WILL CORPORATION AND SUBSIDIARIES - Analytical Chemistry

May 17, 2012 - WILL CORPORATION AND SUBSIDIARIES. Anal. Chem. , 1962, 34 (2), pp 41A–41A. DOI: 10.1021/ac60182a737. Publication Date: February ...
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REPORT provides t h e power for operation of t h e r e a d - o u t device. T h i s is il­ lustrated symbolically in Figure 8,B, which p o r t r a y s the t y p e of cir­ cuit design used in several com­ mercial direct-reading p H meters [Keegan, J. J., M a t s u y a m a , G.,

THESE ARE TWO IDENTICAL IR MOISTURE TESTERS...

A N A L . C H E M . 33,1292 ( 1 9 6 1 ) ] .

Chopper Amplifier. T h e desir­ able features of t h e RC-coupled a.c. amplifier can be employed in t h e amplification of a d.c. signal if t h e latter is converted, or "chopped" into an alternating voltage. T h e design principle of t h e very widely used chopper-type amplifiers is (A) conversion of t h e p r i m a r y d.c. signal into a . c , (B) amplification of t h e a . c , a n d (C) rectification, or de­ modulation, of t h e a.c. back to d.c. Figure 9 shows t h e circuit dia­ g r a m of a commercial chopper a m p ­ lifier used as a p H meter. I t has, in addition to the features described above, t h e provision of feedback stabilization by returning t h e de­ modulated signal coming from t h e "electronic converter" in opposition to t h e input signal. T h e read-out is t a k e n from t h e feedback loop. Operational Amplifiers. One of the most recent developments in commercial amplifier instrumenta­ tion is t h e availability of a series of feedback-stabilized, d.c. amplifiers which a r e of modular—i.e., "build­ ing block"—construction, and are designed for t h e performance of v a r ­ ious analog computation operations. These are called operational ampli­ fiers, a n d t h e symbolic representa­ tions of t h e principal types are given in Figure 10. These amplifier mod­ ules are extremely useful in t h e con­ struction of experimental a p p a r a t u s , and h a v e been exploited in a n u m ­ ber of t h e electroanalytical studies cited in T a b l e I I .

ONE IS A BETTER BUY! B e c a u s e i t ' s in s t o c k a t y o u r n e a r b y Will w a r e h o u s e —like a l m o s t e v e r y Will i t e m . A n d i t ' s on its w a y in a b o u t 24 h o u r s — s h i p p e d p r e - p a i d , r e a d y - t o - u s e . B e t t e r y e t , y o u ' r e p r o t e c t e d b y Will's exclusive double guarantee . . . t h e m a n u f a c t u r e r ' s w a r r a n t y b a c k e d u p b y a n unconditional g u a r a n t e e of satisfac­ t i o n b y Will . . . a n d y o u ' r e a l w a y s w e l c o m e b a c k t o u s e t h e i n d u s t r y ' s finest service facilities. Y o u choose from a l m o s t 1000 different b r a n d s , over 20,000 different i t e m s , w h e n y o u b u y from Will. Y o u r Will r e p r e s e n t a t i v e h a s a c o m p l e t e t e c h n i c a l reference file on p r a c t i c a l l y e v e r y one of t h e m . W e like t o t h i n k y o u c a n ' t m a k e a b e t t e r b u y anywhere.

NEW! MOO RE-MIL FORD IR M O I S T U R E A N A L Y Z E R Easy, accurate readings regardless of sample density or weight. No preliminary weigh-in—simply spread thin layer of sample on t h e p a n and t h e balance automatically gives you the moisture content read t o t h e nearest 0 . 1 % . Extensive testing shows amazing repeatability of results. W h e n drying time is set a n d heater positioned, operation is automatic. Analyzer shuts itself off—answer remains until you change it. N o possibility of reabsorption or careless technique giving incorrect answers. I n stock a t your nearest Will warehouse. Write for technical literature; free demonstration on request. N o obligation.

BIBLIOGRAPHY Bair, E. J., "Introduction to Chemical Instrumentation," McGraw-Hill, New York, 1962. "Basic Electronics," Navpers 10087, U. S. Government Printing Office, Washing­ ton, D. C , 1955. Donaldson, P. Ε. Κ., "Electronic Ap­ paratus for Biological Research," Butterworths Scientific Publications, London, 1958. "Radar Electronic Fundamentals," Navships 900,016, U. S. Government Print­ ing Office, Washington, D. C., 1944. Stacy, R. W., "Biological and Medical Electronics," McGraw-Hill, New York, 1960.

Specialists in the distribution and service of scientific supplies

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WILL

CORPORATION AND

SUBSIDIARIES

ROCHESTER 3, Ν. Υ. · NEW YORK 52, Ν. Υ. · BUFFALO 5, Ν. Υ. ATLANTA 25, GA. · B A L T I M O R E 2 4 , M D . · SO. CHARLESTON 9, W. VA. Circle No. 90 on Readers' Service Card VOL. 3 4 , NO. 2, FEBRUARY 1902

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