Frequency Resolved Partial Discharges Based on Spectral Pulse Counting

A partial discharge (PD) classification methodology based counting PD pulses in the spectral domain is proposed and presented in this paper. The spectral counting data are processed using the proposed PD Spectral Pulse Counting Mapping technique (PD-SPCM), which leads to a Frequency-Resolved Partial Discharges (FRPD) map. The proposed map is then used for PD detection and classification. In this work, corona and slot FRPDs are presented in frequency bands up to 500 MHz, obtained from laboratory measurements performed using two hydro-generator stator bars. The electromagnetic signals from the PDs were captured using a patch antenna designed for this purpose and a spectral analyzer. The corona and slot PDs were chosen because one can be mistakenly classified as the other because they may present similar Phase Resolved PD (PRPD) maps and may occupy shared spectral bands. Furthermore, corona and slot PDs can occur concurrently. The obtained results show that the corona and slot PDs can be properly identified using the developed methodology, even when they occur simultaneously. This is possible because, as it is experimentally demonstrated, corona and slot PDs have appreciable levels of spectral pulse counting in particular bands of the frequency spectrum.

An Optimized Pulse-Counting Method for Compensation Vector Calculation in the Automatic Balancer

The accuracy of the counterweight positions in an automatic balancing system deeply affects dynamic balancing. Compensation vector is synthesized by the two counterweights located in the electromagnetic dual-weight automatic balancer. Therefore, if the position of the counterweight is inaccurate, it may result in a wrong adjustment and a larger imbalance of the rotor system. In this paper, an optimized pulse counting method for compensation vector calculation in an electromagnetic dual-weight balancing system is proposed based on a programmable logic controller (PLC). A propeller automatic balancing simulation test bench is used to verify the effect of the method by obtaining the positions of the counterweights and synthesizing the compensation vector in the working mode. The error is less than 1/80 which means that it does not exceed one step in the 80-position-balancer at 1200 rpm. The proposed control system can work without computers or high-speed data acquisition equipment, which improves the stability and flexibility of the control system, facilitates the design of the automatic balancing system, and shows excellent potential for industrial applications.

Innovative Detection Strategies on Large Geometry SIMS open new challenging applications for light isotope ratio analyses

<p>Large Geometry Secondary Ion Mass Spectrometry (LG-SIMS), operating in multicollection mode, allows high precision light isotope ratio measurements at high lateral resolution (tens of μm down to sub-μm range). For some challenging applications involving fine scale analysis of low abundance isotopes (i.e. <sup>17</sup>O or <sup>36</sup>S) or low-concentration elements (i.e. nitrogen in diamonds) measurement of low signal intensities is required. Traditionally, count rates between the upper level of pulse counting systems ~10<sup>5</sup> c/s and the lower level of Faraday Cup (FC) measurements ~10<sup>6</sup> c/s are considered to be in a “gap area” where neither detection protocol can achieve performance better than the 1‰ level.</p><p>Faraday Cup detectors (FC) offer high precision with no need for gain monitoring, however the uncertainty of FC measurements depends on the signal to noise ratio. One approach for measuring low signal intensities is to use FCs coupled to electrometers with high ohmic resistors. CAMECA LG-SIMS can now be equipped with low noise 10<sup>12</sup> Ω resistor FC preamplifier boards for measuring signal intensities down to the ~ 3 x 10<sup>5</sup> c/s range with precision better than the 0.5‰ level (1SD).</p><p>For measurement of low-abundance isotopes, a complementary approach consists of using discrete-dynode pulse counting electron multiplier (EM) detectors, for which drift and aging effects are minimized using a fast automated EM high voltage adjustment routine.</p><p>During this PICO presentation, we will discuss the relevance of the detector choice (FC 10<sup>12</sup> Ω vs EM) for few examples of innovative applications.</p><p>Example of mass independent fractionation:</p><p>In addition to classical isotopic ratio measurements (e.g. δ<sup>13</sup>C, δ<sup>15</sup>N, δ<sup>18</sup>O or δ<sup>34</sup>S), for which the instrumental mass fractionation (IMF) correction is mostly limited by the natural heterogeneity (chemical and isotopic) of the reference material, SIMS is particularly well suited for the measurement of mass independent fractionation (MIF, e.g. ∆<sup>33</sup>S, ∆<sup>36</sup>S and ∆<sup>17</sup>O). Along with classical geochemical processes, the degree of isotopic fractionation scales with the difference in mass of the isotopes involved (i.e. δ<sup>33</sup>S ≈ 0.515 * δ<sup>34</sup>S). MIF refers to non-conventional ratios that depart from these mass dependent rules. As instrumental mass fractionation has been shown to be strictly mass dependent, MIF measurements are not subject to IMF correction and are therefore measured directly. The use of SIMS in this specific case is particularly well suited and allows to fully explore the rich phenomenology of MIF source processes. We will discuss the advantages and disadvantages of using FC 10<sup>12</sup> Ω for the minor Sulphur isotope (<sup>36</sup>S) measurement.</p><p>Carbon and Nitrogen in diamond:</p><p>We will also show a recent analytical development aiming to measure δ<sup>13</sup>C in diamonds at mass resolution of ~5000 (allowing the full separation of <sup>13</sup>C- and <sup>12</sup>CH-) as well as N-content and N-isotopes in diamonds at a mass resolution of ~9000 (full separation of <sup>12</sup>C<sup>14</sup>N- and <sup>13</sup>C<sup>13</sup>C-).  For this purpose, the use of FC 10<sup>12</sup> Ω greatly improves the data quality and allows the simultaneous measurement of N-content and δ<sup>15</sup>N.</p>

Single particle inductively coupled plasma mass spectrometry: investigating nonlinear response observed in pulse counting mode and extending the linear dynamic range by compensating for dead time related count losses on a microsecond timescale

Sampling of the pulse-counting signal with μs time-resolution provided a functional compensation for dead-time related count losses in spICP-MS, ultimately improving the linear dynamic range by one order of magnitude towards higher count rates.