EDITORS' COLUMN AT LEAST a rudimentary understanding of digital and analog instrumentation systems and components is rapidly becoming a necessity for the practicing analytical chemist. The unwary scientist, tempted by the many new data handling and digitizing devices available today, may incorporate an unwise combination of units into his system and actually degrade the output accuracy! In this month's Instrumentation feature, page 69A, Professor C. G. Enke of Michigan State University introduces a number of "data domains" concepts which analytical chemists will find most useful in designing and modifying analog, digital, and analog/digital measurement systems and devices. Professor Enke has for a long time been a leader in educating scientists in the intricacies of electronics. His present article provides a means of utilizing the latest electronic devices, such as digital frequency meters, signal averagers, digital pH meters, "digitized" gas chromatographs and double-beam spectrophotometers, and Fourier transform spectrometers, efficiently and effectively, with no more knowledge necessary than an understanding of the basic measurement process. In the future we shall feature, as a sequel to Professor Enke's article, a discussion and review of the analytical aspects of the digitizing step in digital instrumentation, authored jointly by Professor Stuart P. Cram of the University of Florida and Professor Harry L. Pardue of Purdue University. The quantitative aspects of digitizing and instrumentation performance and specifications will be considered for this important step prior to data acquisition or reduction. The similarities and differences between voltage-to-frequency conversion and analog-to-digital conversion also will be stressed. We hope that the two-part series of articles mentioned above will
Now, Side-window arrangement in a reliable photomultiplier tube (S-20) by Hamamatsu Expand the wavelength range of your spectrophotometer with the new HAMAMATSU R-446 Side-Window Photomultiplier Tube. S-20 response —185-850 nm. Standard direct replacement requires no adaptation. The R-446 eliminates the need for several differentrange tubes or time-consuming interchanges. When your UV spectrophotometer analyses require wider wavelength coverage, lower noise, and/or higher sensitivity, plug in the HAMAMATSU Side-Window R-446 and get all the response you need. Dependable, reliable, and available on 48-hour shipment. Write or call Dept. PT-AC11
OCLI Instruments 132 WATER STREET, SOUTH NORWAI.K, CONN. 06854 (203) 853-2224 Circle No. 6 on Readers' Service Card
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play a significant role in allaying some of the fears many analytical chemists seem to have regarding the computerization of laboratory instruments. For those who desire more first-hand information about laboratory computerization, the fol lowing meeting or the short course described below may be of interest. The Microwave Research Insti tute of the Polytechnic Institute of Brooklyn will hold a symposium on "Computers and Automata," April 13-15, 1971, in New York City. The symposium will feature sessions on basic limitations on speed and power, real-time and other time-bounded computations, artificial intelligence and computer creativity, principles of languages, programming and compiling, com puter architecture, synthesis of au tomata and logical circuit design, and machine diagnostics. For more information, contact Jerome Fox, Executive Secretary, MRI Sympo sium Committee, Polytechnic Insti tute of Brooklyn, 333 Jay St., Brooklyn, Ν. Υ. 11201. The Purdue University Chemis try Department will offer a short course on "Digital Computers in Chemical Instrumentation," June 9-26, 1971. The course is designed to provide a sound introduction to the use of the small digital compu ter in the laboratory. The princi ples and practices involved in the application of digital techniques will be discussed. Three weeks of intensive lectures will deal with the elements of digital logic, digital data acquisition techniques, and the use of the on-line digital computer in chemical instrumentation. In addition, there will be ample oppor tunity for laboratory experience with the designing of digital logic circuits, interfacing chemical instru mentation to the digital computer, and programming the small digital computer. Application forms and further information may be ob tained from Dr. S. P. Perone, De partment of Chemistry, Purdue University, Lafayette, Ind. 47907.
TAFID A hot n e w concept that's 100 times more sensitive than TGA. A n d that's only the start. Actually, TAFID (Thermal Analysis Flame Ionization Detection) exceeds TGA in six key areas. These were o u t l i n e d recently by Dr. F. T. Eggertsen and Dr. F. H. Stross in the October issue of THERMOCHIMICA ACTA*. Here is what they said: Sensitivity: " . . . is about 100 times greater than ordinarily obtained by thermogravimetric analysis." Resolution: " H i g h e r resolution is possible than in TGA because of the smaller samples that can be used . . . Effective one-plate resolution is obtainable." Specificity: " . . . is specific for reduced [ o r g a n i c ] carbon and does not respond to water, carbon oxides, nitrogen oxides and other substances normally associated w i t h inorganic materials." Analysis Time: " . . ,. capable of high speed of analysis, o w i n g to the small sample requirement and l o w thermal lag of the fur nace . . . an isothermal m o d e . . . provides especially rapid and convenient measurements." Data Readout: "is [directly] expressed as rates of evolution or integrated amounts." Applications: ' · . . . h i g h s e n s i t i v i t y a n d w i d e range o f l i n e a r response, together w i t h its specificity and uniformity of response to organic carbon, make it uniquely well suited for the quanti tative analysis of organic materials." W r i t e today if you w o u l d like a reprint of this paper and a c o m plete technical description of o u r new M o d e l 3000 Thermal A n a l ysis System . . . the only instrumentation available that incorpor ates the TAFID concept. •Fggertsen. F. T., Stross, F. H., THERMOCHIM. ACTA., 1 , 4 5 1 , (1970).
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