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Digital hydrometer

Digital hydrometers are used for measuring the density, specific gravity, and concentration of liquids in many different industries such as the beer and wine industry, petroleum industry, and in lead acid battery production. As they are typically small and lightweight, digital hydrometers are frequently used as portable devices for on-site measurements. The following article focuses on the setup and use of digital hydrometers.

Development of digital hydrometers

After the development of digital density meters for use in the quality control laboratory in the 1960s, there was an immediate demand for a portable version of these devices for use in the field. Packaging the oscillating U-tube technology into a small, robust model brought a number of challenges, including: 

  • Making the housing robust enough to withstand outdoor use (knocks, spills) without becoming too heavy for portable use
  • Making the whole instrument sealed enough to allow use in hazardous environments and ideally achieve a protection class of IP54
  • Ensuring adequate filling outside of a laboratory environment
  • Having a display that is readable, even in dark or badly lit areas
  • Ensuring the device is light enough for one-handed use and small enough to measure in hard-to-reach places (i.e. from tanks and batteries).
  • Using power supplies independent of plugs e.g. battery power
  • Having a design that makes the instrument intrinsically safe so it can be used in areas where it is needed 

Modern digital hydrometers typically use a W-shaped oscillator made of a borosilicate glass. They have a long filling tube to reach into tanks and containers. Additional features may include: 

  • Gesture control (a way of operating the instrument via hand movements which makes operation easier in dirty environments or when wearing gloves). 
  • An interface for reading RFID tags on containers for quick and traceable sample identification.
  • The possibility of replacing the cell on-site in case of rupture after dropping it.
  • Models which are intrinsically safe and therefore approved for use in hazardous areas (i.e. for measurements on petroleum products, battery acid, and other chemicals).
  • Wireless transfer of measured data via Bluetooth®.

Where are digital hydrometers used?

Typically digital hydrometers are used to check the density, specific gravity, or concentration of:

  • Hot wort
  • Beer
  • Sulfuric acid in lead acid production
  • Wine (during fermentation and before bottling)
  • Sake (during fermentation)
  • Petroleum products like crude oil, gasoline, diesel, lube, and biodiesel
  • Solvents
  • Sodium hydroxide solutions
  • Milk and dairy products
  • Pharmaceuticals

If you are currently carrying out density measurements with a hydrometer or pycnometer you can check how much money and time you would save by using a digital density meter or digital hydrometer.

What is the difference between a hydrometer and a digital hydrometer?


A hydrometer is a basic tool for measuring density which has been used for hundreds of years. Modern hydrometers are made of glass and are immersed into the sample for measurement. The value needs to be read off the scale.

Digital hydrometers

Digital hydrometers are in fact digital density meters in a slightly different form, usually portable, for use in the field. As digital hydrometers have a manual pump to fill the sample from the container and use the oscillating U-tube method of density measurement, results are more accurate, less prone to human error, and more repeatable than with manual hydrometers.



Digital hydrometer

Digital hydrometer