INSTRUMENTATION by Ralph H. Müller
Various Devices for Information Display MONTH we attempt to cover Τ HIS some six topics dealing with some
very simple and some very elegant de vices. Several of these devices afford general information, calling attention to a situation which may or may not require a precise numerical reading to confirm the condition. One of these is a low cost Status In dicator which yields 12 message dis plays on a three-square-inch screen. As furnished by Industrial Electronic Engineers, Inc., of 5528 Vineland Ave., North Hollywood, Calif., the indicator is a small, rectangular box in which each of the 12 message positions is back lighted by an individual lamp—easily replaceable from the front. All mes sages are displayed on a single-plane viewing screen. The messages can be engraved on the viewing screen, placed on film, typed or lettered on mylar film or parchment. The 12 messages can be displayed individually, in combination, or all simultaneously. The nature of the message, except in extent, is un limited, and can be in numbers, letters, words, symbols, code, or colors. On first thought, one might infer that the device has no particular research ap plications. On the other hand, one can imagine an experiment in which some four or five variables are automatically controlled, and each controller is fitted with interlocking relays, and that, within the predetermined bounds, the relays then present a single green light or other notation on i;he Status Indica tor indicating perfect operating condi tions. This signal disappears if one or more of the variables deviates from the prescribed limits. Suitably labeled messages are then presented on the screen to indicate the source of trouble which can then be corrected and for which a precise measurement of the drift can be made. The principle of indicating a mutually satisfactory set of conditions is an old one in engineer ing, and is widely used in navigation. It would seem to have wider use in re search.
A similar application is afforded by the "Devichrome" by the Motorola In strumentation and Control Corporation of P. O. Box 5409, Phoenix 10, Ariz. Here the recorder chart system is sup plemented by a display system anal ogous to a traffic light. When the variable under measurement is on setpoint, it turns yellow or red, depending upon the magnitude of the deviation. With a large panel containing dozens of recorders, this furnishes a quick in dication of which instrument requires precise reading or appropriate correc tive action. Hunting out or locating the pointer of a d'Arsonval movement is an ancient trick. However, Assembly Products, Inc., of Chesterland 10, Ohio, has uti lized three relatively new developments to make an optical meter relay emi nently practical and compact. It is useful for continuous indication and control—without contacts. In this de vice, the pointer of the meter merely gives a continuous indication of cur rent (or voltage), but is not used to eclipse the light beam. The latter is accomplished by a mirror desk disk mounted on the axis of the d'Arsonval coil. Light from a single source is conducted to the mirror disk by two fiber-optic light pipes. Two similar light pipes return the reflected light to two photoconductivc cells. A black segment on the mirror disk eclipses the beam as the set-point is reached and operates load relays through an isolated solid state output module. The in strument can provide on-off, time pro portioning, or modulating control. Full scale sensitivity is as low as δ micro amperes or millivolts in taut-band mod els. OPTICAL POTENTIOMETER
An optical potentiometer, the Photopot, has been described by Dr. Clans H. Haake of the Transducer Division, Giannini Controls Corporation, [In struments and Control Systems 36, 6, 104 (1963)]. In the Photopot, two
strip? of metal are vacuum deposited in parallel on a photoconductor. One strip is so thin that its electrical resist ance is high (this replaces the resist ance wire normally employed in po tentiometers). The other strip is ex tremely low in resistance. If a spot of light falls on the photoconductor, it bridges the gap between the resistor strip and the conducting metal strip. When fed with low a.c. or d.c. voltages, the Photopot provides a voltage output which, in most applications, needs no amplification. Potentiometer action is achieved de pending upon where the light strikes the strip or what portion of its length is illuminated. The position of a static or moving light source can be sensed. Also, with a stationary source, the motion of a moving aperture or mask can be followed. A few of the many applications include: product line control for maintaining given geometry and shapes, microinch thickness gage, eccentricity checker, pickoff for pres sure transducers, accelerometers, gyros, borescopes, barometer-, thermometers, etc., also as a seismometric sensor, flare tracker, or sun position sensor. The Photopot has sufficient output to be applied directly to a strip chart re corder, microammeter. or voltmeter without amplification. PRESSURE TRANSDUCERS
Pressure transducers are appearing in greatly improved form and variety. As in all instruments, the improve ments are a result of new materials and new techniques. Impressive perform ance and good design characterize the instruments made by Computer Instru ments Corporation of 92 Madison Ave., Hempstead, Long Island. X. Y. These pressure transducers combine a rugged linkage-free wiper mechanism with a precision-film resistance element. They provide infinite resolution with a 10,000,000 cycle life. For gage pres(Continued on page 136 A)
VOL. 35, NO. 10, SEPTEMBER 1963 ·
129 A
INSTRUMENTATION
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FROM WESTON;
sures, two ranges are available, 0 to 100 p.s.i. and 0 to 5000 p.s.i. For gage, absolute, and differential pressures, the ranges 0 to 2 p.s.i. and 0 to 200 p.s.i. are available. The transducers have a.c. or d.c. output voltages of 50 volts for full scale. Repeatability is 0.05 per cent of full scale, frequency response is good to 200 c.p.s. Square root and other non-linear outputs can be pro vided. The total error band which in cludes linearity, repeatability, hyster esis, and friction, is 0.5 per cent. CALIBRATION
Automatic Integrator adjusts itself... from 1 mv to one volt !
The n e w Daystrom ATTEN-U-MATIC Integrator provides a u n i q u e com bination of features which offer e x t e n d e d capabilities in c h r o m a t o g r a p h y a n d spectrophotometry. Inputs r a n g i n g from one millivolt to o n e volt a r e a c c e p t e d a n d integrals c o m p u t e d without adjustment . . . t h a n k s to a built-in attenuator a n d control unit. Read, reset, hold, a n d integrate functions a r e performed automatically or m a n u a l l y . In addition, the instrument provides a d j u s t a b l e threshold setting, the capability for remote operation, a n d the sensitivity equivalent to 7,000 counts p e r second. ATTEN-U-MATIC is d e s i g n e d for u s e with the Daystrom Model 6701 single-pen recorder for m a k i n g both c h r o m a t o g r a m a n d integral d i s p l a y s on a single trace . . . integral is p r e s e n t e d a s a b a r g r a p h . A " p i p p i n g " p e n provides full-scale count a c c u m u l a t i o n . It also m a y b e u s e d with Model 6708 two-pen crossover recorder —for i n s t a n t a n e o u s d i s p l a y of both c h r o m a t o g r a m a n d integral. Daystrom Model 5593 ATTEN-U-MATIC Integrator is supplied with cabling a n d kits for a d a p t i n g it to other strip chart recorders. Features include: · Input: a c a r b o n film potentiometer s e a l e d to slidewire shaft serves a s re-transmitting slidewire. · Output: contact closure energizes p i p p i n g p e n to record full s c a l e counts, p l u s amplifier output a t t e n u a t e d for recorder display, m a y b e selected for 1, 2, 5, 10, 20, 50, m v recorder • Sensitivity: equivalent to 420,000 counts per minute · Power: 115 V a c , 60 cycles, 67 watts n o m i n a l —370 w a t t s m a x i m u m (during attenuator switching) · A c c u r a c y : attenuator c h a n g e s recorder r a n g e a n d sensi tivity of integration to VA % b e t w e e n steps. S e n d for brochure. It contains details on this u n u s u a l instrument.
WESTON INSTRUMENTS & ELECTRONICS Circle No. 8 on Readers' Service Card 136 A
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ANALYTICAL CHEMISTRY
from page 129 A)
Archbald. Pennsylvania Division of Daystrom, Incorporated
POTENTIOMETER
Physicists and chemists of our vintage can recall the days when precise poten tial measurements involved a Type Κ potentiometer, a wall galvanometer, lamp and scale, patience, and an un ruffled temperament. These things are not antiquated by any means, but for 5-digit precision, there are now many reliable digital voltmeters with auto matic polarity and decimal point in dication. As might be expected, the same elegant electronics is being used to provide d.c. for standard calibration purposes. The Kintel Division of Cohn Electronics, Inc., of 5725 Kearny Villa Road, San Diego 12, Calif., offers the Model 303 A d.c. voltage standard. This instrument is a source of precisely adjustable d.c. from 0 to 1100 volts. With seven decade controls, the read out dials permit the output to be ad justed between 0 to over ±11 volts in 1 microvolt steps; in 10 microvolts steps to over ±110 volts and in 100 microvolt steps to over +1100 volts. Accuracy is 0.01 per cent with 0.005 per cent stability. The 0.01 per cent stability for any setting is 0.0025 per cent for over eight days and to within 0.005 per cent for over 30 days. The 303A can put out 25 ma. of cur rent on any voltage range or it may be set by a panel control to 5, 10, or 15 ma. If the selected current is exceeded, or the output voltage deviates from the dial setting, an overload relay auto matically disconnects the output ter minals and causes an indicator lamp to glow. Common mode rejection is 120 db. at 60 c.p.s. Separate sampling termi nals provide effective source impedance at the load of 0.001 ohm. Comments or inquiries to Dr. Millier should be directed to his new address: Müller Research and Development Corporation P. O. Box 6157 Saute Fe, New Mexico
