PSN-L Email List Message

Subject: Re: Hekla volcano geophone planned
From: ian ian@...........
Date: Sat, 05 Jan 2008 15:57:40 +0000


Hi,

yes, you're right, all free.  I was really addressing the earlier 
(possibly hypothetical) question of how to connect many sensors to 1 
network connection.  The engineer in me probably made my response a bit 
enthusiastic and suitable for connecting dozens of sensors.

Back to (free) reality!

Cheers

Ian
http://www.iasmith.com/
http://www.festivalpreviews.com

Angel wrote:
> 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
>>>       
>
>
>
>
>   

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