A system 1, wherein the system comprises {HEAD ~ a phase locked loop} for measuring {TAIL ~ the amplitude} of a photoacoustic signal 
A system 1 , wherein the system comprises { HEAD ~ a phase locked loop } for measuring { TAIL ~ the amplitude } of a photoacoustic signal
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH