Refractometer and hydrometer are two types of instruments for measurement. Here are their brief introduction.

Refractometer is an optical device measuring the refractive index to determine the mixture concentration. It can analyze the solution’s purity from the amount of dissolved substances. The working principle is that as light passes through the solution, it will deviate and form a refraction angle. The angle depends on the amount of solids dissolved in the solution.

Hydrometer is an instrument to measure the relative density of the liquid. The measurement is according to Archimedes’ principle. It works by the submerged part of the solid displacing its equal weight liquid. The sinking depth of the hydrometer is negatively correlated with the density of the liquid.

They have similarities and a lot of differences in many aspects. Now, this post will mainly talk about the comparison between them and provide some suggestions for using and purchasing a hydrometer or refractometer.

hydrometer vs refractometer

Similarity of refractometer and hydrometer

Hydrometer and refractometer can both measure the concentration or density of liquids. And they need to be calibrated by using a calibration solution or calibration fluid. Hydrometers and traditional refractometers have a scale to show the result. And they both can measure a wide range of solutions besides water. In addition, they can be both used in different industries like brewing and food. In the production process, refractometer and hydrometer are both commonly used instruments. Besides, they both can take measurements during the fermentation process. So, it is easy to monitor the beer brewing. And then they can determine when the home brewing process has finished. It aims to get high-quality products efficiently.

Difference between hydrometer and refractometer

Hydrometer can only measure liquid solutions. But refractometer can measure liquid and semi-solid objects at the same time. Hydrometers are divided into different types according to the liquid they measure. Refractometers are not limited by types of liquid. You only need to consider the form and accuracy when using it. In a word, refractometers are more convenient and widely used than hydrometers. refractometer vs hydrometer The fundamental difference is that they have different working principles. A refractometer works based on the principle of refraction. But a hydrometer works according to the principle of buoyancy. Here are other important differences between these two essential tools.

Refractometer and hydrometer have different readings

Refractometer uses 20℃ as the standard temperature. It measures the percent sucrose in the solution and its unit is °bx. And it usually represents the sugar content of the liquid. Hydrometer uses 15℃ as the standard temperature. It measures the depth of the hydrometer immersed in the solution. And it calculates the concentration of the solution from the depth and density of the liquid. The unit is g/cm³ and it displays gravity readings.

Hydrometer and refractometer need different sample sizes

A hydrometer needs a large sample size for measurement. For measuring the specific gravity, larger-sized samples need to be extracted from the testing liquid than refractometers. Thus, every time you measure, there will be a significant waste of liquid.

However, a refractometer has an ideal sample size of a few drops of wort or beer. It means that you will not waste too much on the measurement. And you don’t need to extract samples several times. Multiple operations may result in solution contamination.

If you don’t want to waste a lot when measuring the amount of dissolved solids, you’d better use a refractometer. Because the sample size required for measurement is only a few drops.

Refractometer and hydrometer with different temperature requirements

Hydrometers must be adjusted according to temperature. Because it will operate at a specific temperature. So, changes in liquid temperature require adjustments to the results. The higher the temperature of the liquid, the lower the density. Thus, the temperature affects the results if you measure the sugar content or sugar levels. If the liquid is at room temperature, you may get an accurate sample reading from the device. But the hotter the liquid, the less dense it is. Therefore, it may provide you with an inaccurate reading if the sample is too hot. On the other hand, refractometers may be better than that. They need small sample sizes, so the sample is cooled much faster. Besides, some refractometers have temperature compensating functions. Thus, it allows small differences in temperature. And the refractometer readings will not be greatly influenced.

Refractometer and hydrometer in different application fields

A hydrometer displaces the testing liquid to show the readings usually by measuring the specific gravity brix. A refractometer uses light refraction to determine the amount of solids dissolved in a liquid. These two instruments both can measure a wide range of substances in different fields. But they vary a lot for the measurements in different application fields. The main differences between them are as follows.

brix refractometer vs hydrometer

Brix refractometer vs hydrometer:

Different scales including specific gravity, degrees brix, degrees Baume and degrees Plato are used in different industries. For quality control reasons, brix measurement is usually taken in the food industry. For example, soft drinks, fruit juices, and foods with high sugar levels. Because accurate readings of brix are of great help for quality control. The brix value can be mainly measured by a brix refractometer or hydrometer. But these brix meters do have some differences.

A hydrometer needs adjustments to measure the sugar content at the beginning. But for a refractometer, adjustment is unnecessary due to its testing method. Then, the hydrometer requires a larger sample volume than the refractometer. Besides, a brix meter refractometer is easier to operate and the measurement process is more rapid. In addition, digital brix refractometers usually have a wider brix range than hydrometers.

Refractometer vs hydrometer coolant:

Coolant hydrometer or refractometer measures the concentration of glycol based antifreeze. They can determine the freezing point of the cooling system. For a hydrometer, coolant is first drawn into it and a needle will float to show the antifreeze point.

Hydrometers are only available for coolants and antifreeze containing ethylene glycol. And it cannot measure propylene glycol. The measuring range of ethylene glycol is from -51 ° C to 0 ° C. As a result, it can determine whether the solution is properly mixed to avoid freezing.

Another device to determine fluid properties is the refractometer. It can work with ethylene glycol and propylene glycol based coolant. The refractometer is a relatively cost-effective and accurate way without many limitations. Refractometer measures and displays the reading immediately using only a small sample. Refractometers use prisms and magnifiers to measure small variations in the speed of light passing through the liquid. Then you can get the concentration and freezing point of the fluid. So, it is an ideal tool for measuring water-based solutions like coolant.

Homebrew refractometer vs hydrometer (alcohol refractometer vs hydrometer):

homebrew refractometer vs hydrometer Homebrew refractometer and hydrometer are two common types of instruments measuring the amount of solids dissolved in the beer or wine. Thus, they are useful for home brewers on a brew day. But they are different tools that work in different ways. They can predict the alcohol content in the finished beer or wine.

Hydrometer vs refractometer beer:

In home brewing industry, the dissolved substance we measure is sugar. Generally speaking, this sugar is from malt extract, whole-grain malt, or both. The content of dissolved sugar in wort can be measured as brix, degrees Plato, or specific gravity. Most home brewers primarily take specific gravity as the scale. However, brix is usually the scale for the refractometer.

Compared to refractometers, a homebrew hydrometer is a low-cost tool for measuring alcohol content. A hydrometer measures the specific gravity of the wort or beer essential for brew beer production. But for each refractometer reading, you only need a few drops of sample to work before and after the brew day. So, you don’t need to waste too much wort during the brewing process. In addition, it is unnecessary to perform temperature compensating. And calibration is usually necessary before specific gravity measurements. It aims to ensure the accuracy of the refractometer readings.

Hydrometer vs refractometer salinity:

To maintain a good environment for fish and corals, it is necessary to monitor the salinity (salt level) of the fish only or reef aquarium. In the saltwater aquarium hobby before, people may use a floating glass hydrometer to measure the salinity or specific gravity. Nowadays, salinity measuring is typically done by a refractometer and swing arm hydrometer. These two essential tools can obtain the salt level or gravity reading of a water sample. But they work so differently.

Refractometers measure the refractive index of the water sample. However, hydrometers measure the density of the liquid directly. So, the salinity or specific gravity brix measurement result of the former is more accurate than the latter. Besides, many refractometers have an automatic temperature compensation system to suit different temperatures. As a result, refractometers are more popular salinity measuring tools. A small shortcoming of the refractometer is the calibration process. Because calibrating the device with distilled water is easy but also troublesome.

In general, the refractometer is better than the swing arm hydrometer. Prices of the former may be higher, but the performance and the accuracy are much higher than the latter.

How to use a refractometer and hydrometer?

For hydrometers, sanitize the tool to avoid cross-contamination first. You need a large sample to take hydrometer measurements. Then, fill the test jar with enough samples that can make the hydrometer float. After that, you need to place the hydrometer in the test jar and rotate it rapidly to remove air bubbles. Once the device is stable, the point where the top of the liquid reaches is the reading required. To get an accurate reading, the temperature of the sample liquid must be 60° F. If it is not at 60° F, you will get an inaccurate reading requiring adjustments according to automatic calculators online. After the hydrometer measurements, discard the sample that is no longer useful.

As for digital refractometers, the process is much easier. First, place a few drops of calibration fluid on the tested plate. It aims to get the refractometer calibrated properly before proceeding. Then, press the button in the center to calibrate the refractometer. After that, wipe off the calibration solution and fill the plate with a few drops of the liquid sample. Next, press the button again and the screen will display the reading within 2 seconds. At last, feel free to rinse the refractometer with fresh water or distilled water for the next use.

difference between hydrometer and refractometer

FJD refractometers all have the function of automatic temperature compensation. So you can ignore the effects of temperature and get accurate readings. Besides, FJD digital refractometers can measure many kinds of substances for their wider brix range. The products include handheld refractometer, ATC refractometer, and maple syrup refractometer.

How to choose a refractometer and hydrometer?

There is a difference between hydrometer and refractometer in many aspects. You can consider the hydrometer as a basic necessity for its characteristics. To measure more accurately for better results, then you may want to purchase a refractometer.

If you brew beer at home, you need to measure the original gravity of the wort unfermented first. Next, you will also record final gravity fg readings after finishing brewing beer at home. Then you can calculate the ultimate alcohol by volume of the finished beer. Compare with original gravity and final gravity fg readings in the fermentation process, you will find the former is always greater than the latter. And the alcohol by volume is the result of the former minus the latter and divided by 0.0075.

For a well-experienced brewer, purchasing a refractometer can be a valuable investment. Because it comes with high accuracy and automatic temperature compensation. In addition, FJD digital refractometers all come with a mobile App. The App has built-in models for measuring a wide range of substances including fruit, coffee, beer or wine, antifreeze, and maple syrup.

In a word, both two types of essential tools for brix and specific gravity measurements are imperfect. The hydrometer and the refractometer have their own advantages and disadvantages. You can choose the one that fits you most.

refractometer and hydrometer