Humidity sensors are fabricated on ceramic substrates with Ag–Pd interdigitated electrodes by loading ZnO nanorods as a sensing material. X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM) are applied to characterize these ZnO nanorods. An auto test system is developed by connecting a ZL-5 model LCR analyzer and a PCI–GPIB interface. Several programs are designed using the LabVIEW environment to measure the humidity sensing properties of our sensors, such as response–recovery curves, capacitance characteristics, frequency properties, and complex impedance properties. The results make our system a good candidate in sensor investigations.