Thermogravimetric Analyzer (TGA)

Overview

A thermogravimetric analyzer answers a simple question with great precision: how does a material's mass change as you heat it? Drive the temperature up on a programmed ramp and watch the weight, and the sample tells its story, moisture boiling off, a polymer decomposing, a carbonate releasing carbon dioxide, a metal oxidizing. Each event shows up as a step in the mass curve at a characteristic temperature, so TGA is used to measure composition, thermal stability, filler content and decomposition kinetics across plastics, pharmaceuticals, minerals and fuels.

The challenge is weighing a sample to a fraction of a microgram while it sits inside a furnace climbing past a thousand degrees, swept by flowing gas. The instrument is built around solving exactly that.

How it works

The sample hangs from the Ultra-Microbalance, a null-balance design. The Balance Beam tries to tip as the sample's weight changes; a Optical Position Transducer senses the slightest tilt and a Tare / Restoring Motor applies just enough restoring force to hold the beam level. The current that motor needs is the measure of mass, good to about a tenth of a microgram.

Around the sample sits the Programmable Furnace. A wound Heating Element and a thermocouple under PID control raise the temperature along the programmed ramp, while insulation and the furnace tube hold the heat steady around the pan. For unattended runs the Sample Pan Autosampler picks pans from a carousel and places each on the balance hangdown in turn.

Throughout, the Purge Gas Flow System system sweeps a purge gas, inert nitrogen or reactive air, past the sample, switching gases through valves and metering the rate with a mass flow controller so evolved gases are carried away and don't settle on the balance. The Control & Computer runs the temperature program and the gas and balance systems together and plots mass against temperature, the thermogram the analyst interprets. The Instrument Housing shields the delicate balance from drafts and the operator from the hot furnace.