Summarising, piezoresistive accelerometers can have a high dynamic range, in combination with a sufficiently high resonance frequency for modal analysis applications. The resolution that can be obtained in practice is expected to be sufficient, when using a low noise measurement amplifier, that can handle the DC response of the accelerometer. A drawback of piezoresistive detection is the temperature sensitivity, although effective temperature compensation schemes have been developed.

View full abstract

A capacitive type 3-axis accelerometer for general industrial use was developed by using micro machining technology. A stable structure over the temperature was found by FEM analyses and experiments. The mechanism of non-linearity and cross-axis interference caused by the structure and electronics circuit were explained. And compensation methods were shown. The capacitive type 3-axis accelerometer was assembled with its control circuit and evaluated the performance. Typical performance is as follows. Acceleration range is ±2g, operating temperature range is from -30°C to 75°C, sensitivity is 1V/g, cross-axis sensitivity is less than 1% and offset variation over the temperature is less than 2mg/°C.

View full abstract

A thermistor bolometer (an infrared radiation sensor) for a clinical tympanic thermometer has been newly developed and quantitatively evaluated. In order to mount the sensor on a tip of a flexible probe and to insert it into human's auricle, the sensor iscompleted in a very small size (2.2mm×2.3mm×0.8mm) using silicon micromachining technologies. Further the sensor can selectively detect the infrared radiation only from a tympanic membrane.
The sensor has been designed especially concerning the reduction of heat loss. To realize high sensitivity, a pair of infrared sensing regions of the sensor is made inthe shape of micro-air-bridge. It is encapsulated in a vacuum micro-chamber conformed between silicon substrates. The effectiveness of vacuum encapsulation is clearly proved by experiment.
The sensor shows the sufficient performance for the tympanic thermometer with the sensitivity of 5000V/W and the noise equivalent temperature difference (NETD) of 0.062°C at a D.C. bias voltage of 1.56V.

View full abstract

A vibrating microgyroscope with a thin polysilicon resonator was fabricated using silicon surface micromachining, and its basic properties were investigated. The 400×800μm² resonator is driven in a lateral direction by electrostatic force, and angular rate is detected as capacitance change between the resonator and its substrate. Mechanical Q factors for the driving and detecting modes of the polysilicon resonator are 2, 800 and 16, 000, respectively, at pressures below 0.1Pa. The test device worked in a vacuum, and output intensity was decreased at high ambient pressures. A noise-equivalent rate of 2deg/s was obtained at 1Pa.

View full abstract

A new ultrasonic three-dimensional imaging method is described for inspection. We developed a new two-dimensional ultrasonic scanning method using a circular-array transducer in which numbers of small piezoelectric elements were arranged in a circle. By computer simulation, it was proved that circular-array had lower grating-lobe level and made more uniform scanning in space than a matrix-array. To obtain 3-D data, we proposed two-dimensional electronic scanning method which was made the best use of the geometric characteristic of a circular array transducer. The results of experiments for generation of an ultrasonic beam and 2-D imaging using a trial transducer confirmed directivity of the transducer and possibility of 3-D imaging by the circular array transducer. Obtained data in a ultrasonic testing is 4-dimensions, this is echo position(x, y, z) and sound intensity. To express the data, we proposed a new color conversion technique. Hue and brightness were used as a parameter of perspective and sound intensity, respectively. We evaluated the method with the off-line system to develop the real-time 3-D imaging system.

View full abstract

A microfabricated tunneling unit (LTU: lateral tunneling unit) was successfully applied to minute displacement detection. An LTU has a tunneling tip protruding from the chip edge and can be moved back and forth by a microactuator. The tip end was positioned close to a planar electrode attached to a PZT actuator. When the PZT actuator moved, the gap between the tip and the opposing electrode was kept constant by moving the tip so that the tunneling current flows through the gap should be constant. The displacement of the planar electrode was determined from the change in the microactuator's driving voltage.

View full abstract

The diaphragm release technique presented here contributes to improve the processing yield of suspended microstructures. We believe that it extends the range of micromachining application because it is used to structural materials other than polysilicon, and because it is compatible with existing bulk micromachining processes.

View full abstract