Other sensors can use LEDs tuned to {HEAD ~ frequencies} which are absorbed in different amounts by {TAIL ~ the gases} typically used for welding 
are absorbed by
Other sensors can use LEDs tuned to { HEAD ~ frequencies } which are absorbed in different amounts by { TAIL ~ the gases } typically used for welding
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH REL REL OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH