computers and peripherals without expensive in- ... sample, on the analog data and on the interface ... whereas an analog computer deals with calcula-.
EUROMICRO J O U R N A L 4 (1978) 3|4-317 © EUROM ICROand North-Holland Publishing Company
Microprocessors and instrumentation for chemical pathology A. Musetti Instrumentation Laboratory S.p.A.. Milano. Italy The article contains a brief description clinical chemical analysis over the past microprocessor instruments. A comparison is given. The conclusion projects future essor technology.
of developments in the field of instrumentation for few years. There are sketches of both random logic and of costs of instruments developed by both techniques lines of development of instruments using microproc-
1. INTRODUCTION
drawn by the SAMPLE PROCESSORand introduced i n to the MEASURING CHAMBER. Here the TRANSDUCERS, which are generally optical or electrochemical devices, give out e l e c t r i c a l signals, according to the size of the measurements.
The world of instrumentation for medical analysis has been subject, in many ways~ to an evolut i o n not lacking in controversy as far as performance and optimum number of analyses required by the single instrument is concerned.
These signals are amplified and scaled by the ANALOG PROCESSOR. The ANALOG TO DIGITAL CONVERTER (ADC) transforms the signals so that they can appear on the numerical DISPLAY. These same d i g i tized signals are also sent to the PRINTER INTERFACE which w i l l t r a n s f e r them to the p r i n t e r i t s e l f on command of the LOGIC PROCESSOR.
From elementary apparatus able to carry out one single analysis and process no more than one sample at a time, we have now extremely complex and v e r s a t i l e instruments able to carry our many kinds of analysis on one or more samples both in sequence and simultaneously.
In a d d i t i o n , the p r i n t e r matches samples measured with the i d e n t i f i c a t i o n data by means of a progressive number or code number generated into the autosampler i t s e l f .
The price of such apparatus, the considerable problems involved in maintenance and the small request f o r some of the parameters measured, have l i m i t e d the usefulness of these instruments only to large c l i n i c a l centers.
The input a m p l i f i e r c i r c u i t s and the c a l c u l a t i n g and c a l i b r a t i n g c i r c u i t s are a l l part of the analog processor. However, the name LOGIC PROCESSOR includes a l l the logical c i r c u i t s of the instrument which together form a sequential machine programmed to act on the handling of the sample, on the analog data and on the interface for the p r i n t e r according to the s t i m u l i received from the. external organs connected to i t . The nature of the transducers and the samples used in c l i n i c a l chemical instrumentation requires other c i r c u i t s to be connected to the logic processor.
Today, requests from laboratories and hospitals are mainly d e l t with specialized instruments, able to carry out, as soon as possible, and with the minimum amount of sample, the series of spec i f i c analyses required f o r a p a r t i c u l a r t e s t . Moreover, in order to have easy implementation of both comparisons with c a l i b r a t i o n standards and s t a t i s t i c a l processing as well as q u a l i t y control procedures, the demand f o r automatic handling of measured parameters increases quite a lot.
In f i g . I these c i r c u i t s are indicated as DATA READY and CALIBRATION. By DATA READY we mean a device which indicates when the signals, generated by the transducers, have reached stable value, thus allowing possible t r a n s f e r of the data to the p r i n t e r . The CALIBRATION device, however, is used to compensate the wide signal d r i f t s generated by the transducers.
Microprocessor technology has made easier insert i o n of those features inside the instruments and made also easier instrument connection with computers and peripherals without expensive i n terface boards. 2. RANDOMLOGIC AND MICROPROCESSORPROJECTS
In general t h i s c i r c u i t acts on the scale f a c t o r of a m p l i f i e r s in order to return the signal at the input of the ADC to a constant value when a standard is examined.
Fig. I shows the structure of a t y p i c a l chemical c l i n i c a l analysis apparatus supplied with AUTOSAMPLER and PRINTER, implemented in random l o g i c . The d i g i t a l part of such an instrument is composed of t r a d i t i o n a l T~L or C MOS integrated c i r c u i t s as AND, OR, FLIP FLOP, etc.
As the use of autosamplers becomes ever more frequent, so instruments which carry out automatic c a l i b r a t i o n , the moment the LOGIC PROCESSOR is aware of i n t r o d u c t i o n of a standard i n t o the measuring chamber, become more diffused.
The physical process can be summarized as f o l lows: the samples placed in the AUTOSAMPLERare 314
Chemical Pathology
7
ANALOG I PROCESSOR
ITRANSDUCERi
1
I MEASURINGI CHAMBER I
-II
READY
I SAMPLE PROCESSOR
I
CALIBRATION
IT
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315
11 LOGIC
-I
PROCESSOR
'-
PRINTER I
INTERFACEI
J I PRINTER I
II
I EXT--L i,o I Fig. 1. Fig. 2 i s a s k e t c h o f t h e t y p e o f instrument which could be implemented using a microprocessor.
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The electronics which was part of the SAMPLE PROCESSOR is included in the software leaving in this way only the electromechanical organs concerned with the treatment of the sample, reagents and of the washing liquids.
The differences between this and the previous schematic are to be found mainly in the part dealing with analog processing made by SAMPLE PROCESSOR. The analog processor is replaced by an input amplifier followed immediately by the digital-to-analog converter. Once the measured voltage has been digitized by the chain ANALOG AMPLIFIER-ADC, the whole data and sampleprocess: calculations, automatic calibration, autosampler controls, etc. - occurs inside of the microprocessor.
ITRANSDUCER~--~ I MEASURING CHAMBER I
1
3. ECONOMICCOMPARISON BETWEEN RANDOMLOGIC AND MICROPROCESSORS 3.1. A practical example The project of an inst~ment in random logic such as the one described above is developed on 8-10 printed c i r c u i t boards with more than one
~
ANALOG AMPLIFIER - ~
ADC
11 MICRO PROCESSOR
I SAMPLE L
--!
DISPLAY
---I
PROCESSORU
PRINTER EXTERNAL I
Fig. 2.
I/o
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A. Musetti
hundred d i g i t a l and analog integrated c i r c u i t s . The same s t r u c t u r e , using the microprocessor technique, means a reduction in the number of printed c i r c u i t s to 4-5 and generally only one of them is dedicated to the analog part. Let us take as example, the IL 613 Blood Gas Analyser made by Instrumentation Laboratory. This instrument measures pH and p a r t i a l oxygen and carbon dioxide pressures simultaneously from 300 ~I samples of blood. The instrument is equipped with automatism f o r the i n t r o d u c t i o n i n t o the measuring chamber of sample, standard and cleaning s o l u t i o n . In addition i t is supplied with automatic c a l i b r a t i o n on the three channels, whereas an analog computer deals with calculat i o n of four parameters derived from those measured. Also part of the instrument is a p r i n t e r capable of supplying in s u i t a b l e format a complete set of both measured and calculated data. Between the e l e c t r o n i c parts of the random l o g i c presently in production and the microprocessor version under study, there exists a difference of standard cost of approx. 30 % to the advantage of the microprocessor project. In f a c t the random l o g i c instrument is composed of 9 boards and the price for the components alone is of approx. L i t . 750,000. The microprocessor i n s t r u ment w i l l be composed of only 4 printed c i r c u i t s of the same size as those of the random l o g i c , bringing the cost to L i t . 500,000 approx. In the random l o g i c project the necessary use of expensive analogic components such as F.E.T., precision r e s i s t o r s and capacitors mean that the d i g i t a l part is involved only by 30 % in the entire electronics. In a microprocessor instrument the analog part is reduced to a single printed c i r c u i t board containing the high impedence c i r c u i t s necessary to the transducers and w i l l involve 30 % of the t o t a l cost of the components. The other three cards containing the equivalent e l e c t r o n i c of l o g i c processor represent the remaining 70 %. I f to the amount already indicated we add the cost of a p r i n t e r , a f u r t h e r increase of approx. L i t . 600,000 must be considered for the random l o g i c instrument. The use of microprocessors means the same performance but with much less sophisticated p r i n t ers. By reducing hardware and increasing s o f t ware a saving of 35 to 45 % is obtained. 3.2. Future developments Looking ahead at f u t u r e developments, i t must be considered that the microprocessors and the large scale i n t e g r a t i o n c i r c u i t s associated with them as support and i n t e r f a c e , are oriented to a reduction in p r i c e , whereas the integrated c i r c u i t s in TTL or in C MOS already have established prices on the market. In addition to the immediate economical advantages, on a productive basis, the microprocessor logic permits a progressive reduction in the
1st BOARD
2nd BOARD
3rd BOARD
4th BOARD
Fig. 3. cost of research and development with every new project. A f t e r the f i r s t substantial expense necessary for apparatus and the t r a i n i n g of personnel, i t is possible to u t i l i z e much of the previous studies already made on both software and hardware. Some operations such as a u t o c a l i b r a t i o n , data ready, i n t e r f a c i n g with p r i n t e r , f i n d t h e i r place in almost every instrument. Let us examine the schematic of f i g . 3, where we can see the t y p i c a l microprocessor l o g i c for an instrument f o r medical analysis. The hardware c o n f i g u r a t i o n of the f i r s t three cards can be generalized and used in many instruments changing only the contents of the memories. The fourth card: general purpose interface - must however be redesigned f o r every new instrument. A standard structure is therefore obtained with considerable advantages in production, t e s t i n g and maintenance. However, operators of instruments for medical analysis must not expect to see a drastic reduction in the cost of the instruments with the introduction of microprocessors. To begin with, a 20-30 % saving on the electronic part alone means a 7-10 % reduction in the cost of materials on the inside of the entire instrument. The mechanical and f l u i d i c parts regarding the treatment of the sample and mea2 of suring cell in fact generally account for T the entire cost. Another advantage of microprocessors is that i t
Chemical Pathology is extremely easy to introduce other performances, such as: -autodiagnostic c i r c u i t s , q u a l i t y control r o u t i n e s , i n c r e a s i n g l y more s o p h i s t i c a t ed and e f f i c i e n t automatisms for the treatment of the sample and data. The i n s e r t i o n of these performances could increase the necessity of memory and complicate the i n t e r f a c e with SAMPLE PROCESSOR in such a way as to compensate the economic advantages obtainable with respect to the random l o g i c . 4. INTERFACINGWITH COMPUTERSAND PERIPHERALS A b r i e f mention regarding interfacement between c l i n i c a l chemical analysis instruments and computers has to be discussed. Above a l l in t h i s case the microprocessor technique has s i m p l i f i e d the i n t e r f a c e c i r c u i t s a l lowing d i r e c t contact between the microprocessor bus and that of the computer by means of simple integrated modules. In t h i s way we avoid the complicated devices for the t r a n s f e r of the signals from c i r c u i t s in random l o g i c on the inside of the computer i t self. Most modern apparatus is equipped with video, floppy disk and other terminals as input and output devices which, being operated by the microprocessor i t s e l f , allow a more immediate communication between the operator and the i n strument, plus a clearer display of the a n a l y t i c results. Even the ever i n c r e a s i n g l y f e l t problems of automatic sample i d e n t i f i c a t i o n finds a simpler s o l u t i o n with the use of microprocessors as reading organs and control of the i d e n t i f i c a t i o n codes. The c o n f i g u r a t i o n can be decided on by the operators themselves according to the requirements of t h e i r p a r t i c u l a r laboratory, i n terconnecting in t h i s way a whole series of single " i n t e l l i g e n t " instruments which can communicate with a central computer and control u n i t responsible for the synchronization of times, the control and v e r i f i c a t i o n of the data by introducing standard samples plus the p r i n t i n g of the parameters on a single piece of paper r e f e r r i n g to the same sample. Research instruments more than specialized i n struments w i l l benefit by the i n t r o d u c t i o n of microprocessors thanks to the increased possib i l i t y of handling the data on the inside of the instrument and the a v a i l a b i l i t y of a programming console which allows the arrangement of the measurement cycles as desired and in such a way that they can be carried out automatically and in repeatable sequence. We conclude that the i n t r o d u c t i o n of microprocessors in instrumentation for c l i n i c a l chemical analysis offers considerable advantages not only where automation of the single instrument is concerned, but also where an e n t i r e analysis laboratory is involved. This means a reduction in operation costs, more
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r e l i a b l e analysis and rapid expansion of laboratory capacities with d i r e c t i n t r o d u c t i o n of new instruments "on l i n e " in already e x i s t i n g chains. Because the processor section of most i n s t r u ments represents only a portion of the small costs and because the new instruments w i l l have increased c a p a b i l i t i e s , t h e i r cost w i l l probably not be reduced s i g n i f i c a n t l y .
