# What is the difference between a hydrometer and a densitometer? How to read the mud hydrometer?

What is the difference between a hydrometer and a densitometer? How to read the mud hydrometer?

There are many instruments that are often used in life. We often have thermometers, buoyancy meters, and viscometers. There are many instruments that we don’t use, but they are very useful, such as Petroleum hydrometers and densitometers. For the pycnometer and the density meter, many friends are always confused. I don’t know where the difference is before, so the following small series will tell you what is the difference between the hydrometer and the densitometer? How to read the mud hydrometer?

What is the difference between a hydrometer and a densitometer?

Many people often ask a question: What is the difference between density and weight?

So I wrote the definitions of density and specific gravity.

Density refers to the weight per unit volume of a substance.

D = W / V, that is, D = Wa / (Wa – Ww) is usually expressed in g / cm3.

Wa: The weight of the sample in the air.

Ww: The weight of the sample in the water.

Definition of specific gravity

1. Ratio of material density to 4°C pure water density SG=material density/4°C pure water density
2. The ratio of the weight of an object in the air to the volume of the object.

Example: If the weight of the object in the air is P grams, the weight of the object at 4 ° C is P1 gram SG = P / (P-P1)

For liquid or solid refers to a certain temperature, density under pressure and pure water in the standard

The ratio of the maximum density under air pressure (density at a temperature of 3.98 ° C is 999.972 kg / m 3 )

By gas is meant the ratio of the molecular weight of the gas to the molecular weight of the air (28.9644).

The specific gravity varies with temperature and pressure under normal conditions. The proportion is abbreviated as SG.

In general, we regard density and specific gravity as the same concept, so our density tester can also be called: density balance, specific gravity balance, density meter, hydrometer, and so on.

Density is defined as the mass per unit volume and the unit of density. The specific gravity is defined as the ratio of the mass of a substance at a certain temperature to the mass of the same volume of water at 4 degrees Celsius (so called the specific gravity, the mass is commonly called “weight”), and it is apparent that the specific gravity has no unit. Therefore, the physical meaning of the two is completely different, but the density of water at 4 degrees Celsius is almost very accurate 1g/cm3, so when the density is g/cm3 or equivalent kg/dm3, the values ​​are the same (using When other units are not equivalent, the values ​​are different).

How to read the mud hydrometer?

1. Remove the cup lid and fill it with the sample of drilling fluid to be tested. If the air is immersed in the drilling fluid, gently tap the drilling fluid cup until the bubble overflows the cup (if the cement is required to swing the cement slurry 25 times)
2. Reattach the lid and rotate straight and tight to allow excess drilling fluid and air to be squeezed out of the middle hole of the lid.
3. Wipe off the excess drilling fluid on the outer surface of the scale and the lid of the cup.
4. Align the main blade of the scale body with the knife edge and place it on the support base.
5. Move the weight near the main blade, then slowly move the weight to the right to maintain the horizontal balance of the lever (the balance of the lever’s main ruler, whether the horizontal bubble can be used to measure balance).
6. Reading: The engraved line on the left side of the weight is the specific gravity of the measured drilling fluid.