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Hydrometers and Thermohydrometers

Hydrometers and Thermohydrometers

2H - 3H - 5H - 8H

Koehler Instrument Company



Hydrometer method is widely used for measuring °API, density and relative density of Crude Oil, Petroleum Products and LPG. Hydrometer or Thermohydrometer is allowed to float on sample and reading is taken directly on scale; hydrometers require an additional thermometer to read sample temperature while thermohydrometers have a built-in thermometer. In case sample temperature is different from reference temperature, reading needs to be corrected.

Hydrometers and thermohydrometers can be requested with or without calibration as per ASTM E100, call us for more information.

We have available a wide variety of suitable accesories for these tests:

  • Cylinders for samples
  • ASTM thermometers
  • Conditioning baths with heating or for work at under ambient temperatures.
  •  Racks
  • Pressurized cylinders for LPG


References and Features


Hydrometers °API

Standard temperature 60°F, subdivisions 0.1° API, length 330mm. References and ranges:


API Gravity Thermohydrometers -Thermometer in Body

Standard temperature 60°F, subdivisions 0.1° API, length 380mm, thermometer scale °F 0-150 (designation L), 30 to 180 (designation M), 60 to 220 (designation H). References and Ranges:



API Gravity Thermohydrometers -Thermometer in Stem
Standard temperature 60°F, subdivisions 0.1° API, length 380mm, temperature scale °F 30-220. References and Ranges:


Specific Gravity Hydrometers
Standard temperature 60/60°F, subdivisions 0.0005, length 330mm, References and Ranges:


Standard temperature 60/60°F, subdivisions 0.001 length 260mm, References and Ranges:


ASTM Metric Thermohydrometers
Standard temperature 15°C, subdivisions 0.5kg/m3, length 380mm, thermometer scale °C: –20 to +65 (designation L), 0 to 85 (designation M), 20 to 105 (designation H). References and Ranges:




      For more information regarding features, part numbers, quotations and related matters, please send us an e-mail to:

      For more information regarding use of this instrument, applications, instruction manuals and maintenance requests, please send us an e-mail to:





DIN-51757, ISO-3675, IP-160.