Such sensors may, alternatively, detect {HEAD ~ the pressure} of {TAIL ~ the fluid} on either side of the piston head of such a system, for example 
of
Such sensors may , alternatively , detect { HEAD ~ the pressure } of { TAIL ~ the fluid } on either side of the piston head of such a system , for example
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH