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Virtual Spectrometer Overview

Virtual Spectrometer Overview


Overview of the Virtual Spectrometer

The Virtual Spectrometer module in NUTS consists of a set of commands which simulate an FT-NMR spectrometer, producing realistic data corresponding to acquisition parameters set by the user. It is designed to mimic a "vanilla" NMR spectrometer, rather than imitating any actual manufacturer’s instrument. In addition to the functions which are specific to the Virtual Spectrometer, all of the processing capabilities of NUTS are also available. Commands specific to the Virtual Spectrometer are available from the vSpec menu.

As with the rest of the NUTS program, most commands can be executed either from the menu or as keyboard commands,  which are 2-letter commands executed without typing <Enter>.

The virtual NMR "sample" is a text file containing some parameters and a list of NMR frequencies and their intensities. Several sample files are provided (as a zip file for Windows and .sea file for Mac), and an example can be viewed which includes an explanation of the different items in these files. The file must contain certain keywords which allow the Virtual Spectrometer to interpret correctly the data being read from the file. The file is most easily created from within the NUTS NMR simulation subroutine, but can also be created from scratch or edited using any text editor.

The user must set values for several NMR acquisition parameters as well as select the sample whose spectrum will be acquired. The sample is chosen using the GS command or by selecting Get Sample from the vSpec menu. This opens a standard dialog box for specifying the name of a file to be opened. The file itself is not opened or shown at this time; this is simply the process used to retrieve the name of the file which will be read when acquisition is started. To set acquisition parameters, type VP or select Parameters from the vSpec menu. This opens a dialog box for input of parameters.

Once parameters are entered, the dialog box is closed and data acquisition initiated by typing ZG or selecting Zero and Go from the vSpec menu. Messages are displayed on the screen as acquisition proceeds, and the accumulating FID is displayed. If the user’s PC is equipped for sound, the FID will be "played" through the PC’s speakers (Windows only). Upon completion of data acquisition, the data can be processed using the NUTS processing capabilities.

A Tutorial is available as a Word document, and illustrates use of the Virtual Spectrometer.

Commands for the Virtual Spectrometer

GS    Get Sample. Specifies the file from which frequencies will be read.
ZG    Zero & GO. Reads the file containing freqencies and generates the NMR data.
VP    Virtual Parameters. Opens a dialog box to set acquisition parameters.

Virtual Spectrometer Parameters

Acquisition parameters are input using the dialog box shown below, which is activated by typing VP or by selecting Parameters from the vSpec menu. A brief explanation of each item is shown below.

http://www.acornnmr.com/content/uploads/vp.gif (24428 bytes)

User:    Enter user’s name or initials (for information only; does not affect data acquisition)
Date:    for information only; does not affect data acquisition
Experiment:    Select from the list of available experiments. Currently the only option is Single Pulse.
Scans to do:    Enter the number of scans (acquisitions) which will be collected and added to form the final spectrum.
Pulse Width:    The excitation pulse width in microseconds.
Recycle Delay:    Delay between repeat scans to allow relaxation, in sec.
Receiver Gain:    Adjusts the amplitude of the signal going into the receiver.
Spectral Width:     Frequency range for the spectrum.
Spectrum Offset:     Frequency of the "carrier", or center of the spectrum.
Data Size:         Number of data points to be acquired.
Delay for first point:     In microseconds.

The following values are displayed for information only, and cannot be changed directly.

Acquisition Time:    The time required to complete a single scan, dependent on the Spectral Width and Data Size.
Digital Resolution:     The number of data points per Hertz which will define the final spectrum.
Dwell Time:    The time between data points, in microseconds. This is determined by the value chosen for Spectral Width.

Descriptions are available explaining how the setting of each parameter will affect the spectrum.

Last updated 3/20/99.