What is a Hydrometer? Its Function, How It Works, and Its Uses

A hydrometer is a measuring instrument used to measure the specific gravity of liquids and is often used in the automotive field. For those of you who are not familiar with this measuring instrument, you need to know a complete review of what a hydrometer is as follows. 

What is a Hydrometer? 

As previously explained, a hydrometer is a measuring instrument used in the automotive field, specifically to measure the specific gravity or density of electrolyte liquid in vehicle batteries or wet batteries. The hydrometer itself has a unit of g/cm3 similar to the units used to measure kerosene, gasoline, or diesel fuel. 

Function of the Hydrometer

The hydrometer has a vital function in the automotive world, namely measuring the density or specific gravity of electrolyte liquid in wet battery batteries. With a hydrometer, car owners or mechanics can determine whether the condition of the electrolyte liquid in the wet battery is good or not. The hydrometer itself has several parts, and each part has a different function but remains interconnected. The parts are as follows. 

1. Float (container)

This part serves as an indicator of the measurement results. The float is divided into three rows accompanied by different colors and numbers to indicate the quality of the measurement results.

2. Suction bulb/pipette

This part functions as a suction for the electrolyte liquid from the battery so that it can be inserted into the hydrometer. 

3. Pickup tube 

This part serves as the entrance and exit for the electrolyte liquid from the battery to the outer tube. 

How the Hydrometer Works 

The hydrometer has a simple working mechanism. This measuring instrument will work when the pipette part is pressed. After being pressed, the pipette will suck or draw the electrolyte liquid from the wet battery. Then the liquid will enter the pickup tube, and the float will float while showing the measurement result of the specific gravity of the electrolyte liquid. 

How to Use a Hydrometer 

There are several ways to use a hydrometer that you need to know. The steps are as follows. 

1. Prepare the hydrometer and ensure it is clean

Before taking measurements, you should first prepare the hydrometer that you will use. Make sure the hydrometer is clean.

2. Calibrate the hydrometer

Next, you need to recalibrate the hydrometer. Ensure that the calibration results show a value of 1 kg/cm3 or are in the clear color area. 

3. Start measuring

After the calibration process is complete, open all the caps on the wet battery of the car. Then take measurements by pressing the pipette part of the hydrometer and releasing it slowly so that the electrolyte liquid from the wet battery is sucked into the pickup tube and the float floats while showing the measurement result. 

4. Read the measurement results

Next, you just need to read the measurement results to see if the quality of the electrolyte liquid in your car's wet battery is still good or not. To determine whether the measurement results are accurate, you need to understand the meaning of the hydrometer colors as follows. 

• Clear: specific gravity of the electrolyte liquid at 1 or neutral. 
• Red: specific gravity of the electrolyte liquid is between 1.100 and 1.220, indicating that the battery needs to have sulfuric acid or distilled water added.
• White: specific gravity of the electrolyte liquid is between 1.225 and 1.250, indicating that the battery is in normal and sufficient condition (no need to add sulfuric acid or distilled water). 
• Green: specific gravity of the electrolyte liquid is between 1.260 and 1.280, indicating that the electrolyte liquid in the wet battery is in good condition. 

5. Repeat the measurement

To ensure that the measurement results are accurate, you can repeat the measurement two or three times. Usually, the electrolyte liquid in a quality wet battery has a specific gravity value according to the standard mass (weight) of the battery electrolyte, which is between 1.260 and 1.280. 

Thus, here are some methods you can follow when measuring the specific gravity of electrolyte liquid. If you are still confused, you can have the measurement done at a Daihatsu official workshop.