Recording modes and channels

Before LabHelper can acquire data, it must be given a sampling protocol which includes the following (some of these are optional):

  • recording mode
  • sample rates
  • matching logical to hardware channels
  • digital control of external devices
  • audible timer
  • alarm settings
  • the number of input channels
  • signal processing and voltage conversion
  • the duration of sampling
  • screen appearance options
  • analog output and feedback settings
  • X-Y plotting

    • The initial input controls of LabHelper are be shown as a set of tabbed windows (below).   You need to select one of three modes of operation:

    • Chart
    • Oscilloscope
    • Oscilloscope plus chart

    You can also load a 'setup file' with a complete pre-recorded sampling protocol (setup files are stored from the OPTIONS window).   This will take you directly to the Acquisition parameters window.

  •   CHART MODE gathers a fixed amount of data from 1 to 16 channels (up to two million cases); the operator can intervene at any time to stop acquisition before the maximum number of samples is obtained.  Data are plotted as separate line graphs for each channel.  Data are stored either under manual supervision (i.e., the operator selects a new file name for each set of data) or automatically under the autorepeat option.  In autorepeat mode, the operator provides a 'root' file name before data acquisition starts.  Subsequently the program automatically saves data whenever its buffer is full, appending sequential suffixes (1, 2, 3, 4, etc.) to the file root name for each save.  Sample rates for single channels can be as fast as several hundred per sec if you have a fast CPU and A-D converter, but are slower if the number of channels is large.

    • The maximum 1-channel sampling rate is 3-5 samples/second with a slow DataTaker (DT50/500/600, about 10/second with ADAM modules, 20-50/second with a DataTaker DT800 (high-speed mode), > 200/second with a Sable UI2, and 62/second with a Sable UI3 (it should go faster but that's the maximum at this time).

  •   OSCILLOSCOPE MODE works like a typical oscilloscope.  Data from a single channel are plotted from left to right.  Whenever the next point would 'fall off' the right edge of the screen, plot position is swapped to the left edge and each new point 'erases' the previous point at that x-coordinate.  The operator provides a 'root' file name before data acquisition starts.  Whenever the TAB key is struck, the existing screenfull of data is saved under the root name plus a sequential suffix number (see detailed description in the SETTING UP section).  An oscilloscope screen can contain up to 65,500 samples (about 16,000 samples in some sampling conditions).

    • If you are using a slow DataTaker (DT50/500/600), the maximum sampling rate is quite low, so oscilloscope mode is NOT available.
    • With the faster DataTaker DT800, modest scope sampling rates are possible but see this page to understand the limitations.

  •   OSCILLOSCOPE PLUS CHART MODE combines an oscilloscope channel with one to four chart channels.  Sampling rates for oscilloscope and chart channels are usually quite different.  Because this mode is a combination, it is also a compromise:  The oscilloscope channel cannot sample as fast as in 'pure' oscilloscope mode, sample averaging is keyed to the sample rate of the oscilloscope channel, and autorepeat is not available.  You should also be aware that if the chart channel sample rate is high, chart timing may be affected by the time lost when oscilloscope screens are saved to disk.

    • If you are using a slow DataTaker (DT50/500/600), the maximum sampling rate is quite low, so oscilloscope plus chart mode is NOT available.
    • With the faster DataTaker DT800, modest scope sampling rates are possible but see this page to understand the limitations.
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