Re: [rtl] AD-card

[David Schleef <ds@stm.lbl.gov>]

On Tue, Aug 01, 2000 at 01:40:09PM +0200, Peter T. Drechsler wrote:
> Hi.
> 
> Can anyone recommend me a decent AD-Card that runs under RTLinux.
> Kernel is 2.0.33 with appropriate RT-Patch. Runs. 
> Could be PCI ot At.
> Should have at least 8 analog inputs with gains (12 Bit is ok). 
> Should have 2 or more analog outputs, preferable 0-10V.

Look at Comedi.  http://stm.lbl.gov/comedi.  Lots of boards
supported.


> I want read out thermoelements type K. Since the voltages are micro-V
> I need gains in the order of 10, 100, 1000. 


Are you sure that you need real-time?  Thermocouple leads make great
antennas, and because of this are usually heavily filtered, sometimes
using a 1 Hz low pass filter.  The latency in the filter usually
is greater than the latency of Linux.  (This may be irrelevant if
you have another need for real-time.)

Also, it is usually recommended to use external amplification and
filtering for thermocouple inputs.  (And from personal experience:
if possible, find a circuit that can detect disconnected
thermocouples...)



dave...