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A semiconductor capacitance -type accelerometer utilizing a pulse width modulation (PWM) electrostatic servo technique has been developed. Highly accurate detection of very small and low frequency acceleration became possible with the PWM sensing method. The limited air gaps between the movable and fixed electrodes ensured compatibility between high sensitivity and durability, while transverse sensitivity and temperature coefficient were reduced due to the symmetric structure of the sensing device. This sensor has been designed for the measurement range of 0 to ±1g, ±2g and 0 to 50Hz. The accelerometer is composed of two chips: the sensing device made by silicon micromachining technology and the custom IC made by bipolar CMOS technology. In this paper, we present the fundamental sensing principle, the sensing device, the custom IC and the characteristics of the new accelerometer.

The oxygen ion conductive solid electrolyte cell served as a device for measuring the combustibles content and the oxygen content of an exhaust gas. The cell is comprised of a tubular electrolyte, two opposed electrodes and a porous diffusion layer located on the outer electrode surface. The sensor is employed to measure both rich and lean air fuel ratio through the use of an electronic circuit pumping the oxygen ions to achieve a constant voltage between the electrodes. The wide range detecting capability makes it particularly attractive for air fuel ratio control applications associated with the internal combustion engine. The result of the performance tests are as follows, Detecting range (air excess ratio λ) : 0.8 - “∞ Step response time constant (63%) : 200ms Warm up time. - less than 80 sec at 20°C We found in the durability test concerned with the heat cycle and contamination that if initial aging treatment is applied the output variation ratio (. λ/λ) is limited with in : 5%.