S.P.E.C.T.R.U.M.

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S.P.E.C.T.R.U.M.: Freeware signal processing program for Macintosh

Many of the figures in this paper are screen images from S.P.E.C.T.R.U.M. (Signal Processing for Experimental Chemistry Teaching and Research/ University of Maryland), a Macintosh program we have developed for teaching signal processing to chemistry students.

Click to enlarge

SPECTRUM is designed for post-run (rather than real-time) processing of "spectral" or time- series data (y values at equally-spaced x intervals), such as spectra, chromatograms, electrochemical signals, etc. The program enhances the information content of instrument signals, for example by reducing noise, improving resolution, compensating for instrumental artifacts, testing hypotheses, and decomposing a complex signal into its component parts.

SPECTRUM was the winner of two EDUCOM/NCRIPTAL national software awards in 1990, for Best Chemistry software and for Best Design.

Features

Reads one- or two- column (y-only or x-y) text data tables with either tab or space separators.
Displays fast, labeled plots in standard resizable windows with full x- and y-axis scale expansion and a mouse- controlled measurement cursor.
Addition, subtraction, multiplication, and division of two signals.
Two kinds of smoothing.
Three kinds of differentiation.
Integration.
Resolution enhancement.
Interpolation
Fused peak area measurement by perpendicular drop or tangent skim methods, with mouse-controlled setting of start and stop points.
Fourier transformation
Power spectra
Fourier filtering
Convolution and deconvolution
Cross- and auto-correlation
Built-in signal simulator with Gaussian and Lorentzian bands, sine wave and normally-distributed random noise.
A host of other useful functions, including: inspect and edit points, normalize, histogram, interpolate, zero fill, group points by 2s, bridge segment, superimpose, extract subset of points, concatenate, reverse X-axis, rotate, set X axis values, reciprocal, log, ln, antilog, antiln, standard deviation, absolute value, square root.

SPECTRUM can be used both as a research tool and as an instructional aid in teaching signal processing techniques. The program and its associated tutorial was originally developed for students of analytical chemistry, but the program could be used in any field in which instrumental measurements are used: e.g. chemistry, biochemistry, physics, engineering, medical research, clinical psychology, biology, environmental and earth sciences, agricultural sciences, or materials testing.

Machine Requirements: Any Macintosh model with minimum 1 MByte RAM, any standard printer. Color screen desirable. SPECTRUM has been tested on most Macintosh models and on all versions of the operating system through OS 8.1.

PC users can run SPECTRUM via a Macintosh emuator. Currently available Macintosh emulators include the Ardi Executor (http://www.ardi.com/executor.php), SoftMac (http://www.emulators.com/download.htm), Basilisk II (http://basilisk2.cjb.net/), Basilisk II JIT (http://gwenole.beauchesne.online.fr/basilisk2/), and vMac (http://www.vmac.org/).

The full version of SPECTRUM 1.1 is now available as freeware, and can be downloaded from http://www.wam.umd.edu/~toh/spectrum/. There are two versions:

SPECTRUM 1.1e: Signals are stored internally as extended-precision real variables and there is a limit of 1024 points per signal. This version performs all its calculations in extended precision and thus has the best dynamic range and the smallest numeric round-off errors. The download address of this version in HQX format is http://www.wam.umd.edu/~toh/spectrum/SPECTRUM11e.hqx.

SPECTRUM 1.1b: Signals are stored internally as single-precision real variables and there is a limit of 4000 points per signal. This version is less precise in its calculations (has more numerical round-off error) than the other version, but allows signals with data more points. The download address of this version in HQX format is http://www.wam.umd.edu/~toh/spectrum/SPECTRUM11b.hqx.

The two versions are otherwise identical.

There is also a documentation package (located at http://www.wam.umd.edu/~toh/spectrum/SPECTRUMdemo.hqx) consisting of:

1. Reference manual. Macwrite format (Can be opened from within MacWrite, Microsoft Word, ClarisWorks, WriteNow, and most other full-featured Macintosh word processors). Explains each menu selection and describes the algorithms and mathematical formulae for each operation. The SPECTRUM Reference Manual is also available separately in PDF format at http://www.wam.umd.edu/~toh/spectrum/SPECTRUMReferenceManual.pdf.

2. Signal processing tutorial. Macwrite format (Can be opened from within MacWrite, Microsoft Word, ClarisWorks, WriteNow, and most other full-featured Macintosh word processors). Self-guided tutorial on the applications of signal processing in analytical chemistry. This tutorial is also available on the Web at (http://www.wam.umd.edu/~toh/Chem498C/SignalProcessing.html)

3. Tutorial signals: A library of pre-recorded data files for use with the signal processing tutorial. These are plain decimal ascii (tab-delimited) data files.

These files are binhex encoded: use Stuffit Expander to decode and decompress as usual. If you are downloading on a Macintosh, all this should happen completely automatically. If you are downloading on a Windows PC, shift-click on the download links above to begin the download. If you are using the ARDI Executor Mac simulator, download the "HQX" files to your C drive, launch Executor, then open the downloaded HQX files with Stuffit Expander, which is pre-loaded into the Executor Macintosh environment. Stuffit Expander will automatically decode and decompress the downloaded files. Note: Because it was developed for academic teaching application where the most modern and powerful models of computers may not be available, SPECTRUM was designed to be "lean and mean" - that is, it has a simple Macintosh-type user interface and very small memory and disk space requirements. It will work quite well on Macintosh models as old as the Macintosh II, and will even run on older monochrome models (with some cramping of screen space). It does not require a math co-processor.

T. C. O'Haver
Professor Emeritus
Dept. of Chemistry and Biochemistry
University of Maryland
College Park, MD 20742
toh@umd.edu
http://www.wam.umd.edu/~toh/

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This page is maintained by Prof. Tom O'Haver , Department of Chemistry and Biochemistry, The University of Maryland at College Park. Comments, suggestions and questions should be directed to Prof. O'Haver at toh@umd.edu.

Last updated September 2006.