FR016: Constructing a pyroelectric/piezoelectric sensor using a PNZT capacitor

Radiant introduced its EDU educational tester a year-and-a-half ago with the goal of providing engineering and science students a tool for self-paced learning about ferroelectric materials and their applications. Radiant has recently created a matching sensor circuit and sensor chip pair to supplement the EDU as a learning tool. The chip contains a 1-micron thick, 16 square millimeter PNZT capacitor with passivation and bond pads. The geometry of the sensor chip allows it to be used without packaging so that it may be handled with tweezers and soldered directly to a PC board with the proper footprint. The capacitor is large enough that direct force can easily be applied to the capacitor surface by human touch. The sensor circuit uses an integrating charge amplifier with no bias voltage to detect changes in the capacitor polarization, making it sensitive to the smallest environmental stimulus. It cannot distinguish, however, between temperature changes and the application of force to the capacitor surface. Nonetheless, the sensor can detect temperature changes in the hundredths of degrees Celsius and see the pressure pulse wave generated by a human heartbeat.