Hello Ted:

For those negative clipped at zero outputs.
You might have to add between the amp
and the A/D an op amp which
floats at half B+ (Half B+ being Zero on the output,
then sums the output of
what you are looking at. Then Larry's
A/D boards which look at +/- power schemes
should work within +/- 5 to 10 volts Peak.

In other words an adaptor circuit of some kind.

I am now using Larry's 16bit Board which is  much better
For This Purpose than the other one I was using.

Programming the board is a challenge unless you
can understand the DLL which seems to be directly
talking to the A/D board.
The stimuli and responses of the board.
The various commands so to speak.
The microcode on the A/D board.
At the moment I will not try a custom program for the board
because it works A-Ok as it is with his software.

If Larry's Boards were universal it would allow
a mode for single supply class "A" operation.

At the moment it is sort of like class "B"
Push-Pull. Or, Class "A" Double Supply.

Single Supply Class "A" (360deg reproduction)
amplifier, although it produces
the most faithful reproductions,
is a power hog.

Class "B" (180deg reproduction) is more power friendly
yet produces slight distortions in the output where
it crosses zero.

As you can guess, Class "B" Push Pull which seems to be
the case for Operational Amplifiers, is two amplifiers
internal to the chip,
each reproducing one half the wave form with both
resting at zero between the two supplies.

There might be new ideas today which I have never heard of.
My formal education is quite old.

Regards,
geoff

-----Original Message----- 
From: Ted Channel
Sent: Thursday, October 21, 2010 12:16 AM
To: psnlist@..............
Subject: Negative clipping in AmaSeis


Hi Folks,   I have used DataQ194 ad converters, and 158.   Big price differences so I use more of the 194.

Mostly they work fine.   However from time to time a system will have negative clipping, nothing below zero, unless you jump close 
to the machine and then is shows negative values.

We installed a new system, in a school three hours away.    They recorded their first earthquake, but because of the clipping the 
data is useless.   It carrys over into Winquake and filtering does nothing to improve it.

I had a similar problem, changed the 194, and install a 158 the problem went away.   Reinstalled the 194, the problem returned.   I 
wanted to try a new 194, but did not have one.

Can anyone help........Have you see something similar?....could it be the set up procedure in Windata, which comes with the 194. 
It has a set up window for values, and should be set to +10 volts and -10 volts.

I don't think it is the sensor.
I don't think it is Amaseis or Winquake.
I don't think it is the computer.
I don't think it is the cables......

Thanks, Ted 

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