Editing Hydrometer (section)

===Thermohydrometer===
A thermohydrometer is a hydrometer that has a [[thermometer]] enclosed in the float section. For measuring the density of petroleum products, such as fuel oils, the specimen is usually heated in a temperature jacket with a thermometer placed behind it since density is dependent on temperature. Light oils are placed in cooling jackets, typically at 15&nbsp;°C.
Very light oils with many volatile components are measured in a variable volume container using a floating [[piston]] sampling device to minimize light end losses.<ref>{{Cite book|title=Instrument and automation engineers' handbook: measurement and safety|publisher=Taylor & Francis Group, CRC Press|year=2017|isbn=978-1-4987-2764-8|editor-last=Béla G. Lipták|location=United States|pages=1314|editor-last2=Kriszta Venczel|edition=Fifth}}</ref>