Pipe to soil {HEAD ~ potential measurements} are carried out between the reference electrode and a connection to the pipe using a wireless transmission system or using an electrical power grid neutral or ground wire as the conductor between the pipe and {TAIL ~ the reference electrode} 
Pipe to soil { HEAD ~ potential measurements } are carried out between the reference electrode and a connection to the pipe using a wireless transmission system or using an electrical power grid neutral or ground wire as the conductor between the pipe and { TAIL ~ the reference electrode }
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL