Contactless weighing under extreme conditions 

Magnetic suspension balances allow us to obtain extremely precise measurements of the force and mass changes which act on samples under controlled environments pressure, temperature, aggressive atmospheres etc.). These measurements enable us to determine transport quantities and state quantities quickly and accurately,  sorption, diffusion, surface, tension, density), to study chemical reactions (corrosion, decomposition, pyrolysis etc.) and to investigate production techniques (polymerisation, coating, drying etc.).  

Application

Besides being applied to fundamental research work and material testing these measurements are also used to design and optimize a great number of industrial operations, e.g.:

Sorption measurements:

-                     Exhaust gas cleaning

-                     Soil detoxication

-                     Foodstuff manufacturing

-                     natural gas and hydrogen storing and/or cleaning

-                     plastic fabrication

-                     supercritical fluid extraction

Thermogravimetry:

-                     gasification of coal

-                     garbage incineration

-                     material synthesis

Density measurements:

-           PVT-behaviour measurement

Our magnetic suspension balances make it possible to weigh samples contactlessly under nearly all measuring conditions. Instead of hanging directly at the balance (conventional gravimetric apparatus) the sample to be investigated is linked to a so called "suspension magnet". An electromagnet, which is attached at the underfloor weighing hook of a balance, maintains the freely suspended state of the suspension magnet via an electronical control unit.

Using this magnetic suspension coupling the measuring force is transmitted contactlessly from the measuring chamber to the microbalance which is located outside the chamber under ambient conditions. Consequently, this set up eliminates almost all restrictions which are inherent to conventional gravimetric measuring instruments, and a general application of this extremely accurate and direct measuring method in various scientific research and development fields becomes both possible and obvious.

The application range for standard versions of the magnetic suspenion balance is given here. Special versions of the magnetic suspension balance considerably extend this measuring range.

The accuracy of the suspension balances is higher than that which can be achieved by manual weighing with a commercial balance alone. This results from an optimum control of the free suspension state, the gentle coupling and decoupling of the measuring load by the suspension coupling itself, the zero point correction and the calibration of the balances. The latter leads to a measuring accuracy with a 2 digit reproducibility which can hardly be bettered, particularly when long term measurements are carried out. 

 Weighing of a 20 g stainless steel calibrated weight in vacuum for 12 hours using a standard magnetic suspension balance with a resolution of 0.01 mg. (Measured deviations have been applied to the starting value in mg.)

Weighing of a 3 g stainless steel calibrated weight in vacuum for 100 hours using a standard magnetic suspension balance with a resolution of 1 g. (Measured deviations have been applied to the starting value in g.)