Optical encoder

Figure 5.17 Stability of optical encoding towards oligonucleotide reagents. Organosilica microspheres covalently labelled with ATTO 550 dye are stable towards each of the reagents used in phosphoramidite oligonucleotide synthesis. In contrast, optically encoded polystyrene-divinylbenzene (DVB) beads are unstable in most steps, in particular those involving dichloromethane and tetrahydrofuran. (Reproduced from ref. 28, with permission.)...

It s not very difficult to do adjustable electronic ignition timing by yourself with an optical encoder connected to the engine shaft, but I d rather get a finished product if available. 

The critical phase of either a creep test or a stress relaxation test is in the first few seconds. It is here that the transducer can be overloaded or the optical encoder can give a noisy response. Most controlled-strain instruments will give an audible error signal if the transducer is overloaded. For controlled-stress instruments, the noise level is determined by the resolution of the optical encoder. 

Linear position Linear motion is typically driven by the use of lead screws, ball screws, or worm drives with ranges from less than a 25 mm to over 6 m. Linear sensors for position feedback in the lower range include LVDTs, magnetic, and optical encoders. For longer strokes, the linear feedback devices include encoders and magnetostrictive position transducers. Optical encoders are practical up to 2 m. Magnetostrictive position transducers can be used up to 20 m. 

The drawback of an incremental encoder is that the count can be corrupted by power interruption or electrical noise. Then, in order to restart the system, it needs to be homed to re-establish the zero count position. A pictorial representation of an incremental rotary optical encoder is shown in Figure 3.157. 

In an optical encoder, a linear pattern or rotor disk is provided with adjacent transparent and opaque sections, allowing pulses of light to reach the detectors as the move progresses. These light pulses produce the electrical output pulses that indicate the linear or angular position change and direction. 

A recent patent by Kaye and Tracey [71] reported intriguing applications of material sciences techniques for the preparation of optically encoded machine-readable solid supports. The most relevant features of some of the patent embodiments are presented and briefly discussed (see the original patent [53] for more detailed descriptions). 

Xiao X, Zhao C, Potash H, Nova MP, Combinatorial chemistry with laser optical encoding, Angew. Chem. Int. Ed., 36 780-782, 1997. 

Nicolaou KC, Pfefferkom JA, Mitchell HJ, Roecker AJ, Barluenga S, Cao GQ, Affleck RL, Lillig JE, Natural product-like combinatorial libraries based on privileged structures, 2, Construction of a 10,000-membered bcnzopyran library by directed split-and-pool chemistry using Nanokans and optical encoding, J. Am. Chem. Soc., 122 9954—9967, 2000. 

In the laboratory we have several automatic and semiautomatic robotic apparatus including the IRORI Nanokan optical encoding system for split- and pool-synthesis (34) and synthesizers from Advanced ChemTech and the MiniBlock from Mettler, Toledo, OFI. 

Fiorini, C., Charra, F., Nunzi, J.-M., and Raimond, P. (1997). Quasi-permament all-optical encoding of noncentrosymmetry in azo-dye polymers./. Opt. Soc. Am. B 14, 1984-2003. Fiorini, C., Charra, E, Etile, A.-C., Raimond, R, and Nunzi, J.-M. (2000). Photoinduced non-centrosymmetry in azo-polymers using dual frequency interferences. In Advanced functional molecules and polymers (H. S. Nalwa, ed.), pp. 167-216, Gordon and Breach Science Publishers, Amsterdam. 

S. Nie, M. Han and X. Gao, Lab-on-a-bead optically encoded microspheres for massively parallel analysis of genes and proteins. Abstract Paper—American Chemical Society, 221st IEC-019, 2001. 

Radiofrequency tags encapsulated in grafted functionalized polymers have recently been reported (53), as have laser optical-encoded ceramics with grafted polystyrene supports (54). These devices have the properties of really big beads that contain the identifying tag and thus combine the features of chemically encoded libraries with the advantages of mechanically encoded libraries. 

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