Development Based on Study of Piezoelectric Elements from Before WWIIRion’s history can be traced back to the Kobayasi Institute of Physical Research, which was founded in 1940. Since its inception, piezoelectric ceramics and other piezoelectric elements have con-stituted one of the elds of research at the institute.“Rion is currently renowned for its hearing aids, sound level meters, and particle counters. But my understanding is that we started off with the study of piezoelectricity,” says Kazuhiro Shi-momura who’s been involved in the development for many years. To com-mercialize the results of the institute’s research, Kobayasi-riken Co., Ltd. was founded, which later became Rion Co., Ltd. During this time, acceleration sen-sors based on piezoelectric ceramics (“ceramics” hereafter) were developed. This was from the late 1960s to the early 1970s, when noise and vibration pollution problems were beginning to be recognized as a social problem, and vibration pickups based on acceleration sensors were rst introduced to mea-sure pollution effects. This was followed by a rush for the development of gener-al purpose pickups.By that time, Rion already had a wealth of knowledge and expertise on piezoelectric elements, which meant it was able to present a lineup of general purpose pickups from the late 1970s to the early 1980s. The older models were reorganized while newer models were being developed, and this continuing process resulted in our present lineup.The Reference Pickup—Proof of the Pinnacle of TechnologyThe next product developed was the reference accelerometer. A reference accelerometer is used to calibrate the sensitivity and frequency characteristics of general purpose accelerometers and to check whether their performance is maintained. In other words, it is a mis-sion-critical product for manufacturers of measuring instruments. This is the most precise of all accelerometers and the instrument used by other manu-facturers of measuring instruments to check the precision of their products.Stability is the most important fea-ture required of calibration instruments. The measured properties must be certi-ed by ofcial bodies. The technological hurdles required to be overcome in the production process to ensure precision at levels far exceeding those of normal accelerometers are enormous.“We used the layered Bi (bismuth) oxide developed by the piezoelectric laboratory at the Kobayasi Institute of Physical Research to ensure extremely high precision and operational stabil-ity,” says Shimomura, looking back on the development history. “The mate-rials used in reference accelerometers abroad are mainly single crystals like quartz. To the best of my knowledge, no other manufacturers used ceramics. Needless to say, our accelerometer was the rst reference accelerometer to be made in Japan.”A change in the blending ratio of ceramic materials of as little as 1% can completely alter a product’s characteris-tics. One reason Rion was so successful in this most demanding development was a group of outstanding research-ers in the piezoelectric laboratory at the Kobayasi Institute of Physical Research. The ceramics used in the current refer-ence accelerometer model have barely changed since the early days of devel-opment. In other words, it could be said that the reference accelerometer is a product that is reaching the stage of ultimate perfection.Accelerometer for High Tem-perature Nuclear Power Facili-ties, to Withstand Operation in Extreme EnvironmentsThe next model developed was a accel-erometer with high temperature resis-tance. When pickups are installed for vi-bration measurements at power plants and manufacturing plants, they’re often placed in high temperature environ-ments. From the rst half of the 1980s, Rion began developing accelerometers for use at high temperatures.Initially, the characteristics of the ceramics used for general purpose ac-celerometers were improved to develop products with enhanced temperature characteristics—specically, the PV-44A and PV-65, which can be used in tem-perature environments of up to 260°C.Work then progressed to the devel-8[PV-03]The PV03 is a reference piezoelectric accelerometer for secondary calibration (backtoback comparative calibration) of various piezoelectric accelerometers. The absolute calibration for the PV03 is performed in accordance with ISO 53471 “Primary vibration calibration by laser interferometry,” meaning JCSS calibration certificates can be issued after calibration using the PV03.[PV-63]The PV63 is a sheartype accelerometer with high temperature resistance to measure machine vibrations, designed specically for nuclear power facilities. Featuring a stainless steel casing, it’s rated for use at temperatures from −20°C to 300°C.
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