The Stanford Research model QCM100 is a low cost quartz crystal microbalance system designed for real-time mass and viscosity measurements in processes occurring at or near surfaces, or within thin films. It comes with controller, oscillator electronics, crystal holder, and three quartz crystals. An external frequency counter and precision voltmeter (not included) are needed to complete the QCM measurement setup. The QCM100 measures the resonant frequency and resistance of an AT-cut quartz crystal. The resonant frequency changes as a linear function of the mass of material deposited on the crystal surface. The resistance at resonance changes with the viscoelasticity of the material (film or liquid) in contact with the crystal’s face.