Hello Ian,

I have not read each messages of this thread careful but I will. All of the software needed to link a large distributed seismic system is free and freely available.

Anyone who has one of Larry's 16 bit 8 channel boards with GPS (wwv) timing and a full time internet connection can share data and PSN can a global or regional system auto locating system.  

Angel



Saturday, January 5, 2008, 9:35:41 AM, you wrote:

> Hi,

> actually, I don't think I'm near any limits.  The A/D I use can handle
> 20K samples/sec.  I only have 2 instruments (though I sample each on 3
> A/D channels to get the resolution up to 22 bits), so that's only 6 x 
> 50, or 300 samples/sec.  So I could connect up all of the A/D's 16 input
> channels and still not stress it.

> The data server does burn up 80% of the PC's CPU but it's only an old 
> 800 MHz machine and wouldn't cost much to replace with one twice the 
> speed.  Data across the network connection is only 32 characters x 50 or
> 1600 bytes/sec.  Less than a 500th of the 100 Mb/s network bandwidth 
> (being generous).

> All of the above though, implies that you are happy to write your own 
> code.  Buying building blocks off the shelf can be very attractive. For
> multiple instruments you could buy several PSN A/D boards.  To overcome
> the potential problem of connecting up multiple RS232 cables, you could
> use a network terminal server (such as 
> http://www.perle.com/products/IOLAN-STS-Terminal-Server.shtml?rack ).
> These aggregate up to 4/8/16/24 rs232 connections on to one network 
> connection.  They usually come with software for the pc which creates 
> multiple virtual COM ports, so your A/D boards would look like they are
> plugged into an array of COM ports on the PC.

> Isn't technology wonderful!

> Cheers

> Ian

> ChrisAtUpw@....... wrote:
>> In a message dated 04/01/2008, gpayton880@....... writes:

>>     But rather than have 1 sensor on a single socket it is more
>>     sensible to
>>     have many sensors on a single socket using a data protocol.  This
>>     is how
>>     I have designed my system.  It sends out a continuous stream (50
>>     samples
>>     per second) of "(Lehman reading) (geophone reading) (time
>>     stamp)".  My
>>     graphing program makes a connection to the "data server" and plots
>>     the
>>     values from the 2 sensors as they arrive.  See
>>     http://www.iasmith.com .

>> Hi Ian,
>>  
>>     The limitation tends to be the total data throughput 
>> speed reqired. 50 SPS is quite fast. The ADC sample rate can also 
>> impose limitations. This starts to become serious when you have, say 
>> several three off three channel sensors on the same ADC.
>>  
>>     Regards,
>>  
>>     Chris Chapman




-- 
Best regards,
 Angel

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