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NESLAB MODEL TE9
IMMERSION COOLER 1/6 H.P. air cooled hermetic compressor Immersion Head 7 / 8 " χ 5 " long Continuous operation USE W I T H A N Y BATH T O A C H I E V E BELOW A M B I E N T T E M P E R A T U R E S Write us for complete
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heights varied an average of ±0.1%, the greatest individual deviation being 0.9%. Actually, the overall system fidelity exceeds somewhat our expectations. Dc drift and ac noise in the inexpen sive operational amplifier circuits and in the signal conduction paths (some times as long as 30 meters) associated with the interfacing hardware normal ly have proved to be somewhat less than the corresponding quantities produced in the GLC and autoanalyzer detectors. Regardless of the source of analog noise, the digital filtering procedures seem adequate to elimi nate untoward consequences of such noise with the wide variety of instru ments employed, so that the ADP data reduction mode is applicable to most data acquired. However, it should be emphasized that, in our rather poor electronic environment, digital filtering is crucial to routinely realizing good computerized data pro cessing results (such as shown in Table II) with the ADP mode. Without digital filtering, some of the ADP data reduction routines would be "fooled" occasionally by noise spikes or the like, leading to the necessity for more extensive use of the slower, less precise IDP mode. This is illustrated in Figure 4 which shows an example of the effects of the digital filtering operation on a typical GLC peak (a portion of a larger data array). The original raw data in Figure 4 show one large noise spike on the peak which is typical of what is occasionally encountered (about 95% of our chromatograms are free from such arti facts) as a result of power line tran sients induced by solenoid activation and the like. The obvious option of power line conditioning was deter mined to be less cost effective, as well as less electronically effective than the above-described software filter de signed to eliminate noise spikes. In ad dition to the only occasional noise spikes, the more common forms of random noise evidenced in the raw data of Figure 4 are sufficiently re duced to make the data compatible with the subsequent data reduction strategies. We consider digital filter ing to be a valuable part of computer ized data processing. It provides the basis for using with good fidelity the relatively simple data reduction soft ware which is more efficient regarding core and operating time than more so phisticated options, and it achieves this at lower cost than the electronic hardware options for improving sig nal/noise characteristics.
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Conclusions
The minicomputer system as de scribed has automated data acquisi tion and determination of peak posi-
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MINIATURE VALVES AMD FITTINGS
2, 3, and 4-way models
Every inert component you need to quickly construct any liquid or gas flow system.
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COMPLETE CATALOG on request
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CIRCLE 204 ON READER SERVICE CARD A N A L Y T I C A L CHEMISTRY, VOL. 47, NO. 3, MARCH 1975 · 373 A
