The output signal of the transducer is amplified and then processed by {HEAD ~ a data processing unit} to calculate {TAIL ~ the propane gas concentration} 
to calculate
The output signal of the transducer is amplified and then processed by { HEAD ~ a data processing unit } to calculate { TAIL ~ the propane gas concentration }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL