Electrification time

The IPC Multi-Purpose Test Pattern, IPC-B-25 is shown in Figure 1. Test boards were fabricated in-house containing the IPC-B-25 pattern on both sides. The center comb pattern with 12.5 mil copper conductors and 12.5 mil spaces was used to measure the insulation resistance. A total of eight values were measured for each board and the average reported. A General Radio Model 1864 Megohmmeter was used to measure the insulation resistance using 100 volts DC and a 60 second electrification time. 

The Ki value of a PVC cable compound as a function of the electrification time... 

The measurements, at nine discrete temperatures, were performed with an electrification voltage of 500 Volt and an electrification time of thirty minutes. The measured currents were used to calculate the so-called p-60 value and the p-dc value, see 5.1.5. 

All measurements were performed with an electrification voltage of 1000 Volt and an electrification time of twenty minutes. This electrification time proved to be sufficient to avoid contributions of time dependent charging currents (see Chapter 5.1). The in this way performed measurements agree with the recommendations given in ASTM D257 and IEC 93 methods. 

Test potential is applied via the "charging" position of the instrument switch for at least about 10% of the specified electrification time (usually about 5 seconds). 

The instrument connection switch is moved to the "read" position and the range switch. set to an appropriate level at least 10 seconds before reading the resistance at the specified electrification time. The indicated resistance will not usually be constant but will steadily increase, at a rate dependent on the test material. 

The RpC product decreases (nearly exponentially for many dielectrics) when the temperature increases (Fig. 2.52). It is approximately halved (RIFA, 1990/91) for each 7°C of temperature rise the temperature where this decrease starts is different for different dielectrics. The RpC product also can vary with electrification time (due to dielectric absorption effects) and can increase (up to two orders of magnitude) in... 

Resistivity is sensitive to temperature and humidity, and tests are usually made after conditioning in the standard atmosphere of 23 2°C and 50 5%RH. Surface resistivity is particularly sensitive to humidity and the standard humidity should be maintained during the test. Where results are to be used as design or performance data, it would be advisable to test over a range of humidities and (perhaps) temperatures. The resistance of the test piece is measured after the test voltage has been applied for a set period, usually 1 min, although this will very often not be an adequate time for the current, and hence the measured resistivity, to reach an equilibrium value. If it is suspected that this is the case, resistivity can be monitored as a function of time of electrification. 

The discussion given in BS 4618, Sections 2.3 and 2.48 on design data for plastics applies in principle to rubbers, and stresses the advantage of measuring resistivity as a function of temperature, humidity, electric stress and time of electrification. 

Electric strength is usually taken as the nominal voltage gradient (applied voltage divided by test piece thickness) at which breakdown occurs under specified conditions of test. These specified conditions of test are important as the measured electric strength is not an intrinsic property of the material but depends on test piece thickness, time of electrification and the electrode geometry, as well as on conditioning of the material. 

Since Coulomb forces decay much more slowly than van der Waals forces, an EFM experiment can be performed even without any feedback, if the sample roughness is low compared to the tip-sample distance. Terris et al. used this technique for the first time to investigate a contact electrification of a metal-insulator system [355-357]. Later, further improved experiments on contact electrification with single charge sensitivity were performed by... 

This industry is on the decline due to the peace-time agreements and Comprehensive Test Ban Treaty, (CTBT). Under this agreement, enrichment of UF6 is restricted to lower grade U235 for reactor fuel to be used in commercial electric power generation. In North America, there is an antinuclear atmosphere, hence it is less likely to see the expansion or additions of nuclear power plants in the USA. Whereas China, India, and East European countries may require additional nuclear fuel for their fast growing industries and electrification of the rural areas. 

The SA node lies in the right atrium, in an epicardial location and functions as the primary source of the electrical impulse formation. It consists of specialized muscle cells, smaller than ventricular cells containing few contractile elements. Due to its location, the action potential generated traverses the atria first, causing the primary contraction. The action potential is relayed to the AV node, the conduit for the electrification of the ventricles. The signal must pass through the AV node, otherwise the atria and the ventricles are electrically insulated from each other. A time delay in transmission is needed for the atria to be emptied of blood. 

Completing a circuit and measuring the current that flows on contact or separation can quantify the transfer of electrons [2]. A typical result on contact electrification is shown in Figure 24.3. The time constants associated with the current peaks can be adjusted by inserting a series resistance in the measurement circuit. In real time, the equilibration of surface state electrons occurs instantaneously. In these experiments, the plasma polymer of tetrafluoroethylene (TFE) was deposited on two different substrate, nylon film and polished brass, and the contact and separation currents were measured with a (uncoated) brass probe... 

The observation of PCBs at almost all sampling points poses a challenge as to the source of the compounds. These tre rural areas with very little electrification points. At this time it is speculative to attribute the source to any one activity except to say that there may be unauthorized dumping of PCBs in the catchments. Further studies are needed to pinpoint the point somce of PCBs in the Lake Victoria waters and sediments. However, at present the data indicate that river mouths have higher concentrations of PCBs except for a few bays that are unique, that is Hippo Point, Son and Port Victoria which are known for active eommercial activities. 

The time of electrification, unless otherwise specified, should be 60 s and the applied direct voltage = 500 5 V. 

Volume Resistivity or Conductivity Measure the dimensions of the electrodes and width of the guard gap, g, accurately. Unless otherwise specified, the time of electrification should be 60 s, and the applied direct voltage... 

Surface Resistivity or Conductivity The electrode dimensions and the distance between the electrodes, g, are to be measured accurately. The surface resistance or conductance between electrodes No. 1 and 2 is measured with a suitable device [Brown, 1981]. The time of electrification should be 60 s and the applied direct voltage shall be 500 5 V. 

If the particle is an electron, then ipif/ is proportional to the average electric density at x, y, z. if/if/, being independent of time, can be represented in space as a continuous cloud of electrification varying from point to point in a manner shown by the solution of the wave equation which has yielded if/. Although this cloud is fictitious and corresponds to a probability or to a time-average, it is very convenient to visualize its spatial symmetry, and even to look upon the electrical distribution as a real one. This in one sense illustrates the reluctance with which naive realism is forsaken. 

Most antistatic additives are polar waxes the alkane chain part of the molecule is attracted to the polymer, while the hydrophilic end attracts water. This moisture forms a thin conductive film on the surface of the plastic. A charge decay half time of 0.1 s or less provides adequate protection against static electrification. To achieve this, the surface resistivity must be less than 3 x 10 fl/square. Although surface films are worn away by abrasion, they are replenished by the additive slowly diffusing to the polymer surface. They will not function adequately when the relative humidity is less than 15% (not a problem in the UK ), and cannot be used for specialised polymers with melt processing temperatures exceeding 300 °C. The use of conducting fillers (see the next section) is a more permanent solution to static electrification. 

A void or bubble occurring in the center of a heavy thermoplastic part, usually caused by excessive shrinkage. The electrical resistance between opposite faces of a 1 cm cube of insulating material. It is measured under prescribed conditions using a direct current potential after a specified time of electrification. Also called specific insulation resistance (ASTM D257). 

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