Working Principle and Method of Thermogravimetric Analyzer

　　Thermogravimetric analyzer is mainly composed of several parts such as balance, furnace, program temperature control system, recording system, etc.

　　There are two most commonly used measurement principles, namely the displacement method and the zero-position method. The so-called displacement method is based on the relationship that the inclination of the balance beam is proportional to the mass change, and the inclination is detected by a differential transformer and the like, and automatically recorded. The zero-position method uses the differential transformer method and the optical method to measure the inclination of the balance beam, and then adjusts the current of the coil installed in the balance system and the magnetic field to make the coil rotate to restore the inclination of the balance beam, which is the so-called zero-position method. Since the force applied by the rotation of the coil is proportional to the mass change, and this force is proportional to the current in the coil, it is only necessary to measure and record the change in current to obtain the mass change curve.

　　Thermogravimetric Analyzer Method

　　When the substance being measured sublimates, vaporizes, decomposes gas or loses crystal water during heating, the mass of the substance being measured will change. At this time, the thermogravimetric curve is not a straight line but a decrease. By analyzing the thermogravimetric curve, we can know at what degree the substance being measured changes, and according to the weight loss, we can calculate how much substance is lost (such as crystal water in CuSO4·5H2O). From the thermogravimetric curve, we can know that the 5 crystal waters in CuSO4·5H2O are removed in three steps. Through TGA experiments, it is helpful to study the changes in crystal properties, such as physical phenomena of substances such as melting, evaporation, sublimation and adsorption; it is also helpful to study the chemical phenomena of substances such as dehydration, dissociation, oxidation and reduction. Thermogravimetric analysis can usually be divided into two categories: dynamic (heating) and static (constant temperature). The curve obtained by thermogravimetric test is called thermogravimetric curve (TG curve). The TG curve uses mass as the ordinate, and represents mass reduction from top to bottom; it uses temperature (or time) as the abscissa, and represents temperature (or time) increase from left to right.