INSTRUMENTATION

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INSTRUMENTATION The increasingly important role of instrument scientists in the development of all sciences requires an extensive curricuium for adequate professional training by Ralph annual instruments issue of Science [110, N o . ΎΙiHE 2858 (1949) ] contains a n u m b e r of articles which, we believe, will interest t h e analyst. I n t h e first of these, E . XL Condon, director of t h e N a t i o n a l B u r e a u of Standards, raises a question t o which we supplied an affirmative answer ten years a g o : " I s there a science of . instrumentation ? ' ' Science

of

Instrumentation?

H e has shown convincingly t h a t "in modern complex instruments a large p a r t of t h e instrument is independ­ ent of t h e quantity t o be measured. I t is this fact t h a t is giving rise t o t h e recognition t h a t there is a science of instrumentation concerned with these common ele­ ments a n d their systematic study a n d improvement. I t seems quite likely t h a t t h e instrument scientist will, in the future, play a role of steadily increasing impor­ tance in the development of all t h e sciences. I t is a pro­ fession t h a t should lend itself t o specialization and work-

MM.

ail iiii 3Mmller

ers in all fields should be relieved as m u c h as possible from t h e distraction of having t o devote too m u c h a t ­ tention t o t h e detailed design of instruments for their particular needs." According to D r . Condon, these ideas are t o be defi­ nitely implemented b y t h e Bureau of S t a n d a r d s in co­ operation with t h e Office of N a v a l Research a n d re­ search groups in t h e A r m y a n d Air Force. T h e objec­ tives of this program are t h r e e : (1) systematic analysis of available methods a n d devices in terms of their pre­ cision and reliability; (2) studies of materials, compo­ nents, and elements which are now known to impose serious limitations on i n s t r u m e n t a t i o n ; and (3) devel­ opment of specific instruments not now available. We are in complete a n d enthusiastic agreement with these s t a t e m e n t s and policies, b u t wish to repeat t h a t a profession cannot exist without a d e q u a t e professional training. Consequently, We have been asking, b y w h a t type of academic osmosis are t h e prerequisites for this profession to be absorbed from our present curricula? T h e answer is evident: I t can be achieved only b y an extensive, detailed cur| riculum directed precisely t o this ) end. Our guess is t h a t it will re­ quire another decade before this is completely recognized and, in t h e interim, we shall t r y our best, as | individual resources permit, t o ac| quaint our students with t h e al1 ready bewildering a r r a y of instru| m e n t s a n d techniques. I n so do­ ing, t h e student will become an in­ terim technician, still baffled by t h e I intricacies of "black-box" magic. Universal

Figure 1.

•1

Amplifier

A most versatile laboratory in­ strument has come to our a t t e n t i o n which should be almost indispensa-

Universal Amplifier 23 A

ANALYTICAL

24 A

New-... TRIPLE-ACTION ALL-PURPOSE Zmsse®®**

DRYER!

N o w available! A n all-purpose Dryer (or the Laboratory, with fingertip three heat control, an exceptionally low priced instrument with the following features: •

FINGERTIP CONTROL

•

CONTROLLED AIR DIRECTION

•

LOW COST

•

DURABLE CONSTRUCTION EASILY CARRIED

• •

ONE YEAR GUARANTEE

•

SMART APPEARANCE

d o w n w a r d as well as t w o horizontal levels. Actually provides three times the air flow o f other c o m p a r a b l e blowers. This d r y e r is manufactured to precision standards f o r longer service. Its mechanism is engineered t o o p e r ­ a t e simply a n d effectively a t the touch o f a finger. Beautifully finished in gleaming chrome trim and f u l l y g u a r a n t e e d f o r one y e a r .

SPECIFICATIONS: " L o " Heat " H i " Heat 600 watts 1200 watts 2050B.T.U. 4100B.T.U. 103 F. 134 F. 8750 2750 837 837 175 175 CURRENT—50/60 cycle A . C . only CORD—Length 7 ft. U.L. approved FAN—Blower type

Temperature ( 1 2 " from nozzle) RPM 2750 Velocity FPM 837 Volume CFM 175 Switches 2-1 5 amps MOTOR—Heavy duty 2 pole, 2 coil induction type VOLTS—110/120 FINISH—Three dimensional baked enamel with chrome trim. DIMENSIONS—Height overall 9y 4 », length 1 1 " , width 5Vs". N o . AC-11809 Triple-Action Dryer

ARTHUR S. LABORATORY

, $14.95

e

LaPINE APPARATUS

127 W. Hubbard St.

INSTRUMENTATION

ble for electrical measurements of analytical and general nature. I t is the Millivac Universal d.c. amplifier T y p e DCA-3 made by Millivac Instruments, P.O. Box 3027, New Haven, Conn., shown in Figure 1. I t is a truly universal d.c. amplifier with widely variable input and o u t p u t circuits as well as adjustable gain and feedback. A 120-cycle modulator converts incoming d.c. voltages into a carrier signal which is amplified, rectified, and metered. There is sufficient amplifier gain to drive the instrument to the very limit of permissible modulator noise, hum-pickup, and tube noise. With an external output meter of 0 to 200 microamperes, this limit will be reached with approximately 1 mv. full scale input. Some of this instrument's features include: 1 mv. full scale, with sensitive output meter. High input im­ pedance—6 megohms directly, 16 and 60 with multiplier (1 to 1 and 1 to 40,000). Adjustable negative feedback for accuracy and linearity. Input impedance selector, 100 ohms to 4 megohms parallel burden. Output shunt selector, 1 ohm to 1000 ohms, parallel burden, for protection of sensitive output meters. Wide input range—0.05 mv. to 1000 volts, and ΙΟ" 11 to 10~ 4 Â. An arrangement for mid-scale zero setting for bridges and similar applications. Polarity pulse, for indicating polarity of signal. Stable zero, no readjustment required above 10-mv. full scale. 5-ma. maximum d.c. output, sufficient for ink and photographic recorders. A carrier output at 120 cycles for higher current outputs with universal transformer.

Here is α Dryer-Blower f o r the L a b o r a ­ t o r y that has all the features you have been looking for. Three heat f i n g e r t i p control provides cool, t e p i d or w a r m air for d r y i n g in a matter o f seconds. ^ W o r k s s p e e d i l y a n d effectively. The a p p a r a t u s is useful in hastening many d r y i n g chores in the l a b o r a t o r y includ­ ing d r y i n g glassware, metallographic specimens, etc. Highly effective in a i r - s w e e p i n g . M a y b e used as an exhaust b l o w e r . This t r i p l e service unit comes e q u i p p e d with a col­ lapsible stand f i t t e d t o the base per­ mitting o p e r a t i o n in 4 different posi­ tions. It is easily directed u p w a r d or

Cooling

CHEMISTRY

& COMPANY

INDUSTRIAL

CHEMICAL

Chicago 10, III.

This amplifier is well suited for industrial or laboratory use. I t can be preset at the factory for a specific application, but in the laboratory, where a wide class of measurements are required from time to time, its flexibility is a great asset. T h e output can accommodate almost any device from a sensitive galvanometer down to robust recorders or relays. In the case of a.c. relays the a.c. o u t p u t of the amplifier is used to advantage. Another useful feature is a built-in 10-mv. d.c. calibration circuit accurate to 1%. With this signal set in, the o u t p u t meter can be set to any desired specific point on the scale such as mid-scale, full scale, etc. This automatically calibrates all other voltage ranges provided by the multiplier switch. T h e possibility of adjusting amplifier gain and feedback is a useful feature, because the improved linearity obtained by feedback results in a gain loss, and if the latter can also be adjusted, the optimum conditions for a given problem can be set in rapidly. A feedback release control is also provided whereby "locking-in" at extremely high feedback can be interrupted. A useful accessory is a shunt box with 23 ranges from 165 X 10~ 12 A. to 10 amperes, full scale. The Millivac instrument and shunt box has found wide application in electronic, general chemical, analytical, biophysical, and biochemical work. The amplifier, as shown, is operated directly from the 115-\"olt 60-cycle line. I t s dimensions are 1 5 X 9 X 7 inches.