[prev in list] [next in list] [prev in thread] [next in thread] 

List:       comedi
Subject:    quadrature measurement noise
From:       Everett Wang <everteq () sbcglobal ! net>
Date:       2006-09-05 17:14:58
Message-ID: 20060905171458.21380.qmail () web81515 ! mail ! mud ! yahoo ! com
[Download RAW message or body]

Hi All,
   
  I have a strange problem using quadrature in comedi: not so random noise. The \
measure at a constant rotation rate is almost a straight line. When taken a \
difference between two consecutive points for speed, it exhibits some error for less \
than 1% of the points. For these points the velocity can vary up to 20% of speed \
value, while the rest of the points are well on target.  
  I am using a US digital encoder 512 pulse per rotation. I also tried a totally \
different encoder with similar result. The axis rotation rate is 700 rpm. The board \
is a Sensoray 526 PC104. Software is Linux 2.6.17, RTAI 3.4 test1 and comedi-0.7.73 \
and comedilib-0.7.72.   
  Any suggestions are welcome, :-D
   
  Everett
   
   


[Attachment #3 (text/html)]

<div><BR>&nbsp;</div>  <div><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Hi \
All,<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" \
/><o:p></o:p></SPAN></div>  <div><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: \
Arial">&nbsp;<o:p></o:p></SPAN></div>  <div><SPAN style="FONT-SIZE: 10pt; \
FONT-FAMILY: Arial">I have a strange problem using quadrature in comedi: not so \
random noise. The measure at a constant rotation rate is almost a straight line. When \
taken a difference between two consecutive points for speed, it exhibits some error \
for less than 1% of the points. For these points the velocity can vary up to 20% of \
speed value, while the rest of the points are well on target.<o:p></o:p></SPAN></div> \
<div><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">&nbsp;<o:p></o:p></SPAN></div> \
<div><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">I am using a <?xml:namespace \
prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" /><st1:country-region  \
w:st="on"><st1:place w:st="on">US</st1:place></st1:country-region> digital encoder \
512 pulse per rotation. I also tried a totally different encoder with similar result. \
The axis rotation rate is 700 rpm. The board is a Sensoray 526 PC104. Software is \
Linux 2.6.17, RTAI 3.4 test1 and comedi-0.7.73 and comedilib-0.7.72. \
<o:p></o:p></SPAN></div>  <div><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: \
Arial">&nbsp;<o:p></o:p></SPAN></div>  <div><SPAN style="FONT-SIZE: 10pt; \
FONT-FAMILY: Arial">Any suggestions are welcome, :-D<o:p></o:p></SPAN></div>  \
<div><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">&nbsp;<o:p></o:p></SPAN></div> \
<div><st1:City w:st="on"><st1:place w:st="on"><SPAN style="FONT-SIZE: 10pt; \
FONT-FAMILY: Arial">Everett</SPAN></st1:place></st1:City><SPAN style="FONT-SIZE: \
10pt; FONT-FAMILY: Arial"><o:p></o:p></SPAN></div>  <div class=MsoNormal \
style="MARGIN: 0in 0in 0pt"><o:p><FONT face="Times New Roman" \
size=3>&nbsp;</FONT></o:p></div>  <div>&nbsp;</div>


_______________________________________________
comedi mailing list
comedi@comedi.org
https://cvs.comedi.org/cgi-bin/mailman/listinfo/comedi

[prev in list] [next in list] [prev in thread] [next in thread]