INSTRUMENTATION
AVCDisTS tube, sealed at the ends with trans mitter and receiver, will resonate at a frequency f0 = nc/21 where c is the velocity of sound, 1 is the length of the pipe, and η = 1, 2, 3, . . .. The velocity of sound in an ideal gas is: c = V ^ v R T / m ) where γ is the ratio of the specific heats, R is the molar gas constant, Τ is the absolute tempera ture, and m is the molecular weight. If this is substituted in the preceding equation, we have:
FROM WESTON
f0 = (1/21) V ( y R T / m )
Automatic Integrator adjusts itself... from 1 mv to one volt !
The new Daystrom ATTEN-U-MATIC Integrator provides a unique com bination of features which offer extended capabilities in chromatography and spectrophotometry. Inputs ranging from one millivolt to one volt are accepted and integrals computed without adjustment . . . thanks to a built-in attenuator and control unit. Read, reset, hold, and integrate functions are performed automatically or manually. In addition, the instrument provides adjustable threshold setting, the capability for remote operation, and the sensitivity equivalent to 7,000 counts per second. ATTEN-U-MATIC is designed for use with the Daystrom Model 6701 single-pen recorder for making both chromatogram and integral displays on a single trace . . . integral is presented a s a bar graph. A "pipping" pen provides full-scale count accumulation. It also may be used with Model 6708 two-pen crossover recorder —for instantaneous display of both chromatogram and integral. Daystrom Model 5593 ATTEN-U-MATIC Integrator is supplied with cabling and kits for adapting it to other strip chart recorders. Features include: · Input: a carbon film potentiometer sealed to slidewire shaft serves as re-transmitting slidewire. · Output: contact closure energizes pipping pen to record full scale counts, plus amplifier output attenuated for recorder display, may be selected for 1, 2, 5, 10, 20, 50, mv recorder • Sensitivity: equivalent to 420,000 counts per minute · Power: 115 V ac, 60 cycles, 67 watts nominal —370 watts maximum (during attenuator switching) · Accuracy: attenuator changes recorder range and sensi tivity of integration to Vi % between steps. Send for brochure. It contains details on this unusual instrument.
WESTON
I N S T R U M E N T S & ELECTRONICS Circle No. 133 on Readers' Service Card 130 A
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ANALYTICAL CHEMISTRY
Archbald, Pennsylvania Division of Daystrom, Incorporated
hence the resonant frequency is pro portional to -ν/Τ a r ) d is a function of the parameters of the gas. The authors have given details of a transducer of this type for the meas urement of temperature. In their case, the sensitivity attained (depending upon the length of the resonator) was 1 to 9 cycles per second for ° C. Actually, the general technique of such resonators, particularly when used with modern electronic counting techniques, can attain high precision and be employed, as the equations in dicate or imply, for such things as specific heats, the analysis of gases, liquids, or solids, or for determining elastic constants, Young's modulus, etc. Frequency measurements are easily made to 1 part in 108 or better and over a wide range of counting intervals. Once more we mention the fact that during World War I the Germans were analyzing nitrogen-hydrogen mix tures for use in the Haber nitrogen fixation process by blowing them through an organ pipe. For a pipe of fixed dimensions, the pitch or fre quency is a function of the average molecular weight of the gas mixture. The speed of sound in hydrogen is 1260 meters/second and that of nitro gen 337.5 m./sec. In the absence of fancy electronics at that time and to avoid the need for analysts with a sense of absolute pitch, a motor driven siren was used to match the tone to zero beat. TRANSLATIONS OF RUSSIAN INSTRUMENTATION LITERATURE
Another convenient source of current information on Soviet developments in instrumentation, measurement tech niques, and automatic control is Meas urement Techniques, a translation of Izmeritel'naya Tekhnika, a publication of the Academy of Sciences of the U.S.S.R. It is published and distrib uted at nominal subscription rates under a grant in aid to the Instrument Society of America from the National Science Foundation.
