. Rare and Ancient Equipment 1070495 V1 HPM equipment description DS22bit free download

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CERN Project ID LHC Doc. Creator Miguel Cerqueira Bastos CH-1211 Geneva 23 Sub-Proj. ID - EDMS Doc. 1070495 Switzerland Equip. Code - Doc Rev. / Rev. Date 1.0 / 2009-01-25 TE-EPC Power Converter Group Equipment Description The LHC DS22 bit ADC The LHC high precision current measurement chain The main power converters in LHC require an unprecedented level of accuracy in the control of current to the superconducting magnets, in the order of ~10-6. The power converter output current accuracy is mainly determined by the DCCT (Direct Current Current Transducer) and ADC (Analogue-Digital Converter) employed. There are three types of ADCs used in the LHC: a 16 bit Delta Sigma and a 16 bit SAR, both included in the power converters' digital controller electronics (FGC) and, in the case of the main and inner triplet power converters, a 22 bit delta sigma standalone unit. Introduction to Delta sigma converters The ADC employed in the digital regulation loops for the LHC requires high resolution and accurate digitization of low frequency waveforms. Since the ADC can be one of the major sources of error in the magnet current, along with the current transducer, its performance largely determines the overall accuracy which can be obtained. The potential of the Delta-Sigma method to deliver ppm performance determined the choice of this method for the LHC. The simplified block diagram of a first order Delta sigma ADC is shown in Fig.1. Fig. 1