The History of Electric Measuring Instruments and Active Components Society of Historical Metrology , Japan
Precision electric meters are indispensable to the development of technology in this age. The first electric measuring instruments, however, were physically impossible to transport, and were functionally inadequate for use in a laboratory. The measuring instruments of today have evolved into sturdy, easy-to-use instruments with higher performance, adopting new active components which have appeared one after another. Expanding in functionality, measuring instruments that have adopted such new technology have enabled even more precise measurement. The users have also expanded from research organizations and educational facilities, to the manufacturers of electrical equipment and electronic parts. The measuring instrument manufacturers were able to supply more convenient measuring instruments to the user, and conversely, the user, the manufacturers of electrical equipment and electronic parts, needed more easy-to-use and highly precise measuring instruments in order to respond to a rapidly increasing demand. Consequently, cheap and high quality electronic parts were supplied to the market, and the measuring instrument manufacturers were also able to develop new measuring instruments using those parts. In fact, it can be said that they have been mutually complementary. It should not be forgotten that the demand for electronic components for consumer use has also driven the whole in the meantime.
Stabilized feed-back amplifiers
This paper describes and explains the theory of the feed-back principle and demonstrates how stability of amplification, reduction of modulation products, and certain other advantages follow when stabilized feed-back is applied to an amplifier. The underlying principle of design by means of which “singing” is avoided also is set forth. The paper concludes with some examples of results obtained on amplifiers which have been built employing this new principle.
Formation of unexpected ions from a first-generation polyamidoamine dendrimer by use of methanol: an artefact due to electrospray emitter corrosion?
We report the formation of unexpected ions during the analyses of a first-generation polyamidoamine dendrimer in negative ion mode using an ion trap equipped with an electrospray ionisation source. These surprising ions corresponded to an increase of 12 m/z units over those expected. The formation of the unexpected ions was dependent on the tuning of the solution flow rate and the capillary high voltage. In addition, measurements of unusual value of the current suggested that a reaction was occurring in the corona plasma. The influence of methanol in this phenomenon was demonstrated by using CD(3)OH in the sample preparation. We propose two structures to explain the observed adduct based on the results of MS(2) experiments and by referring to previous work dealing with 12 m/z units addition. We showed that a corona discharge caused by alterations taking place to the electrospray capillary emitter was the origin of these unexpected ions. Finally, we discuss the mechanism involved in the formation of the ions and we propose means to control such artefacts.