The Scientific Department of the National Gallery



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Computing

The recent phenomenal progress in computing facilities has been reflected on a small scale in the Department's change from hand-operated calculator in the '50s through electromechanical and programmable desk-calculator to the present Wang system with 16K capacity (Fig.12).


Top-of-the-range calculators such as the Wang overlap the minicomputer in price and capacity, the minicomputer having advantages in speed of operation for long routine calculations and in link-up with instruments, and the Wang in mathematical work and ease of programming.
The system in use at present comprises a 16K central processing unit with CRT display, storage on disc and magnetic-tape cassette, a punched-tape reader and an IBM plotter/writer for hard copy. Its instructions are in Basic. Its ease of programming, with sixteen lines of programme or output displayed on the screen at one time, has made it possible for the staff of the laboratory to write their own programmes without the need to attend any training course.
Some of the uses made of the Wang system are as follows:
Each week the punched-tape output voltages from the data logger are read, converted to illuminance, relative humidity and temperature and printed out as a table. A programme for drawing attention to malfunctions is also used, and the data can, of course, be manipulated as required.
Colour-rendering calculations of fluorescent lamps and other illuminants, which took half a day with the electromechanical calculator, can now be carried out in five minutes. Formerly the time needed to acquire such information was often not available.
The Wright-Wassail spectrophotometer being a single-beam instrument, each wavelength reading must be referred to an internal standard, which in turn is referred to a ceramic-tile standard. In practice groups of readings are outputted to punched tape. Averaging and all subsequent computations of reflectance readings are carried out by the Wang.
The Wang is also used to integrate gas-chromatograph peaks for quantitative work. When fed with retention times from capillary-column gas chromato- graphs it will deal with variations caused by column ageing and identify peaks from a store of data on known compounds.
Lastly we are starting to put chemical data and other reference material onto magnetic tape, but find inevitably that we shall have to increase our storage capacity.
Several other programmes have been developed for use in current research, but the reader will note that two items in the above list depend on the Wang. The data logger has the great advantage that it can accept voltages from any type of sensor, but its punched-tape output can only be machine-read, and the Wright-Wassail spectrophotometer would be a very slow instrument without computing backup.




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