Difference Between Hydrometer And Hygrometer

In our daily lives, several scientific technologies are utilized to quantify the density of components around us. Hydrometers and hygrometers are two examples of such instruments. A hydrometer measures the density of a liquid using Archimedes’ principle of flotation, whereas a hygrometer detects the degree of humidity and moisture in the atmosphere.

Hydrometer vs Hygrometer

The main differences between a hydrometer and a hygrometer are that of their measuring principles and working principles. The measuring principle of a hydrometer is measuring the density of a liquid and it works on the principle of flotation. A hygrometer measures humidity and moisture in the atmosphere and works on several different principles.

Hydrometer vs Hygrometer

A hydrometer is an instrument that is used to determine the density of gravity of a liquid. A hydrometer’s measuring principle is measuring the depth of water using the Archimedes principle of flotation. The word origin of hydrometer lies in the Greek word hydro which means water. The hydrometer was invented by a Greek scholar named Hypatia.

A hygrometer is used to measure humidity or moisture content in the surrounding atmosphere.  The word origin of hydrometer lies in Greek. The hygrometer is derived from the Greek word Hygros meaning wet or moist. All hygrometers work on different principles. The hygrometer was invented by Leonardo Da Vinci.

Comparison Table Between Hydrometer And Hygrometer

Parameters of ComparisonHydrometerHygrometer
DefinitionA hydrometer is an instrument used to determine the specific gravity, or relative density, of a liquidA hygrometer is a device that measures the humidity in a specific volume
Inaccuracy/AccuracySimpler to manage the accuracyDifficult to maintain accuracy and can provide inaccurate measurements
Factors influencing accuracyTo ensure accuracy, certain criteria like temperature, cleanliness, and correct immersion must be considered.To assure precision, several parameters such as pressure, temperature, mass, and electrical charge must be standardized.
Thermometer built-in Features built-in thermometers A built-in thermometer is not always employed
InventorInvented by Hypatia Invented by Leonardo Da Vinci

What is Hydrometer?

A hydrometer is an instrument that utilizes buoyancy to assess the relative liquid limit. They are frequently validated and graded with the use of one or more indicators, such as specific gravity. A hydrometer is normally constructed from a walled hollow glass tube with a wider lower quarter for buoyancy, a counterbalance such as lead or mercury for stabilization, and a slender stem with graded graduations for measurements.

The sample liquid is placed in a tall vessel, usually a weighing cylinder, and the hydrometer is progressively plunged into the liquid until it reaches the surface. The relative density is determined by the height at which the liquid’s surface reaches the stem of the hydrometer. Any combination of scales anywhere along the stem of a hydrometer can correspond to density-related factors. 

A hydrometer is used to calculate the density (fluffy texture) of milk, a saccharometer to assess the thickness of glucose in a fluid, and an alcoholometer to measure higher concentrations of alcohol in drinks. The hydrometer works on Archimedes’ principle, which says that a solid submerged in a fluid is buoyed by a pressure that is directly proportionate to the weight of the fluid displaced by the drowned section of the suspended material. The deeper a hydrometer of a particular weight dips, the lesser the density of the fluid; the stem is regulated to provide a numerical measurement.

What is Hygrometer?

A hygrometer is a device that monitors the amount of water vapor in the air, soil, or other confined areas. Humidity meters frequently rely on other measures, such as heat, tension, quantity, or an electromechanical alteration in a component when moisture is consumed.

These measured values can be used to calculate humidity using calibration and computation. Modern electronic gadgets use the temperatures of precipitation (called the dew point) or fluctuations in electronic capacitance or susceptibility to detect humidity swings.

Around 1480, Leonardo da Vinci built a crude hygrometer. The optimum quantity of water vapor that can be maintained in each amount of air (saturation) changes significantly with temperature; cold air can contain less water per unit volume than hot air. The temperature may influence humidity levels.

Hygrometers are used in labs, salons, humidors, and galleries, in addition to conservatories and businesses. They are also used to care for wooden stringed instruments like piano, guitar, and violin, which can be damaged by excessive humidity levels.

In wildfires, hygrometers are useful because the lower the percentage of the humidity, the quicker the fuels burned. Hygrometers are used in residential settings to help with humidity control. Hygrometers are frequently employed in the painting business since the application of paint can be particularly sensitive to humidity and dew point.

Main Differences Between Hydrometer And Hygrometer

  1. A hydrometer is an instrument that is used to determine the density of gravity of a liquid whereas a hygrometer is used to measure humidity in a specific volume.
  2. A hydrometer is simpler to manage accuracy, whereas a hygrometer is more difficult to maintain accuracy and provides erroneous measurements below the freezing point.
  3. To ensure accuracy in hydrometer, certain criteria like as temperature, cleanliness, and correct immersion must be considered. Whereas to assure precision in hygrometer several parameters such as pressure, temperature, mass, and electrical charge must be standardized.
  4. Advanced hydrometers feature built-in thermometers that allow them to readily measure the temperature of the liquid, whereas a built-in thermometer is not always utilized in hygrometers but is required for relative humidity calculations.
  5. The hydrometer was invented by a Greek scholar names Hypatia and the hygrometer was invented by Leonardo Da Vinci.


Hydrometers are required to demonstrate the accuracy of specific gravity and density of liquids, whereas hygrometers are required to detect humidity levels. When humidity levels are too high, it causes lethargy, weariness, and respiratory illnesses. On the other side, if humidity levels are too low, wood furniture, musical instruments, and other items will deteriorate.

As a result, mankind will be able to preserve its equilibrium. Both devices, however, require temperature calibration and maintenance to provide reliable results. There will come a day when technological breakthroughs will give us better measuring precision. Both Hypates and Da Vinci would have been pleased to watch their prototypes in the process of evolution up until that point.

The accuracy of a hydrometer is determined by three factors: cleanliness, temperature, and appropriate immersion. Both the hydrometer and the tank or cylinder that holds the liquid to be tested must be clean. As a result, the liquid rises equally, providing an accurate readout. Furthermore, the temperature of the liquid and the surrounding environment should be comparable.

As a result, density changes are avoided. As a result, the jar containing the liquid should be large enough to accommodate the immersion of the hydrometer.

The precision of hygrometers, on the other hand, is difficult to maintain. Temperature, pressure, electrical change, and mass must all be taken into account. Below the freezing point, conventional hygrometers are inaccurate.


  1. https://aip.scitation.org/doi/abs/10.1063/1.1770616
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