Dilatometer

Dilatometer

A dilatometer is a device that measures the change in volume caused due to a chemical or a physical process in a substance. A good example will be a mercury-in-glass thermometer which is the most basic application of the dilatometer. In the mercury-in-glass thermometer, when the thermometer comes in contact with a human body, the volume of the mercury starts to expand due to a rise in the temperature.

The dilatometer works on the principle of volume expansion when there is a change in the surrounding area’s temperature.

Types of Dilatometer

There are multiple types of dilatometer available; a few of them are listed below:

Capacitance Dilatometer

A capacitance dilatometer consists of a parallel plate capacitor, whose one plate is stationary while the other is movable. When a sample is kept between this plate, it expands due to a change in its volume, which increases the gap between the two plates. Due to this change in the gap, the capacitance decreases. This happens because capacitance is inversely proportional to the gap between the plates. A capacitance dilatometer is very sensitive and can measure a change of about ten picometers.

Connecting Rod

The connecting rod dilatometer is also known as a Pushrod dilatometer. The process is carried out in a furnace in this dilatometer. The substance is kept between the two rods, and when the furnace is started due to the heat, the substance begins to expand. This expansion pushes the rod back, and the measurement of the expansion is carried out. The issue with this process is that when the furnace is started with heat, the rod also begins to expand, therefore, while calculating the expansion. The expanded length of the rod is also needed to be reduced from the measurement.

High Resolution-Laser Dilatometer

The High resolution-laser dilatometer works on the principle of the Interferometer. These types of dilatometers are the most accurate type of dilatometer available, therefore are mostly used where there is a need for high accuracy. The High Resolution-Laser Dilatometer can measure a change of up to 10th of a picometer. Therefore, it is highly precise. This type of dilatometer does not need any calibration.

Optical Dilatometer

An optical dilatometer can measure the change in the volume of a substance within the temperature range of 25 degree C to 1400 degree C. The optical dilatometer has two cameras, and therefore, the volume expansion is done without being in contact with the substance. The camera takes the image of the substance or specimen as a function of the temperature. The resolution of the image is ±70 micrometer per pixel.

Usage of Dilatometer

Although, a dilatometer has a lot of applications. A few are:

• To investigate martensite transformation in the manufacture of metallic alloys.

• Glasses, ceramic goods, composite materials, and plastics are examples of compressed and sintered refractory compounds.

• For monitoring the course of chemical reactions in chemical labs.

• In the realm of food science, it is used to calculate the solid fat index of food oils, butter, ghee, etc.

• For determining the thermal expansion of various materials.

Conclusion

A dilatometer is a device that measures the expansion of the volume of a substance due to physical or chemical processes. There are multiple types of dilatometer available, but the four most commonly known dilatometers are Capacitance Dilatometer, Connecting Rod or Push Rod Dilatometer, High Resolution-Laser Dilatometer, and Optical Dilatometer.