Channel Selection and Settings
After the sample rate is chosen in Chart mode or Oscilloscope plus Cart mode (but not in Multichannel Oscilloscope mode), the program 'loops', one channel at a time, through a series of windows that define the ACQUISITION PARAMETERS specific to each channel.  The red panel at the top of the screen indicates which channel is being defined at the moment.  For each channel, you must select the following:

A to D INPUT This lets you match the 'logical' channel to an actual physical connector to the analog-to-digital converter (National Instruments board, ADC-1, etc.).  You can select any of the A to D channels that are available, in any order; you may also assign a single hardware input to several logical channels.

• Note:  When using the ADC-1, you can set each channel to automatically adjust the gain function to maximize resolution (the default mode), or to use a fixed gain (of 1 or 50).  The latter option is slightly faster. 

The A to D INPUT window looks like this (approximately; the number of available inputs depends on the particular A to D converter in use):

Here, sixteen inputs are available. One (# 1) has already been selected, and the user has chosen input 7 for channel 2. 

   DISPLAY SCALING     This sets the Y-axis scaling for the computer's stripchart or oscilloscope display.

   SAMPLE AVERAGING     This sets the method and number of samples to be averaged for each recorded data point.

Once all these values have been defined for the various channels, the acquisition parameters can be saved in a 'setup' file for later use.  This enables you to use the same sampling parameters without having to redefine them every time the program is run.  Setup files are saved from the OPTIONS window.

In Multichannel Oscilloscope mode, the characteristics of the A-D hardware determine the gain and A-D input selection options for each channel.  The major points are:

• All channels sample at the same rate (however, the available sample rates vary slightly, depending on the number of channels)
• All channels must have the same gain and range. 
• The physical hardware A-D input is the same as the channel number -- in other words, if you are sampling 4 channels, you must use the first 4 physical connectors.  Logical channel one is matched to A-D input 1, logical channel 2 to A-D input 2, and so on.  This is fundamentally different from the other modes, where any physical A-D input can be assigned to any logical channel. 

go back to the LabHelper Topics page

go to the Warthog Systems page

go to Mark Chappell's page