PSN-L Email List Message

Subject: Re[2]: Hekla volcano geophone planned
From: Angel sismos@..............
Date: Sat, 5 Jan 2008 16:13:08 +0000

Hello Ian,

Just to get an idea,  how many PSN-ADC-SERIAL Version II with GPS timing and full time internet connection are there out there.

I have one.


Saturday, January 5, 2008, 3:57:40 PM, you wrote:

> 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

> 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 
>>> ).
>>> 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
>>>> .

>>>> 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,


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