In a message dated 29/03/2007, tchannel@.............. writes:

Hi Folk,  This may not be a problem, not  sure....I moved things around, and 
changed two pieces of  equipment.
Someone gave me a DataQ 194 AD converter, and a  computer. I relocated all 
the equipment to a different location.  Installed the AD board, and got 
everything up and running again.   Everything seemed normal, but recorded my first 
event and on the Helicorder  screen of AmaSeis, and only the center and top half 
of the event is  seen.  The bottom half of the event is cutoff just below the 
center line,  like it was "clipped".    I processed the event and after  
filtering it, in the normal way, the bottom half was then visible, so the  final 
..GIF looks just fine.
 
I looked at the sensor which is a Vertical Spring  sensor, to see if it was 
free to move up and down, and it was.
I checked the magnetic damper, and all seems  normal.
 
It is a new "old computer" and the new "old DataQ  AD board, everything else 
is the same.
I did have to install, software on the new  computer, AmaSeis, Winquake, and 
DataQ.
 
All this being said, if I enlarge a small piece  of quiet trace, it is not 
clipped.
If I do a drop test on the floor, The spike go up  and very little down, just 
like the event trace, yet the sensor will produce a  negative and positive 
spike if I force it by blowing on it.  Again only  an (above the line) spike 
using a drop test.
 
I did recalibrate the DataQ and rezero the  AmaSeis.
 
Any ideas?   Thanks,  Ted



Hi Ted,
 
    I suggest that you check the full +/-10V input  range of the DI-194 for 
operation. Do you have the Dataq display software?  They have been know to 
fail. Check that link JP2 is on the two pins furthest  away from the terminal 
block. 
 
    Check that your +&- amplifier power lines are  OK.
 
    I suspect that filtering may remove any DC offset.  Chcck whether after 
filtering you have ~1/2 the amplitude?
 
    Alteratively, can your amplifier output cope with  the small current 
input requirement of the DI-194, approx 10 micro  A?  I seem to remember that the 
open circuit offset is about 2.5  V / 3 micro A? I got 'caught out' when 
trying to drive one from a 27 K Ohm  source - I had added a RC filter to the final 
opamp to increase the roll  off.
 
    Regards,
 
    Chris Chapman



   






In a message dated 29/03/2007, tchannel@.............. writes:
<=
FONT=20
  style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>
  
Hi Folk,  This may not be a problem,=
 not=20
  sure....I moved things around, and changed two pieces of=20
  equipment.
  
Someone gave me a DataQ 194 AD converter,=
 and a=20
  computer. I relocated all the equipment to a different location.=20
  Installed the AD board, and got everything up and running again. =20
  Everything seemed normal, but recorded my first event and on the Helicorde=
r=20
  screen of AmaSeis, and only the center and top half of the event is=20
  seen.  The bottom half of the event is cutoff just below the center l=
ine,=20
  like it was "clipped".    I processed the event and af=
ter=20
  filtering it, in the normal way, the bottom half was then visible, so the=20
  final .GIF looks just fine.
  
 
  
I looked at the sensor which is a Vertica=
l Spring=20
  sensor, to see if it was free to move up and down, and it was.
  
I checked the magnetic damper, and all se=
ems=20
  normal.
  
 
  
It is a new "old computer" and the new "o=
ld DataQ=20
  AD board, everything else is the same.
  
I did have to install, software on the ne=
w=20
  computer, AmaSeis, Winquake, and DataQ.
  
 
  
All this being said, if I enlarge a small=
 piece=20
  of quiet trace, it is not clipped.
  
If I do a drop test on the floor, The spi=
ke go up=20
  and very little down, just like the event trace, yet the sensor will produ=
ce a=20
  negative and positive spike if I force it by blowing on it.  Again on=
ly=20
  an (above the line) spike using a drop test.
  
 
  
I did recalibrate the DataQ and rezero th=
e=20
  AmaSeis.
  
 
  
Any ideas?   Thanks,=20
  Ted

Hi Ted,
 
    I suggest that you check the full +/-10V input=20
range of the DI-194 for operation. Do you have the Dataq display softwa=
re?=20
They have been know to fail. Check that link JP2 is on the two pins furthest=
=20
away from the terminal block. 
 
    Check that your +&- amplifier power lines a=
re=20
OK.
 
    I suspect that filtering may remove any DC offs=
et.=20
Chcck whether after filtering you have ~1/2 the amplitude?
 
    Alteratively, can your amplifier output cope wi=
th=20
the small current input requirement of the DI-194, approx 10 micro=20
A?  I seem to remember that the open circuit offset is about=20=
2.5=20
V / 3 micro A? I got 'caught out' when trying to drive one from a 27 K=20=
Ohm=20
source - I had added a RC filter to the final opamp to increase the roll=20
off.
 
    Regards,
 
    Chris Chapman