61177067,No.61027007,and No.61331010
文摘In optical performance monitoring system,the analog to digital converter is needed to detect the peak of nanosecond pulse and get the signal envelope.A scheme based on a designed anti-aliasing filter and analog to digital converter is proposed to broaden the nanosecond pulse and make it easier for the analog to digital converter to catch the peak of the nanosecond pulse.The experimental results demonstrate that,with the proposed scheme,the optical performance system needs less time to get the recovered eye-diagram of high speed optical data signal,and is robust to phase mismatch in the analog to digital converter circuit.
