TGA instruments can be divided into two general types: vertical and horizontal balance. Vertical
balance instruments have a specimen pan hanging from the balance (TA Instruments, etc) or
located above the balance on a sample stem (Netzsch). It is necessary to calibrate these
instruments in order to compensate for buoyancy effects due to the variation in the density of the
purge gas with temperature, as well as the type of gas. Vertical balance instruments generally do
not have reference pan and are incapable of true DTA or DSC measurements (Netzsch being an
exception).