A/C Interface Edited by Raymond E. Dessy
Local Area Networks: Part II The capsule reports that follow represent approaches to the problem of providing local area network (LAN) capabilities in the analytical laboratory. The contributors were invited to give the reader an exposure to alternate implementations and different site characteristics. The capsule reports build from the philosophies and vocabulary introduced in the preceding tutorial article (September issue, p. 1167 A). The purpose of these companion articles is to offer interested analytical chemists sufficient background material and to provide a spectrum of examples so they can synthesize solutions appropriate to their environments. Each laboratory has its own unique skills, needs, history, and internal structuring and requires its own individual solution. It is hoped this bipartite tutorial/capsule approach will help us better understand and control the power that computers can bring to our laboratories. The next series will address the problem of laboratory information management systems: how we store, manipulate, and retrieve the data that flow along the conduit of a local area network. The following capsules dealing with local area networks present five quite different approaches to the same problem: providing access to computing power easily and efficiently. In sequence, the reader will be exposed to solutions involving: • a mixed baseband bus network coupled to a star net; • a broadband bus network; • a ring network; • a star network coupled to a broadband net; and • a single multiprocessor center. 0003-2700/82/A351-1295$01.00/0 © 1982 American Chemical Society
Mary Kay Cosmetics, Inc. Manufacturing Group 1330 Regal Row Dallas, Tex. 75247 Contributor: Ray Miller The Quality Assurance Laboratory at Mary Kay Cosmetics provides raw material testing, bulk and finished product testing, and microbiological testing for cosmetic products and components. The two-floor laboratory is divided into analytical and microbiological sections and houses 12 scientists. Most of the analytical instrumentation is located in the lower floor lab. The upper floor contains some analytical instrumentation and all microbiological equipment. The maximum spatial separation for data transmission at this time is 100 ft. The majority of laboratory instrumentation operates either under dedicated computer control (e.g., FTIR, pulse NMR, GC data systems) or has digital communication capabilities (balances, pH meters). Few instruments require analog data acquisition. Automation of the laboratory is being handled in four stages: • elimination of paper information flow through the use of a data base management system (DBMS); • acquisition, manipulation, and transmission of data to the DBMS through a lab data system; • automatic control of instruments and autosamplers; and • automation of sample preparation. A laboratory data system needs to perform a wide variety of tasks. Communications must be established with
the dedicated laboratory computer systems, so that processed data can be passed to the Manufacturing Group DBMS. This information is compact and sporadic. It can be queued in the dedicated unit until transfer is permitted. Communicating instruments that do not have raw data manipulation capabilities need more interaction with a laboratory computer system. Control information can be passed back and forth as data are received and processed for transfer to our DBMS. Noncommunicating instruments require that a computer monitor status lines and provide control signals inside the instrument. Acquisition of digital or analog data may also be required of this computer. The system must be redundant so that in the event of a malfunction there are backup capabilities to minimize downtime and lost data. The DBMS is the recipient of all laboratory results from the lab data system. A 32-bit mini that can support up to 100 users over RS-232 lines is used for management information through an integrated manufacturing data base. The system has large disk storage and backup capabilities. Five user terminals and a printer are available in the lab for direct data base inspection and manipulation. One RS-232 line is used to communicate with the lab system (Figure 1). The lab system consists of three interconnected units: a star network topology, an IEEE-488 multidrop, and a baseband network. The star network is based on a large 16-bit microcomputer with multitasking capabilities. The
ANALYTICAL CHEMISTRY, VOL. 54, NO. 12, OCTOBER 1982 · 1295 A
32-Bit Mini
Manufacturing Laboratory
Disk Floppy
NMR
Terminals and Printers
GC Data Station
16-Bit Micro
FTIR
IEEE-488 Bus Star Network
RS-232 Density Meter
Printer
RS-422 Twisted Pair
Balance
μΟ
Floppy
-Multimeter
ρ Η Meter μΟ Balance UV/VIS Spectrometer
μΟ
LC
Printer Balance
μθ\ ρ Η Meter
LC
crocomputers in a transparent fash ion. A total of 64 microcomputers can be supported by the network. If the LAN connection fails, the ex periment is still under control of its microcomputer; data storage can occur locally. If communications are down between the LAN and star net work, data can be stored on the LAN disk. If the LAN disk is down, data can be sent to the star network for storage. The star network is not abso lutely crucial since each dedicated sys tem can hold data until communica tions are reestablished. Staff members directly involved with implementation and mainte nance of the system are: one full-time chemist with instrumentation back ground and one full-time analytical chemist with formal instrumentation training and a microcomputer hard ware and software background. The development of this system is based on two premises: • More distributed processing re sults in faster response to user de mands and less critical downtime for any unit. • Software cannot circumvent hardware design limitations—highly flexible hardware allows software to be optimized for the application.
Union Carbide Technical Center South Charleston, W. V a . 2 5 3 0 3
Microcontroller
Contributors: N. Bruce Angelo, T. Sloan, and Wayne G. Nunn
Disk IEEE-488 Bus
Floppy
Baseband CSMA Local Area Network
/LtC
juC
AA
μΟ
Balance
Temperature System
Figure 1 . A m i x e d b a s e b a n d / b u s n e t w o r k c o u p l e d t o a star net; Mary K a y C o s m e t ics M a n u f a c t u r i n g G r o u p , μ ϋ = m i c r o c o m p u t e r
system has a 10-megabyte Winchester disk, dual 1-megabyte floppies, a color printer, and a 700 X 500 pixel graphic display. Five RS-232 lines are avail able for controlling communications with dedicated computers on the FTIR, NMR, and GC data systems. This microcomputer has an IEEE488 interface controlling a multidrop bus to which liquid chromatographic equipment is attached. The baseband carrier sense multiple access (CSMA) LAN allows for data
acquisition and control of instrumen tation over customized microcomputer interfaces. Each microcomputer is an 8-bit system with keyboard and 192 X 256 pixel graphics. The micro can be a user-interactive instrument controller or a terminal to the network. This ba seband net implementation allows communication over a twisted pair of wires at 1 M bit/s through distances of greater than a kilometer. A 20-megabyte disk drive with backup capability will be accessible from all of the mi
1296 A · ANALYTICAL CHEMISTRY, VOL. 54, NO. 12, OCTOBER 1982
Richard
At Union Carbide's Technical Cen ter some 900 professionals, techni cians, and support staff form the Re search and Development Department for two of Union Carbide's major busi ness divisions. Fundamental and busi ness-directed research as well as pro cess development are distributed among four major laboratory/office buildings and numerous satellite buildings throughout the 670-acre site. Numerous computers are already used within R&D for process manage ment and control, automated instru mental analysis, interactive/timeshared/batch data processing, infor mation storage/management/query/ retrieval, word processing, and various other computer-aided activities. Until 1981, communication with and among the several systems and services was by individual twisted-pair cable or telephone company circuits. In mid-1981, following a year of study and design, an LAN employing rf broadband technology was placed in service to provide communications fa cilities to every laboratory module, of fice, and work station in all 16 build ings of R&D. During the study phase, the choice
of the technology to be employed was governed by a variety of requirements and constraints. Communication paths were required to support: a dis tributed network for process manage ment and control; a distributed net work supporting intelligent instru ments and research laboratory com puters; a large, dedicated data collec tion and processing system supporting a chromatography skill center; termi nal access to any of the above net works; interactive gateways to other corporate computing services; and of fice automation services. The design was constrained by re quirements for minimum single points of failure, high noise immunity, and ease of installation and maintenance. The communications technologies considered were direct-connect twist ed pairs, telephone circuits, micro wave, fiber optics, baseband, and broadband. The direct-connect twisted-pair op tion was eliminated quickly. The Technical Center's underground utili ty conduits were almost filled to ca pacity. The rate of growth in the num ber of computers and intelligent de vices requiring communication ser vices indicated that any reasonable addition to conduit capacity would not be adequate for very long. Directconnect twisted pairs would offer little immunity to electromagnetic interfer ence. The reasons for eliminating phone circuits were essentially the same as for direct-connect twisted pairs. Microwave transmission, at least between buildings, was considered, but appeared to be an expensive alter native. In addition, a licensed engineer would have been needed to service and maintain the equipment, and a station license would have been required. Fiber optics appeared very attrac tive because of its immunity to electri cal noise and consequent low bit-error rate. However, frequent repeaters would have been necessary. In addi tion, multidropping of fiber optics ca bles was not possible. Baseband and broadband appeared to be the only viable alternatives. One drawback of baseband was its distance limitation. Another was that it allowed only one user at a time the use of the cable. Simultaneous paths were re quired for multiple real-time data ac quisition systems and many concur rent interactive users. Radiofrequency broadband was chosen as the commu nication medium for the R&D LAN. Broadband permits both frequency di vision and contention access multi plexing. Therefore, many channels can coexist simultaneously on one cable. Broadband uses hardware common to the cable television industry, and cable, amplifiers, couplers, splitters,
DEC PDP-11/70
Unibus
Network Manager
KMC-11
Loop Interface In Clock
Out Clock
In Data
Optical Isolation Out Data Loop Sink
Coax
Loop Source
Power from Terminal(s) Down Data
Active Tap
Loop Power Source
