Re: Unipolar X Bipolar X single-ended X diferential

On 22/06/07 14:45, Paulo André Capellari wrote:
> I'm wondering about the following: in a daq-board, the Unipolar/Bipolar
> function determines the arrangement (single-ended / diferential) of the
> circuit or not?  Can I do the acquisition in a configuration like this:
> Bipolar in single-ended mode in the pcm-3718, for example??? (the board
> isn't the problem, the configuration is....)

As far as I can tell from the pcl818.c driver source, you can't choose
the single-ended / differential arrangement programmatically.  I think
it must be set by a jumper or something.  The driver reads the card
status during comedi_config to determine which mode it is in.

Unipolar / bipolar are just different types of voltage ranges.

You can specify the analog reference and the voltage range in the
channel list by using the CR_PACK(chan,rng,aref) macro to construct the
channel list entry.  The analog reference would be AREF_DIFF for
differential mode, and probably AREF_GROUND or AREF_COMMON for
single-ended mode.  But the pcl818.c driver ignores the analog reference
specified here.

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-=( Ian Abbott _at_ MEV Ltd.    E-mail: <abbotti_at_mev.co.uk>        )=-
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Received on 2007-06-27Z10:36:51