NEW DESIGN FOR QCM SENSORS IN LIQUIDS

The use of quartz-crystal microbalance (QCM) sensors in liquids for an alytical purposes requires a well-designed transducer. Therefore a the oretical model is necessary to characterize the influence of liquid pr operties like density, viscosity, conductivity and dielectric behaviou r. The high damping of the liquid loading results in a large loss of t he quartz-crystal quality factor. Special electronics and a suitable s ensor cell are necessary to obtain good frequency stability. The paper describes a new device based on an operational transconductance ampli fier (OTA) with a very high bandwidth. Experimental results illustrate the ability of the sensor system to detect small amounts of special a nalytes in liquids.