re SEISMOMETER

From: "John Scott" <j.p.scott@xxxxxxxxxxxxxx>
Subject: Fw: SEISMOMETER
Date: 29 May 2005 23:49

> To the group,

> The seismic head has three separate transducers known as geophones. These
> signals are sent to three separate low frequency low noise fixed gain
> amplifiers before being presented to the first. second, and third inputs
> of the main board, where they are filtered before being presented to the
> first,second, and third inputs of the four channel ADC sigma delta chip
> the AD7716
>
> Ch1 senses vertical motion.
> Ch2 sense east-west motion
> Ch3 senses north_south motion
>
> The digital outputs of these three channels are interlaced and sent via
> rs232 to a pc.
>
> The highest frequency of interest is 512Hz.
>
> The equipment has not yet been designed but it is necessary to look at the
> programming capabilities available to work with various possibilities in
> the way of hardware.
>
> Essential main board hardware would include a microprocessor with an
> eprom. In an old seismometer this could be a mc68hc705.
> In a newer seismometer it could be a 16 bit device.
>
> The protocols are yet to be laid down.
>
> The host computer seismic program would comprise of
>
> Seismometer ini setup file to select the rs232 port, the gain of each
> channel, the channel from which the trigger is to be taken from, and the
> trigger level: and other factors to be stated later.
>
> The start sampling signal is from a leyboard designated key, as is also
> the stop sampling signal, reset and quit signals.
>
> The host program contains software to display the velocity and frequency
> traces of the seismic wave in terms of vertical, eastwest and northsouth
> parameters. It is capable of a great deal of analysis of each of the three
> displays.
>
> THE MICROPROCESSOR CONTROLS THE AD7716 and a suitable program would be
> embedded in the eprom.
>
> Ideas about an appropriate microcontroller are being sought now. The
> AD7716 will be used for the sampling.
>
> Regards John Scott
>
>
>


.

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