Earth referenced

The principle, as illustrated in Fig. 3.1, is that anybody simultaneously touching one pole of the unreferenced supply and earth will not experience an electric shock because there is no complete circuit back to the point of supply. However, if there were to be an insulation failure that inadvertently connected one pole to earth, the system would become an earth referenced supply and anybody touching the live pole and earth would be at risk, as illustrated in Fig. 3.1. For that reason, it is very important that unreferenced systems are routinely tested for such insulation failures. Note that Fig. 3.1... 

Earthed equipotential bonding and automatic disconnection of supply, known as EEBADS, is the most common technique employed for protection against indirect contact electric shock. Essentially, for earth-referenced supplies, the technique requires the exposed conductive parts of Class I apparatus and equipment to be earthed by means of the protective conductor, with the protective conductor connected back to the main earthing terminal of the installation. 

Welding sets with earth-referenced secondary windings at the transformer should be regarded as obsolete and taken out of use to prevent the stray currents causing damage. 

As it does with all objects on the surface of the Earth, gravity exerts its effects on the molecules of the atmosphere. The weight generated by these molecules is referred to as atmospheric, or barometric, pressure (Patm). At sea level, atmospheric pressure is 760 mmHg. In order to simplify this discussion, atmospheric pressure will be normalized to 0 mmHg (or 0 cmH20) and all other pressures are referenced to this. 

The preparations of rare-earth trihalides can be found in various books (2-8) and in Taylor s review (2 ). This review, however, did not include the preparation of scandium and yttrium trihalides, and only covered the preparation of the trifluorides very briefly. We have reviewed the preparation of all the trihalides (including scandium and yttrium) from Taylor s review up to June 1979 and have also included some methods and references missed by Taylor. Although we have mentioned all the methods available for the preparation of the trihalides, emphasis has been placed on the methods used since Taylor s review, and these have been referenced fully, whereas for the other methods, Taylor s review is recommended as a source of references. 

Virtually all of the published Mg isotope data obtained by MC-ICPMS are referenced to the SRM 980 standard at the time of this writing. Fortunately, the vast majority were obtained using as the standard a single batch of dissolved SRM 980 housed in the Department of Earth Sciences, University of Oxford. This standard has been referred to as SRM 980 O (Galy et al. 2003). However, SRM 980 0 was never intended to serve as a primary standard and there is the need to establish an alternative primary standard of uniform composition. 

The atmosphere is made up of a number of gases and, near the earth s surface, water vapor as well. The pressure exerted by atmospheric air is referenced to sea level. Average atmospheric pressure is 1013 mbar (equivalent to the atmosphere , a unit of measure used earlier). Table VIII in Chapter 9 shows the composition of the standard atmosphere at relative humidity of 50 % and temperature of 20 °C. In terms of vacuum technology the following points should be noted in regard to the composition of the air ... 

Fig. 4.2, as shown, with the ground referenced to the output (make sure the power supply in not tied to earth ground). 

DAY (d). A unit of time, the exact definition of which is dependent upon which system of time measurement Is referred to, i.e., apparent solar time, mean solar time, universal time, apparent sidereal time, ephemera time, or atomic time. See Time. With exception of atomic time, the time base is referenced to rotation of the Earth. For general purposes, a day is considered tire period taken for 1 revolution of the Earth about its axis... 

Kilo bar—unit of measure used to express the high pressures found within Earth s interior. It is referenced to air pressure, the force exerted by the weight of the atmosphere at Earth s surface, which equals one bar. A kilobar is 1000 bars. 

Metal ions separation for hydrometallurgical applications has attracted considerable interest. Selective separations of alkali, alkali earth, heavy metal ions, rare earth, precious metals, etc. are studied by many authors using all the above-described techniques. Referenced works in metal separations classified according to the OHLM techniques with types of membrane walls and carriers used are listed in Table 13.6. 

Fig. 2. The rare-earth elements now used in rare earth-cobalt permanent magnets, their effect on magnet properties (referenced to Sm alloy), and relative cost of the rare earth component.

U nless otherwise noted, rare-earth entries from Martin et al. (1974) or Morss (1985) and references therein actinide entries (U -Cf) from Schoebrechts et al. (1989) and referenced therein other actinides from Morss (1986) and references therein. 

Since only a few standard aqueous electrode potentials °(Ln /Ln ) have been determined electrochemically, others have been estimated [e.g., (Dy /Dy ) (Morss and Fahey 1976, Morss and Spence 1992)] from calorimetric measurements on their dichlorides or from spectroscopic correlations. The only experimental values of °(An /An " ) are from radioelectrochemical measurements on Fm-No (David 1986a) and coprecipitation studies (Mikheev 1988,1992). Spectroscopic correlations of (An /An ) have also been made (section 3.4). These reduction potentials have been assessed for the rare earths (Morss 1985), for the lighter actinides (Martinot and Fuger 1985), and for the heavier actinides (David 1986a, Morss 1986). With the exception of uranium, neptunium and plutonium species [(Fuger 1992, table 1), discussed in section 2.4.1] and No + (discussed in section 2.4.1), these potentials are still valid. We note that the (An /An) values depend on the S°[An (aq)] which are referenced to a value for Pu (aq) that is based in part on experiment but also required estimation of S°[PuClj 6H20(s)]. 

In the electrical separation technique, the supply is not earthed or otherwise referenced - such systems are commonly known as isolated or unreferenced supplies. The source for this type of system is usually a safety isolating transformer or its equivalent and the circuit voltage is limited to a maximum of 500 V. 

This Regulation aims to prevent open circuits or high impedances arising in the referenced conductors, which could cause hazardous potential differences between them and the reference point, and to prevent the flow of fault current in systems employing automatic disconnection protection techniques. In most cases, earth is the referencing point for supply systems but there are exceptions, such as motor vehicle wiring systems which are not earthed and which use the chassis as both a reference point and a common return. Other non-earthed systems connect the protective conductor to one of the supply poles. 

Further analytical work by SSMS on the sample is considered if certain rare earth impurities require lower error limits. Internal referencing is employed in which the reference is an appropriately selected rare earth. The rare earth levels, determined with internal referencing, are then compared to the determinations for these same elements in the original sample. The ratios of these determinations should be constant and this constant can be used as a correction factor for all of the determinations in the original sample. The Laboratory is presently changing the internal standardization step to incorporate the use of isotope dilution when it is practical. 

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