Acquisition parameters

This window shows a summary of the data acquisition parameters for each channel (the physical A to D input, the A, B, and C (exponent if power function) values for voltage conversion, the Y-axis scaling, the number of readings averaged, and the channel label).  To alter any of these parameters, click the cursor in the appropriate edit field and change the parameter as desired.  This example for Chart mode shows ten input channels:

  • In Oscilloscope and Oscilloscope plus Chart mode, some edit fields are 'fixed' and cannot be changed.  These have a dark gray background. 
  • A channel used for the keyboard event recorder must have an A value of -9999.  The B and C values are not used. 
  • The A, B, and C values for a 3-order polynomial are replaced by a button, as seen here for channel 10.  Click this to change polynomial variables. 

  •   In Chart mode, the default averaging mode is continuous repeated readings until the time of the next sample ("Continuous averaging" mode), and the 'number averaged' fields read 'scan'.


    NOTE: If you load a setup file that was (a) made for a different A-D converter than the one in use, and (b) one or more of the hardware A-D input assignments in the setup file are outside of the range of A-D inputs on the current A-D converter (for example, the A-D converter you are using has 12 inputs and some of the assignments are for inputs 13, 14, 15, or 16), the following window appears:

    Either delete the offending channels, or change their A-D inputs to values within the scope of the A-D converter in use.  If you don't, there is an excellent chance the program will 'lock up' (freeze) when it tries to read data from nonexistent hardware.

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  •   The CONVERSIONS menu lets you use the regular voltage Conversions window to adjust the voltage conversion parameters on each channel (except for oscilloscope channels, which read raw input voltage only).  You can also access the set alarms window to configure an appropriate alarm setup (see the MENU section for details).

  •   To test the voltage conversion and display parameters for any channel, click the appropriate "Ch.  #" button in the leftmost column.  A window will open showing a scrolling display of the current input values on the selected channel:

    This will allow you to adjust any voltage offsets, gains, etc. before starting a data acquisition run. You can switch between fast and slow updating by pushing the 'update' buttons (slow updating is sometimes more readable), and you can adjust the number of averaged samples per update with the 'average' buttons.

    In this example, sampling began at a low averaging number (1) and then the user raised the averaging number to 20 -- resulting in a much 'smoother' plot.

    CAUTION:   With slow A-D converters, such as the ADAM units, some DataTakers (DT50, 500, or 600), or ADC-1s, response to button clicks may be delayed and the update rate may be very slow if you select a high averaging number.

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  •    In Chart mode, Scope plus Chart mode, or Multichannel Oscilloscope mode, you can add or delete channels with buttons in the lower left corner.  This example shows three channels being removed from a 9-channel setup:

    You cannot add beyond 16 channels in Chart mode (5 in Scope plus Chart mode), and (obviously) you cannot cut to less than 1 channel in Chart mode (2 in Scope plus Chart mode).

  •    You may also change the sample interval (both the oscilloscope and chart channel intervals can be changed if you are in Oscilloscope plus Chart mode), the control of external devices, set up triggering, or restart LabHelper (this is useful if you want to load a setup file, or change the recording mode).

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  •   The 'Chart View...' button opens a window that allows selection of the 'density' of data plotted in chart mode:

    The normal view contains one sample per pixel on the x-axis.  However, you can select compression ratios of 2, 2.5, 4, 5, and 10 (these options are available only if the number of chart samples is greater than the number of samples per screen).  Thus with a 640-pixel-wide screen, up to 6400 samples can be shown on a single screen.  The range is 832 - 8320 when using an 832 pixel-wide screen, and so forth with larger screen sizes.

    Using the more compressed views increases the amount of recording time that fits on the screen, but at the same time the screen resolution is decreased (for viewing only; not recording) because several samples are plotted within the same x-axis pixel position.

    Some combinations of view compression and maximum sample number may generate fractional time units on the X-axis of the chart display.  However, you can manually adjust the scaling of the 'time tics' on the x-axis (if they are used) with the 'custom tic unit' button.

    If the number of samples is greater than can be shown on a single screen, the chart display must be scrolled when the data plot reaches the screen's right edge.  The default scrolling value is 100% -- that is, the entire screen is redrawn, showing none of the previously-acquired data.  Alternately you may select fractional scrolling (50%, 67%, or 75%), which leaves some of the previously-acquired data in view.

  •   The 'Scope View...' button opens a window that allows selection of the 'density' of data plotted in scope mode.  It is similar to Chart View, except that it offers options to show only a fraction of the gathered data (all will be saved if a file is stored).  This can increase the display rate and hence the fraction of total time spent in sampling data (however, it's of little use with slow A-D converters).

    Note that you should use the "show every point" option UNLESS you don't need to see every display point:

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  •    The 'Screen View...' button lets you divide the screen up among the different channels according to your own preferences.  For example, you can show some channels in large vertical scale and others in much smaller scale.  Note that because there is a fixed amount of screen space available, making a channel larger than normal requires shrinkage of other channels:

    To set channel heights, move the cursor within the simulated plot area until it is at the desired height, then click.  The program steps through the channels in sequence.  When all channels are complete, you can accept the results, use normal values (all channels with equal heights), or redo the selection.  The program always reserves a minimum amount of space for any remaining channels (20 pixels high).  Channel heights do not affect other aspects of the data acquisition process.

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    At the bottom of the Acquisition parameters screen are buttons to select:

  •   The maximum number of samples to be gathered in chart mode before LabHelper stops to save the recorded information.  The value can be incremented in units of screenwidth pixels up to the maximum of two million.  These buttons are not available in Oscilloscope mode.

  •    The number of samples in a scope screen (in Oscilloscope or Oscilloscope plus Chart mode).  The choices are 640 up to 65,500 (depending on the size of the screen).  The value can be incremented in units of 640, 832, etc.  depending on screen width.  These buttons are not available in Chart mode.

  •   Whether or not the computer beeps at each sample (not available in Oscilloscope mode, or at high sampling rates in other modes).

  •   The AUTOREPEAT option.  Autorepeat (Chart mode only) instructs LabHelper to automatically save data when the maximum number of samples has been recorded, and then automatically restart acquisition.  If this option is selected, a standard Mac file opening dialog will appear, requesting a file root name.  Saved files will have a name consisting of the root (e.g., 'bird data') plus a suffix corresponding to the sequence number (e.g., 'bird data 1', then 'bird data 2', then 'bird data 3', etc.).

     WARNING:  if you selected a large number of samples, be sure you have plenty of disk space available to save the expected number of files!

    After the file root is selected, LabHelper presents a window for entering a comment string and data for gas exchange calculations (body mass, flow rate, barometric pressure, etc.).

    If you are in Oscilloscope plus Chart mode, a button for Automatic markers is displayed at the bottom left of the screen.  If this button is ON, LabHelper will insert a marker into the chart files whenever an oscilloscope screen is saved.  These markers are a sequence of numbers from 0 to 9, which repeats up to a total of several thousand markers.  You can also enter markers manually by pushing any letter or number key.

  •    Edit these values as necessary and click the 'Setup OK' button.


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