microbalance n : balance for weighing very small objects
A microbalance is an instrument capable of making precise measurements of weight of objects of relatively small mass: of the order of a million parts of a gram. In comparison, a standard analytical balance is 100 times less sensitive i.e. it is limited in precision to 0.1 milligrams. Microbalances are generally used in a laboratory as standalone instruments but are also incorporated into other instruments, such as thermogravimetry, sorption/desorption systems, and surface property instruments.
Any weighing device needs to provide repeatability and accuracy of measurement. Repeatability is the instrument's ability to display the same value for a given sample at different times. Accuracy is the instrument's ability to show the true weight of a sample within the repeatability of the instrument. In order to maintain these properties, an instrument has to be calibrated. This is usually performed by adjusting the instrument give the correct reading for a known standard weight (referenced to NIST). It is the precision of the microbalance that distinguishes it from other weighing devices.
Quartz crystal microbalance is a very sensitive mass deposition sensor based on the piezoelectric properties of the quartz crystal. This technique uses the changes in resonance frequency of the crystal to measure the mass on the surface because the resonance frequency is highly dependent on any changes of the crystal mass. A quartz crystal microbalance is capable of measuring mass deposition down to 0.1 nanograms.
microbalance in German: Mikrowaage