- From: Ray Kelm <rhk_at_newimage.com>
- Date: Fri, 09 Aug 2002 12:25:13 -0400
Calin A. Culianu wrote: > On Thu, 8 Aug 2002, Frank Mori Hess wrote: > > >>>However, if I disable channel 1 in software, the interference pattern >>>disappears. >>> >>>***Even though channel 1 is still physically connected to its signal >>>source**. >>> >>>Basically, the simple act of issuing a comedi_data_read() on channel 1 >>>affects/modifies the waveform I get out of channel 2. >>> >>>Is this odd or what? >> >>It is how the software is currently designed to work. > > > Hmm. Frank.. while I respect your tremendous prowess as a programmer and > designer, and consider you tremendously gifted in all matters of the > cb_*.c files, I want to ask you if it's possible to reconsider this design > (is it possible from a technical standpoint to change the driver file to > remove unwanted channel noise).... ? > > This behavior isn't exhibited with other drivers for other boards > (ni_pcimio, for one, doesn't have strange interactions between channels). > What's more, when using this board for things like scientific experiments, > the level of 'noise' you get due to the interactions between channels for > this card is unacceptable. We had to discard megabytes upon megabytes of > heart ECG data from one of our pig experiments because the ECG from the > pig's heart was unacceptably noisy. The pig died, Frank!! How many more > pigs must die before we can finally rid the world of heart disease? > What's more, how many more pigs must die senselessly due to noisy data? > Go back and look at the specs for your board. You can only get fast readings if you don't switch channels. The multiplexers on that series of boards seem to be really slow. That is the exact reason I switched my systems from those boards to the NI boards. -Ray
Received on 2002-08-09Z15:25:13