- From: Noah Watkins <nwatkins_at_ittc.ku.edu>
- Date: Thu, 07 Jul 2005 19:48:41 -0500
Well, for anyone wondering, Petter's suggestion was absolutely the right solution. Thanks again. Petter Strandh wrote: >Are you shure the problem isn't electric. Usually there is a protecting >capacitance on the reading channels. What can happen is that you carry >charge between channels when you multiplex. If you short channel 0, what >happens then. > >Unless I misinterpreted you, reading from an unconnected reading channel >has undefined results. It should be connected with something that has a >low impedance as possible. > >Hope that I am not misleading you at this early hour. > >Regards >Petter Strandh > >tor 2005-07-07 klockan 06.37 skrev Noah Watkins: > > >>Hi. >> >>I have a Measurement Computing PCI-DAS6025 board, though the question >>may not be specific to the board. >> >>In the User's Guide provided by the company, a settling time of 25 >>microseconds was typical for reading two different channels >>consecutively and acquiring good data in the worst case. >> >>I am experiencing with the cb_pcidas64 driver a situation where delays >>much longer have to be introduced. For example with nine volts applied >>to channel 8, and nothing applied to channel 0: >> >>Reading from channel 8: ~9V >>Reading from channel 0 to reset >>Sleep for 50 microseconds >>Reading from channel 0: ~7V >> >>In fact, it isn't until i sleep for around 80 _milli_seconds that i get >>readings that are reasonable. Given the sleep time limitation of >>instruction INSN_WAIT, all of my sleeping is occurring at the user >>level. This seems completely unrealistic. >> >>Has anyone ever encountered this degree of settling requirement before? >>Where might be a place to start investigating. >> >>Thanks, >>Noah W >> >>_______________________________________________ >>comedi mailing list >>comedi_at_comedi.org >>https://cvs.comedi.org/cgi-bin/mailman/listinfo/comedi >> >> > > >_______________________________________________ >comedi mailing list >comedi_at_comedi.org >https://cvs.comedi.org/cgi-bin/mailman/listinfo/comedi > >
Received on 2005-07-07Z23:48:41