by D. K. Sweeney, International Business Machines Corp., and has the I B M designation H864. This procedure employs floating decimal arithmetic and mathematically involves Gaussian elimination in the matrix inversion. For the purposes of this application, the inversion program was modified for reconversion from floating decimal to fixed decimal before punchout of the in\-erted matrix. Various other reading routines were added. Additionally, the drum clearing routine \I-as modified so that the direct matrix prepared in the computer lvould not be lost. Inasmuch as floating decimal arithmetic was involved, the last operation in the assembly of the direct matrix is conversion from the fixed decimal t o the floating decimal notation, by insertion of a “floating decimal” instruction card a t the end of the assembly problem. Following this point, the inversion program may be fed
to the computer if desired and inverses thereupon obtained.
CONCLUSIONS
K h a t is obtainable through use of the matrix assembly program discussed above? First, one may have a tabulation of the direct matrix as shown in Table V. This tabulation was prepared with a specially wired board for an I B M 407 tabulating machine. Secondly, much manpower is saved (Table VI). Regardless of the matrix size, considerably less effort is required when the digital computer is used for assembly of the calibration information. For the largest matrix assembled by this procedure, approximately 12 additional minutes of the computer were required for the assembly over and above the time required in the computer for the inversion and miscellaneous operations
employed in earlier schemes. At the same time, the man-hours requirement was decreased from the neighborhood of 30 t o less than 2 hours. For smaller matrices, the decrease in man-hours was less, as might be expected, but the added convenience is still appreciable when the machine assembly procedure is used. The computer times of 0.6 and 0.3 hour noted in Table VI may seem unusually long for inversions. Several additional operations are conducted with the larger inverse matrix data before actual use in computation programs for analytical problems. These operations are not appropriate for consideration in this paper.
RECEIVED for review December 26, 1957. Accepted March 11, 1958. Division of Petroleum Chemistry, S mposium on Applications of Machine %mputation t o Petroleum Research, 132nd Meeting, ACS, New York, N. Y., September 1957.
End of Symposium. Other papers in this symposium are printed in the M a y 1958 issue of lndostrial and Engineering Chemistry
Ana Iytica I Laboratory Operation and Control Utilizing Busi less Machine Punched Card Procedures L. M. ADDISON, E. H, SPENCER, and E. M. CHARLET Esso Research Laboratories, Esso Standard Oil Co., Baton Rouge, l a .
b An IBM system for keeping track of samples submitted to an analytical laboratory, for recording results, and for reporting the answers reduces the manpower expended in record keeping and improves service to customers and the efficiency of scheduling work. Past results may be retrieved from the files with little effort and may b e searched for b y sample serial number, specific sample description, type of sample, or answer. Summary data on the performance of the laboratory are invaluable for controlling operating costs.
T
HE analytical laboratory of a modern petroleum refinery or research organization must perform daily a wide variety of tests on ever-increasing numbers of samples. Consequently, careful attention must be given to sample and data handling, to test scheduling, and to regulation of the analytical load. The analytical section of the Esso Research Laboratories a t the Esso Standard Oil Co. refinery, Baton Rouge, La., is currently using a system based on the use of business machine punched cards and accounting equipment to facilitate its operation. This
procedure was devised for use in a research laboratory. As a result, the problem of immediate reporting of test results to refinery units was of limited importance, so that it was subordinated to problems of priority, efficiency, and backlog. However, only small modifications to the system are required to meet the needs of the typical refinery laboratory. The wide scope of analytical requirements does not alter the primary aim of an analytical laboratory: to provide accurate, precise analyses. Nonetheless, it has become highly desirable to attain maximum efficiency, which, in turn, cannot be computed solely in terms of the analytical group. Maximum efficiency from the over-all vienpoint is composed of many elements, including :
1. Efficient use of manpon.er through proper scheduling. 2 . Service consistent with the needs of the production and research units. 3. Reduction in nonproductive manual effort, such as in record keeping. Providing more efficient use of manpover and better service requires that detailed information concerning the analytical situation be made available
to the laboratory management. Such record keeping tends to increase the overhead enormously if it is done manually. The problem, however, is parallel to those occurring in accounting and inventory control. Hence, it is entirely reasonable to expect benefit from the use of punched card accounting and control procedures. This report describes the integration of such equipment and procedures into the saniplehandling and data-reporting systemof an analytical section of a petroleum research laboratory. SAMPLE AND DATA HANDLING PROCEDURE
The first problem in an analytical group is the mechanics of transporting samples from the research or production groups to the analysts and then returning the test results to the proper persons. This should be accomplished routinely in as short a time as possible, with the use of a minimum of manpower. Yet, care must be taken to prevent lost or broken samples and to avoid deterioration of samples which are sensitive to heat or storage. A means must be provided t o expedite critical or “control” samples which must be analyzed immediately to provide information for control of VOL. 30, NO. 5, MAY 1958
e
885
,
DATA RECEIVER
I
Figure 1 . Data reporting and filing system Flow of samples, punch cards, and report sheets
ASSIGN UB. NO.
’
~B*IpLElllwuLIwcl/--l “LE, I
TABUUTING ROOM 1 KBYPUWCH MASTER CARDS 2: PREPARE ANALYSIS CARDS 3 . TABUIATE DATA ON REPORT SIIEETS 4. FILE COMPLETED ANALYSIS CARDS
~
SAMPLE ORIGINATOR
Id
1. DISTRIBUTE PORTIONS TO PROPER LABS 2. STORE, COMPOSITE OR DISCARD ANALYZED
STOUGE
I
LABORATORIES INDIVIDUAL
I operating units. The proper achievcment of these aims requires that a wealth of detailed records concerning this sample and data flow be made available to supervisory personnel in the analytical group. I n Esso Research Laboratories, it has been demonstrated that a punched card system provides an economical means of folloning the progress of samples through the laboratories, recording the results of analyses, and mechanically reporting these ansners to the sample originator. It also provides a complete and accessible file of all analytical data. The operation of this system is shown by the flow sheets reproduced in Figures 1 and 2. Sample Submission. A person n ho submits a sample for analysis attaches two tags as illustrated in Figure 3. One of these is a n ordinary shipping tag. known as t h e “permanent tag,” n-hich is not removed from the sample until t h e sample is discarded. The other is a punch card, the “master card,” nhich is detached in t h e sample receiving room and used t o initiate the progress of information concerning the sample through the nieclianized control system. The punch card is protected by a plastic envelope. Both the punch card and permanent tag are filled out with the same information, to eliminate any manual transcribing of identifying data by the analytical group. A pickup man collects such qamples from conveniently located collection stations on an hourly basis and transports them to the sample receiving room. Sample Receiving. One nian is assigned t o receiving and splitting samples for distribution to the various laboratories. Upon receipt of a sample, t h e tags are first checked for discrepancies in description and stamped each n i t h t h e same nuniber ( d n 886
ANALYTICAL CHEMISTRY
alytical Lab. Suniber), using a sequential numbering machine n-hich repeats t h e same number tn-ice before stepping to the next higher number. The punch card is then detached and sent to the tabulating rooni for processing. If the sample requires analyses from more than one laboratory or many analyses from one laboratoryj it is split into the required portions, each labeled with a test check-off tag as illustrated in Figure -I. The onl\ identification carried on this tag is the laboratory number. These saniplcs arc distributed to the proper laboratory on an hourly
schedule. 11-here a shortage of sample requires transmit,tal of the sample among various laboratories, the checkoff tag is marked “Return to Sample Coordination.” Ppon its return from one laboratory, the sample is reroutrtl by the saiiiple receiving man to t h e next laboratory involved. Preparation of Analysis Cards. The sample description written on t h e master card xhich \vas detached from the incoming sample is machine keypunched into t h e appropriate columns on this same card (Figure 3). I n addition t o the sample description furnished by t h e sender, a tm-0-digit code (Code A) is keypunched to identify the experimental group or pilot unit responsible for the sample. This facilitates sorting and filing of cards into categories based on the various laborabory research and development projects. Code C is used to identify t’he type of sample. The date of sample receipt is punched into the card as the chronological day of the year. This punched information is printed across the top of the card n i t h a punched card interpreter to permit visual reading for verification. This master card is nolv ready to be used as a stencil for punching the sample description into analysis cards representing each of the tests to lie performed on the sample. TKOtypes of analysis cards are used (Figures 5 and 6). Each test requires its on’n card or cards. The type A card is used for tests producing a single answer, such as gravity or sulfur.
4-
HANDLING
HANDLING
MATCHED O W INVENTORY CARDS TO DISCARD
I I
/ /
/ /
, , , . , ,
/ / /
I
DAILY BECOU) or IUCOYIIIO
AIIALYUBU
’1
I I
0
f
’ DAILY
’
BECOBD 01
ALL ANALYSES lNCOYPuTED
I I
4 INSTRUCTION8
I I
1 TO LABORATORIES L A B O M T O R Y COWTROL
-
- - - - - - - _ -I
WEEKLY h P O R T TO MANAGEMENT
Figure 2.
Operation of analytical group Tabulating center
A
Figure 3.
Sample submission tags of data reporting and filing system
A.
Master tag, showing description and analyses requested for a typical sample. This card has been punched, interpreted, and is ready to b e used far gang punching analyses cards, after which it will b e returned to sender. 6. Permanent tag, filled out as though it were to accompany master tag
SAMPLE
TAG
r m ASH DRY
[U A R O M . s m , I U
C L O U D PT.
C R Y S . PT.
zu.:
iU MELT.
PT.
B
Tests producing multiple ansn er5 use type B cards-for example. a n M T 3 I tlistillation requires t n o multiple answer cards. A supply of analysis cards is prepared in advance for each type of test d i i c h may be requested. This involves punching the test name into aiialyqis card blanks and printing this riaiiie in the proper space on the card v i t h a puiiched card interpreter. A tcqt code number is added for convenieiicc. in sorting, and the man-hour requirement for the test is added for accounting purposes. The cards are provided I\ ith spaces for iiidicatiiig the nnnlysis result along with other prr-
Figure 4.
Test checkoff tag
tiiient inforniation such as test conditions, prc'cision, and analyst identification. This information is entered on the card by marking a short line x i t h a graphite pencil through the proper numbers. Figures 7 and 8 illust,rate hon- answers are niarlred on thesf cards. The procedure for preparing analysis cards for a specific sample is as follon-e: Select a prrqxwhed but othern-is(, blank analysis card representing each test called for on the niast'er card.
Place these with the punched master card and, using a reproducer, gang punch the description from the master card into each of the analysis cards. The punched description is printed across the top of the analysis card u-itli a n interpreter. as illustrated in Figure 7 . This analysis card preparation is in reality an efficient procedure, as a group of master cards are keypunched and the required analysis cards are selected and stacked so that each master card is folloned b y its analysis cards. This interspersed card arrangenient is then run through the reproducer in one operation. Preparation of 100 to 200 analysis cards from 50 unpunched master cards requires sonie 30 niinutrs. A complete reproduction of all prepared analysis cards is next made. to produce a card imentory record of all incompleted analyses. This inrentor!. file is kept current by matching out all completed analyses on a collator. The analysis cards are iiow sorted out by laboratory and distributed t o the appropriate laboratory foreman. The niaster cards are returned to the sample originator as a receipt for the sample and for verification of tlip puiiehecl and interpreted information. Laboratory Procedure. The samples and the corresponding analysis cards have been sent to t h e laboiatory from tm-o different points and probably a t diffeient times. At fiist glance this might appear to be confusing, but in piactice it facilitates scheduling. The samples, which were niarked in all cases n i t h the laboratory number and test required. are placed in storage racks according to the analyses to be run. Each laboratory forenian has anal! sis cards representing all the anal>ses that h a l e not VOL. 30, NO. 5, MAY 1 9 5 0
b
887
Figure
5.
Blank analysis card
This type of analysis card is used for all single answers
Figure 6.
Blank analysis cards
This type o f analysis ca'rd is used for multiple answers, such as Engler distillations, Pod analyses, Burrells, or glass still reports
Figure 7.
Analysis card (analysis completed)
This type o f analysis card i s used for all single answers.
888
ANALYTICAL CHEMISTRY
I t has been filled in with the value of
34.8' API
Figure 8.
Analysis card (analysis completed)
This type of analysis card is used for multiple answers, such as Engler distillations, Pod anolyses, Burrells, or gloss still reports
yet been run. After consideration of these, he selects cards for the particular analyses on specific samples which he wants each analyst t o run. The analyst selects the sample containers corresponding to the cards assigned t o him, performs the analysis, marks the a n w e r on the card, and turns it in. If additional analyses are requested, the sample is returned to the storage shelf for redistribution. Honever, in case this is the last analysis (each checked analysis on the checkoff tag is circled by the analyst performing the test, so that the remaining analyses can be determined a t a glance) requested for the sample, it is placed in a “return to storage” basket for eventual return to the Sample Coordination Center for final storage. Each day, all completed analysis cards are returned to the Tabulating Center. The laboratory foremen can make definite Kork assignments with a minimum of effort but in an extremely clean manner. Extra record keeping in the laboratories is discouraged to avoid wasting time. Tests t h a t do not require calculation, such as gravity, aniline point, and distillation, are marked directly onto the cards after the proper measurements are made. Test data that require calculation to arrive at the final answer are entered in a notebook. However, no sample description other than laboratory number is recorded. I n addition to the analysis cards, each foreman is provided daily with an inventory (Figure 9) of all incompleted analyses. This inventory carries the date upon which the sample was submitted in addition to the complete description. Comparison of the inventory sheet with the cards on hand points out missing analysis cards. The inventory date column provides a reminder of samples that have been on hand an undue length of time.
Data Reporting. The completed analysis cards are returned to t h e Tabulating Center. The date of return is gang punched into the cards, so t h a t elapsed time measurements may be made directly by machine, subtracting date in from date out. The marked answers are converted to punches in the cards by a mark sensing device on the reproducer. They are then arranged so that all analyses for the same person are grouped together by means of a sorter. The sorted cards are run through a tabulator t o prepare separate report sheets for each data recipient. A general practice is made of putting all samples for a given person in his Run KO.order. Figure 10 illustrates a typical report sheet. There are three results columns headed “Number,” “Weight yo,” and “P.P.M.” This arrangement minimizes the printing of units from the analysis card. Most results going into the numbers column are in units well understood by all, such as bromine number, octane number, or ASTRI gum. \There a m biguity exists, as in an analysis for the total quantity of H2S in a gas sample, the analysis name carries the units as: H2S,mg./100 ml. Inventory and Data Files. T h e duplicates of analysis cards constitute the inventory file. This file is maintained in a definite sequential order as follotvs: Main grouping 1st subgrouping 2nd subgrouping 3rd subgrouping 4th subgrouping
By laboratories By research units By test By sample type By laboratory sample number
Thus, tabulating the inventory file gives a separate inventory listing for each laboratory. The outstanding tests for each research unit are grouped together for ease in controlling the elapsed time according to priority
assignment on work for each group. As man-hours for each test are carried on the analysis cards, the tabulator will give the total and subtotals of manhours represented by the inventory. Completed work is withdrawn from the inventory daily by arranging the daily completed analysis cards in the inventory order and removing matching cards n-ith the collator. The matched out inventory cards are discarded, while the analysis cards are filed by research unit. Sample Storage. After all analyses have been run on a sample, it is returned to the sample receiving room for storage. A record of stored samples is provided in the following manner.
A duplicate is made of the master card for each sample. These cards are retained in a n abeyance file in the sample room until a sample represented by a particular card is returned to storage. The card is then placed in a storage file, n-hich may be machine tabulated to indicate what stored samples are on hand. Samples are discarded after 6 months’ storage, unless specific instructions to the contrary are received. ilt this time, the storage cards for discarded samples are destroyed. Rush Samples. Analyses t h a t are iieeded urgently t o furnish pilot plant operating information may be marked “Control.” This constitutes authority to give the sample completely top priority, with no regard for inefficiency t h a t such rush treatment may cause. The control label is a signal for the sample receiver t o transmit the sample immediately to the proper foreman without removing the master tag. The foreman has the sample run as soon as he receives it and telephones the data to the interested person. The answer is also marked on a completely blank analysis card, which is VOL. 30, NO. 5, MAY 1958
889
Run
Report To IXH
Cnit INV
API API API API A PI API API API API API BPI API API API API API API BPI 4PI API
ESSO ESSO ESSO ESSO ESSO ESSO ESSO ESSO ESSO ESSO ESSO ESSO ESSO ESSO ESSO ESSO ESSO ESSO ESSO ESSO
100.1
LRIA LMA LILA
STDOL STDOL STDOL STDOL STDOL STDOL STDOL STDOL STDOL STDOL STDOL STDOL STDOL STDOL STDOL STDOL STDOL STDOL STDOL STDOL STDOL STDOL STDOL
12i-1 127B 128.1 128-4 129-1 129B 128B 127A 127B 128'4
tllh
LM.4 LMA
LMA LMA LRfA
LlI.4 LIfA
LlIA
LM.4 LJfA LJlA LM.4 LMA LMA LRIA LMA LlIA LATA LMA
KO.
SOV
Serial No. 25
Type Sample
1000 1001
24 24
l00.A 100-1 101.1 l0lA 102A 103.A 104.1 l05A 106.1
1002
24
1003 1004
24 24 24 24
1005 1006
1007 1008 1009
24 24
24
24
io00 1001
100.1
100.1 l00A 101.1 l0ld 1OPA 103.1 104A 105.1 106-1
24 24 24
1002 1003 1004
24
1005
24
1006 -. ..
24 -~
1007 1008 1009
24 24 24
245 1
34
34 34 34 34 34 34 i4 34 34 34 34 34 34 34 34 34 34 34 34 -~ 34 34 34
2452 2453 2454 2457 2458 2456 2451 2452 2453 2454 2457 2458 2459 2462 2464 2467 2469 2470 2462 2464 2467 2469
128.4
129.4 129B 130A 1314 131B 132A 134.4 135-1 131.4 131B 132A 134.4
Figure
Run Report Unit 30. To ESSO 1954 API ESSO 1954 rlPI ESSO 1954 API STDOL 1955 LRIA STDOL 1955 LX4 STDOL 1955 L119 STDOL 1955 LMA * Lost sample. ** Irisufficient sample.
Serial
KO, XYZ158 XYZ158 XYZ158 AB123 AB123 -1B123 AB123
,890
ANALYTICAL CHEMISTRY
Lab. Yo. 1954
GR API GR -1PI GR API GR AIPI GR API GR 4 P I GR *1PI GR -%€I' GR API GR API BRO SO BRO S O BRO SO BRO SO BRO SO BRO S O
18000 18001 18002 18003 18004 18005 18006 18007 18008 18009 18000 18001 18002 18003 18004 18005 18006 18007
"0
SO
I3RO so BRO S O BRO SO PT PT PT PT -4sPT A S PT GR API GR A4PI GR API GR .4PI GR API GR API GR 4PI GR API GR API GR API GR API GR API GR API BRO S O BRO NO BRO S O BRO X O
-AS AS AS AS
9.
S o . of Hours of Analyses Work 1
18008
18009
18104 18105 18106 18107 18109 18110 18018 18104 18105 18106 18107 18109 18110 18111 18113 18114 18115 18117 18119 18113 18114 18115 18117
20
30
23 44 44
33 63 63
In
Date Out
Charge SO.
326 326 326 326 326 326 326 326 326 326 326 326 326 326 326 326 326 326 326 326
1234 1234 1234 1234 1234 1234 1234 1234 1234 1234 1234 1234 1234 1234 1234 1234 1234 1234 1234 1234
326 326 326 326 327 327 327 326 326 326 326 327 327 327 328 328 328 328 328 328 328 328 328
2345 2345 2345 2345 2345 2345 2345 2345 2345 2345 2345 2345 2345 2345 2345 2345 2345 2345 2345 2345 2345 2345 2345
Sample inventory
Type
Sample 26 26 26 25 25 25 25
Figure 10.
then sent, attached to the uiipunched master card, to the Tabulating Room. There, the t x o cards are keypunched with the sample description and the proper analysis name and code are added to the marked analysis card. The printed result, verifying the telephone report, is issued with the nest succeeding batch of regular data reports. Other samples of a nonoperating nature but requiring priority treatment niay be handled in a similar manner. T o prerent niisuse of this system, the research director, or an assistant des-
Analysis
A4nalysis GR API VSU 100 YSU 210 N2 CORR SULF D POR PT
Remarks
LST*
Results Sumber Reight 34.8 55.6 44.1
Pass
Void
I?;S**
P.P.11.
Date In Out 328 326 328 326 328 326 326 _ ~ 328 . . ~ 326 328 326 328 326 328
Lab. SO.
18125 18125 18125 18150 _ 18150 18150 18150
Typical report sheet to sample originator
ignated by hini n h o has the sole authority to assign priority, is sent a daily report of the priority samples submitted for analysiq. USE OF PUNCHED CARD SYSTEM I N LABORATORY CONTROL
All the pertinent inforniation concerning the routine activities of the anal!-tical group are readily available for only a small man-hour outlay. This includes a listing of all samples received, the test requested, the uncompleted
analyses on hand. the n-ork that w a ~ : completed on each day, and ~ I i did o it. This inforniation may he sorted in any desired manner and complete printouts made easily. Inventory tabulations are used by the foremen in the individual laboratories. This record is also important to the analytical section head. 1. The size of the backlog indicates lnhoratorirs that are in trouble. Attention should be given to the reason for an cscessive backlog and action taken. n-hich niay include assignment of addi-
tional manpower or decrease in sample input by arrangement with the heads of groups submitting excessive numbers of samples. 2 . -4 ttention to the sample submission dates provides information relative to the effectiveness of the foremen in n ork properly. Khile scheduling yiccial priorities IT ill occur, causing other samples to bp retarded, w r y feiv be allou-ed to become ~ a n i p l ~should s appreciably older than the average backlog age.
Keekly throughput tabulations of all lahoratories, both by research unit and hy analyst, are extremely useful. 1. The output figure for each laboratory gives a direct measure of its efficiency. Consideration of this, along with the output of each analyst, will frequently suggest ways of improving efficiency through better scheduling or reassignment of personnel. 2 . The weekly analytical output, in terms of per cent of total, for each research unit tells directly who is getting what portion of the analytical effort. This information should be availablr to
management to aid in proper research assignments consistent \vith tlie analytical facilities available. CONCLUSIONS
More Effective Laboratory M a n agement. A complete record of in-
put, output, and inventory arranged by unit, laboratory, type of test, or a n y desired classification may be obtained daily, weekly, or monthly. Such tabulations are of great value in scheduling work mithin a laboratory, in assigning manponer nhere i t is needed, and in scheduling pilot plant operation. B substantial increaqe in analytical output has been realized since the business machine system n as put into effect a t Esso Research Laboratories. Reduction in Manpower Assigned t o Data Reporting. Freedoni from
writing report sheets has saved a poition of each analyst's time. I n addition, a reduction of nianpou er assigned t o rerord keeping ha. been achieved.
Increased Speed and Accuracy.
Each answer is reported as it is run and is transcribed only from t h e analyst's work sheet onto the mark sensed card. Availability of Records. Rapid, machine sorting makes i t possible t o locate a n y analysis quickly by a n y type of identification. Summaries of analytical data can be arranged a n d tabulated n i t h ease. ACKNOWLEDGMENT
The authors are indebted to representatives of the International Bu.'m e s s llachine Corp. for assistance in setting up the equipment involved and in training personnel in its use. The folloning items of I B l I eyuipnient have been used in the foregoing operations: 4. 26 Keypunch 5 . 82 Sorter
1. 402 Tabulator '1. 519 Reproducer
6. 77 Collator
3 . 552 Interpreter
RECEIVED for revien. May 26, 1955. Accepted 3Iairh 11, 1958.
Data Plotter RALPH H. MULLER and FRANK D. LONADIER' University o f California, Los Alamos Scientific Laboratory, Los Alamos, The incorporation of a multipoint printout recorder, a sliding translatory potentiometer, and other simple electrical equipment found in the laboratory provides a fast efficient way of plotting data received in tabular form. With simple modification of the electrical circuit, the apparatus will perform other useful functions such as squaring, taking logarithms, square rooting, or plotting hyperbolas. Use of the plotter increased speed from 1.5to 2.5-fold over manually plotting the same points.
T
HE automatic recording of analytically important information is now common practice and is used in spectrophotometers, x-ray spectrometer polarographs, thermogravimetric analysis, and vapor phase chromatography. The converse problem of plotting information If-hich is received in tabular form can become formidable. Elegant machines have been developed for this purpose nhich n-ill accept 5 and y values set in on a keyboard or received from punched-card data. Almost lvithout exception, they are 1 Present address, University of Texas, Austin, Tex.
N. M.
elaborate and costly. They are justified whenever the amount of data to be plotted is large or time is important. The multipoint recording potentionieter, n i t h a few simple accessories, can be used as a data plotter for an occasional job. I n collating a large amount of nuclear data, the authors had repeated occaqion to use these simple arrangements. The immediate discussion is confined to the plotting of y (or a siniple function thereof) against x, m-here tlie increments of s are uniform. I n this special case one depends upon the uniform motion of the recorder chart arid the precise intermittent action of the print nheel t o print the appropriate value of y a t uniform intervals of variable 5 . Any value of y set in by the operator on a voltage divider nill he
followed and duly printed by the recorder. The manner in which the dependent variable is set in by the operator determines the speed and overall coni-enience of the device. I n push-button keyboards, the scientist is likely to be lower in performance than a coniptometer clerk n h o uses the touch system. On previous occasions, a decade resistance box connected in a high resistance sn aniping circuit has been used. If the total resistance of the decade box is several thousand times snialler than the total resistance of the circuit, the potential drop across its qettings nill be subject to negligible errors. A decade box is inferior in speed of operation to a kej board selector, but i t is generally a\railable in a SCALE
1
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I TRANSLPTORY POTENTiOHETER
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Figure 1.
Mechanical arrangement of plotter VOL. 30, NO. 5, MAY 1958
891
