Fluke dev in high bw p amp tech free download

File name dev_in_high_bw_p_amp_tech.pdf

Developments in high bandwidth power amplifier technology for compact cost effective calibrator applications. Paul C. A. Roberts - Applied Technology Manager, Fluke Precision Measurement Limited, UK. Abstract: The workload of a modern calibration laboratory has placed ever greater demands on the Calibration Source, both in terms of functionality and the combination of voltage, current and frequency required to calibrate today's diverse range of instruments. This need for high voltage and high current at high frequency into demanding loads such as clamp meters and current coils, combined with a desire to produce ever more economic and compact calibrators, has resulted in a number of significant developments in the transition from the vacuum tube designs common in the past to today's solid state designs employing the latest semiconductor and transformer technologies. This paper explores the development of technologies enabling the design of high bandwidth power amplifiers compact enough to be integrated within the calibrator in a single enclosure, eliminating the need for a separate Boost Amplifier, and their impact on calibration applications. Introduction: During the 1970s a number of alternating voltage calibrators were successfully developed and deployed, but where a high voltage output was required a separate power or boost amplifier was always involved. These designs were based on vacuum tubes, often utilizing tubes designed as UHF radio transmitters because of their availability in suitable power ratings and their physical suitability for mechanical mounting. Reliability was poor and many manufacturers products earned a well deserved reputation for fragility - and with one exception those manufacturers either collapsed or chose to leave the calibration business. The most successful AC voltage calibrator/amplifier partnership continued into the 1980s and was the competitive target for a new generation of AC voltage calibrator released in 1984 - the Datron 4200. This new design employed fully solid state technology with an integrated power amplifier capable of delivering 1000V at frequencies up to 30kHz extending to 100kHz at 750V. The size of this unit was identical to its closest competitor which could only provide 200V - the additional vacuum tube boost amplifier required to obtain 1000V capability occupied almost twice the volume of its partner. Analysis of workloads revealed that high voltage capability at high frequency was an essential requirement for complete calibration of the precision DMMs appearing on the market at that time - one in particular which required 700V at 100kHz. And this even in the days before ISO9000 was driving the need for complete calibrations!. However, output current requirements were within the capabilities of semiconductors - vacuum tube designs were overkill for the actual workload in this respect. The technology which enabled such a compact p