Inexpensive but accurate driving circuits for quartz crystal microbalances

The quartz crystal microbalance (QCM) is a common technique which finds a w ide variety of applications in many different areas like adsorption, cataly sis, analytical chemistry, biochemistry, etc., and more generally as a sens or in the investigation of viscoelastic films. In this article we describe some driving circuits of the quartz which we have realized and tested in ou r laboratory. These can be assembled with standard components which can be easily found. Their performance, in some cases, is as good as that of the m uch more expensive frequency modulation technique employed in very precise QCM measurements and which requires high-quality commercial radiofrequency generators and amplifiers. (C) 1999 American Institute of Physics. [S0034-6 748(99)01001-1].