¡@¡@An integrated device, which can be used to detect the ferrous particle concentration and the viscosity of the lubricating oils, is designed and manufactured. These two measurement units are conducted through the theoretical analysis of the design model, and the design drawing, the manufacturing, and the assembly of the components, respectively. Finally, the experiments are conducted to detect the performance of this integrated device. ¡@¡@In the measurement unit of the ferrous particle concentration, the geometry for the poles of the magnet and the air-gap flux density are designed using the Ohm¡¦s law and the magnetic hysteresis law, so that the ferrous particles in the lubricating oils is captured by the magnetic attraction at the air gap between the poles of the magnet. The pile of ferrous particles is connected with the Hall-effect sensors into a magnetic circuit. Results show that the sensitivity of the ferrous concentration measured using the magnetic circuit in series is about 600 times that using the magnetic circuit in parallel. The error is less than 0.3 ppm under the eight repeat tests. ¡@¡@In the measurement unit of the viscosity of the lubricating oils, the piston is squeezed into the oil to measure the viscosity. Since the container is easy to clean, the precision and the repeatability can be promoted. The error is less than 5% under the eight repeat tests. ¡@¡@When these two units are integrated into a measuring device, it is found that the interference between them can be neglected, and only one analysis procedure of sample oil can measure the ferrous particle concentration and the viscosity of the lubricating oils. Hence, the user can detect the lubricating oils used in many machines using this device to understand the abnormal wear and the deterioration of the oil.