Off-line applications

A period of time over which the input line voltage completely disappears (the specification is typically 8mS for 60Hz ac off-line applications). 

In ae off-line applications the common-mode choke is typically used and its design procedure can be found in Appendix E. The Alters resemble pi Alters, but are actually bi-directional L-C Alters. The important function is to Alter the noise generated by the switcher before it exits via the input power lines. 

A PWM switching power supply that is designed with no extraordinary loss-control methods will exliibit efficiencies as seen in Table 3-3. For switching power supplies that have no problem in getting rid of the heat, such as some off-line applications, the aforementioned efficiencies may be satisfactory. For portable applications and equipment that must be small in size much better efficiencies must be sought. To improve the overall efficiency of a power supply, several techniques can be used. 

Of the analytical techniques available for process analytical measmements, IR is one of the most versatile, where all physical forms of a sample may be considered - gases, liquids, solids and even mixed phase materials. A wide range of sample interfaces (sampling accessories) have been developed for infrared spectroscopy over the past 20 to 30 years and many of these can be adapted for either near-lme/at-lme production control or on-line process monitoring applications. For continuous on-line measurements applications may be limited to liquids and gases. However, for applications that have human interaction, such as near-line measurements, then all material types can be considered. For continuous measurements sample condition, as it exists within the process, may be an issue and factors such as temperature, pressure, chemical interfer-ants (such as solvents), and particulate matter may need to be addressed. In off-line applications this may be addressed by the way that the sample is handled, but for continuous on-line process applications this has to be accommodated by a sampling system. 

In general two types of secondary coatings are used in conjunction with the primary coatings described above. UV-curable epoxy acrylates or urethane acrylates are commonly used for in-line application, as the fiber is drawn. These same materials are also used extensively as single coatings. Extruded thermoplastics, such as nylon or polyester elastomers, are frequently used for off-line application processes. 

Eor all these applications, special attention should be given to the interfaces between dynamical and chemical processes. While it is recognised that an on-line coupling of these processes will be ultimately necessary, there is still a series of processes that need special attention also under off-line applications, as named below. 

Fig. 15.4. Reversed phase and normal phase mode of operation in the off-line application of MIPS in SPE.

Fig. 2 Off-line application of MIP-SPE. Representation of the two modes of operation normal phase (selective binding) and reversed phase (nonselective binding-selective desorption).

If a particular technique, that is, mass spectrometry is listed in this column, it implies online coupling. Off-line application of mass spectrometry is listed in the column as other methods. 

In effect, what we are therefore always implicitly doing in off-line applications is... 

Therefore in general, in high-voltage dc-dc (or off-line) applications, the MIN of the current limit may sometimes need to be considered when selecting inductance (as when operating close to current limit), but the MAX of the current limit will certainly always be used to determine the size of the inductor. 

When we start designing EMI filters, we will find that safety issues, thermal issues, and even loop stability concerns are intricately linked to the central issue of EMI. In particular, we must look closely at the aspect of safety, because even though we can attempt to sell equipment that doesn t function satisfactorily, product safety is a legal requirement without which we just cannot sell. So particularly in an off-line application, where the voltages are high enough to cause injury, safety becomes a major concern, even if we are just designing its EMI filter. 

Line to line capacitors are called X-capacitors ( X-caps ). X-caps when used in off-line applications before the input bridge must be safety approved. But after the bridge (on the rectified side), it s basically a don t care situation from the safety point of view. Note that since it is essentially a front-end component, approved X-caps are typically impulse-tested up to 2.5 kV peak. 

Line-to-earth capacitors are called Y-capacitors. Since Y-caps are critical in terms of having the potential to cause electrocution if they fail, approved Y-caps are typically impulse-tested up to 5 kV peak. Note that Y-caps used anywhere on the primary side (in off-line applications) must always be safety approved. Depending on the location in the power supply, we may even need two Y-caps in series (basically corresponding to double insulation). However, sometimes we can also find Y-caps placed between the secondary ground and earth/enclosure (for EMI suppression purposes). In this position, it is usually acceptable to use any ordinary 500 V ac rated capacitor (unapproved). 

The 3842/43/44/45 series of pulse width modulators are possibly the most popular controllers for off-line applications for several years now. Originally from Unitrode (now Texas Instruments, TI ), I can find clones from at least 12 more semiconductor companies on the web (see if you can better the count). The list may in fact be quite endless. Their quality is however often questionable, though I do admit that their Application Information seems all rather well written (hmmm, but did I read that somewhere else ). 

In this study two different flow-injection immunoassays are presented as well as the flexible automation system CAFCA (Computer Assisted Flow Control Analysis), which has been used for their control, uptake measurement, evaluation and visualization. Both immunoassays (a heterogeneous and a homogeneous assay) are based on the principles of flow-injection analysis and were developed for reliable, fast monitoring of relevant proteins in animal cell cultivation processes. Off-line applications of measurements of medium samples as well as online application during a mammalian cell cultivation are presented. All results are compared to results obtained with ELISA (Enzyme Linked Immunosorbend Assay). The requirements of the automation of flow-injection immunoassays with respect to their flexible control are discussed. 

Leung, G. and K.H. Pang (1990), A data reconciliation strategy From on-line implementation to off-line applications, AIChE 1990 Spring National Meeting, Orlando, FL... 

At present it is about to establish its dominant position as the standard analytical technique for off-line applications in laboratories of all fields of industry. 

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