Difference WikiPhysics

Difference Between Hydrometer and Hygrometer

Main Difference

The main difference between Hydrometer and Hygrometer is that Hydrometer calculates the relative gravity or the density of a particular fluid, whereas Hygrometer calculates the moisture present in the surroundings.

Hydrometer vs. Hygrometer

A hydrometer is a means that measures the specific gravity of any particular liquid, which is a sign of the density of a liquid; on the other hand, a hygrometer is a device which is correctly used to measure the humidity, i.e., the number of water vapors present in the atmosphere.

The word hydrometer comes from the Greek word hydro means water (as in hydrated and hydrogen); on the flip side, the word hygrometer is derived from Greek for wet or moist. The hydrometer was initially invented by a Greek scholar Hypatia in the early 5th century, whereas Leonardo da Vinci first invented the hygrometer in the early 15th century.

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Most of the time, the hydrometer works through measuring how much an object sinks in a liquid; on the contrary, there are many different types of hygrometers present, and each type makes use of a diverse principle to measure the humidity in the atmosphere. The purpose of the instrument categorizes a hydrometer and the context of use; on the other hand, the hygrometer is classified by different methods that are used to measure humidity.

The hydrometer is more comfortable to ensure accuracy; on the flip side, the hygrometer is usually challenging to maintain accuracy and gives inaccurate measurement below the freezing point. Some factors, such as temperature, cleanliness, and proper immersion, need to be accounted for to maintain the accuracy of the hydrometer. In contrast, some considerations, for example, pressure, temperature, mass, and electrical charge, are needed to standardize to ensure the accuracy of the hygrometer.

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Comparison Chart

HydrometerHygrometer
A device that calculates the density or specific gravity of a liquid by moving in the liquid is known as a hydrometer.A device that measures the humidity, the amount of water vapor exist in the air, is known as a hygrometer.
Measurement
Measures the specific gravity of a particular liquid which is a sign of the density of a liquidMeasure the humidity, i.e., the number of water vapors present in the atmosphere
Working Principle
Most of the time, the working principle works through measuring how much an object sinks in a liquidThere are many different types, and each work on the specific law and each type makes use of an altered principle to measure the humidity in the atmosphere
Derivation
The word comes from the Greek word hydro means water (as in hydrated and hydrogen)The term is derived from Greek for wet or moist.
Invented By
Initially invented by a Greek scholar Hypatia in early 5th centuryFirst created by Leonardo da Vinci in the early 15th century
Categorized By
Categorized by the purpose of the instrument and the context of the useClassified by the use of the different methods which are used to measure the humidity
Accuracy/ Inaccuracy
Easier to ensure accuracyUsually difficult to maintain accuracy and gives inaccurate measurement below freezing point
Factors for Maintaining Accuracy
Some factors such as temperature, cleanliness, and proper immersion need to be accounted to maintain the accuracySome factors for example pressure, temperature, mass, and electrical charge are required to standardize to ensure the accuracy
In-Built Thermometer
Advanced hydrometers have built-in thermometers to measure the temperature of the liquid easilyA built-in thermometer is not necessarily used but a requirement for a relative humidity calculations
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What is Hydrometer?

An instrument that is used to measure the specific gravity of a liquid of a particular liquid is known as the hydrometer. This instrument is very often used to measure the density of alcohol in drinks and also to calculate the dilution level in the milk. The specific gravity in hydrometer is a capacity that tells how much a liquid is compact as compared to the density of water.

The hydrometer works on flotation’s principle. Whenever an object is dipped in a fluid, it moves a volume of liquid, which is primarily equal to the amount of that specific object which is present inside the fluid.

A liquid applies a force on the object in an upward direction, known as the upthrust, which is primarily equal to the weight of the fluid, which has been moved by the object; this is according to the principle of flotation. Whenever the upthrust is equal to its weight, the object continues to float. In other words, when an object floats on the surface, it dislodges an amount of fluid that contains weight equal to the weight of the object.

What is Hygrometer?

An instrument that typically measures the humidity is known as the hygrometer. A hygrometer consists of many types that use different mechanisms to measure the moisture.

A type of hygrometer in which a piece of hair is connected to the needle, known as hair tension hygrometer. Whenever the humidity is high, the hair lengthens, and when humidity is low, it again shortens. The needle from which the piece of hair is attached can then move along a scale to specify the humidity.

Another type of hygrometer is a psychrometer. The psychrometer contains two thermometers: one is known as a wet-bulb thermometer because its bulb is covered with a damp cloth, and the second is a dry-bulb thermometer as its bulb is open to the air. The wet-bulb thermometer measures the cooler temperature because the evaporation of water occurs from the damp cloth.

Another type of hygrometer is an electrical hygrometer, which calculates the humidity by measuring the variation in resistivity in some circuit components as the change occurs in humidity. A hygrometer is widely used in humidors, museums, incubators, industrial spaces, greenhouses, saunas, coating industry, etc.

Key Differences

  1. A hydrometer is considered an instrument which is used to measure the relative density of a liquid or to measure the specific gravity. At the same time, a hygrometer is also considered an instrument which is used to measure the humidity of air in a given volume of the container.
  2. In hydrometer, the word hydro comes from the Greek word, which means water, hydro (as in hydrogen or hydrated); on the other hand, in hygrometer, the word hygros means wet or moist comes from the Greek word.
  3. Cleanliness, temperature, and proper immersion are some factors which are needed to be accountable to maintain the accuracy of a hydrometer. In contrast, temperature, pressure, electrical charge, and mass are leading factors that are required to be consistent to ensure the accuracy of a hygrometer.
  4. It is relatively easy to confirm the accuracy of a hydrometer. On the other hand, it is tough to maintain the accuracy of a hygrometer and becomes inaccurate below the freezing point.
  5. Categorization of the hydrometer is done by concerning the specific time to be used and the purpose of the measurement; on the other hand, the hygrometer is divided into categories by the method used to measure the required humidity value.

Conclusion

The above discussion concludes that the hydrometer is used to measure the relative density of a liquid; in contrast, a hygrometer is used to measure the humidity present in the atmosphere.

Harlon Moss

Harlon currently works as a quality moderator and content writer for Difference Wiki. He graduated from the University of California in 2010 with a degree in Computer Science. Follow him on Twitter @HarlonMoss