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Re: The Amateur Scientist and Interesting Measurements

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Mike Preston
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-----Original Message-----
From: Doug Sutherland <>
To:  <>
Date: 07 January 2001 19:33
Subject: The Amateur Scientist and Interesting Measurements

>wear-hards,
>
>I have always found the column "Amateur Scientist" in
>Scientific American magazibe to be interesting. They
>have in the past had plans and instructions to build
>all kinds of measurement devices like seismometers
>and magnetic field detectors etc. Yesterday I looked
>through all of the archived pasts issues for ideas
>for wearable instrumentation. Here is a circuit that
>I have been seeking for a long time, it shows how to
>build an ECG (heart monitor) using an instrumentation
>amplifier (Analog Devices AD624AD).
>
>Home Is Where the ECG Is
>http://www.sciam.com/2000/0600issue/0600amsci.html
>
>This circuit should do a good job at monitoring cardio
>activity, but it does not digitize the data, it needs
>an Analog/Digital Converter that can sample at 100hz
>or better (twice the largest frequency produced). The
>BX24 microcontrollers that I am using have 10-bit A/D
>converters built-in, and I also have a bank of eleven
>12-bit A/D converters uusing the TLC2543CN attached to
>a PIC microcontroller. But looking at the specs for
>both I can't seem to determine if they are capable of
>handling the 100hz sampling. I'm wondering if there are
>any analog savvy folks out there who could help me
>answer these three questions:
>
>1) I'm trying to determine of the BX24s onboard ADCs
>   are capable of handling this cardio circuit. The
>   only specs I can find indicate that they are
>   10-bit resolution with a sampling rate of 6000

6000samples = 3000Hz max frequency.....

adequate!

>   samples per second. Here is the sparse data sheet:
>   http://www.basicx.com/bx24specs.htm
>
>2) I'm trying to determine if the TLC2543CN ADC chip
>   is capable of handling this cardio circuit. There
>   are tons of specs in the data sheet, but I don't
>   know which one to look at to determine if it can
>   handle the 100hz sampling. I know that the ADCs
>   are 12-bit resolution, the sampling rate is 66k

66000samples/sec = 33000Hz max......

better than the CD

>   samples per second, and the IO clock is 4.1 MHz.
>   But I can't tell which spec needs to meet the
>   100hz capability. Here's the specs:
>
http://focus.ti.com/docs/prod/productfolder.jhtml?genericPartNumber=TLC2543
>
>3) If neither of these are capable of handling the
>   100hz sampling frequency, can anyone recommend an
>   ADC that will be good enough? The article suggests
>   that I can find appropriate ADCs at both National
>   Instruments and Vernier Software, but I really
>   don't know what I am looking for. Any ideas?

SNIP seismic intro

>I also want to mention that I have the radio telemetry
>demodulator board from Larry. The USGS has seismic stations
>that send their data over radio, and a normal scanner can
>read the data, pass it to the demodulator board, then it
>looks exactly like a physical seismometer, but you are
>getting the data from professional USGS seismos over the
>radio waves:
>
>http://www.seismicnet.com/telebrd.html
>http://www.seismicnet.com/info/telemtry.txt
>
>I was hoping to be able to receive radio telemetry data
>via radio scanner here, especially since there are seismic
>stations within 5 or 6 miles of my house, but I can't get
>any signals. My location is poor for radio because I am
>surrounded by large redwoods in a canyon. I hate the
>fact that this radio scanner and telmetry board is just
>sitting here doing nothing. So I am wondering if anyone
>in the SF bay area wants to try it out. I can give you
>the radio scanner to look for the continuous tone that
>USGS sends out. If the tone is present, I can give you
>the telemtry board. The only other required parts to
>make it a complete seismo is a cheap PC and the A/D
>Converter card listed above. If anyone wants to try this
>let me know. Perhaps we can find a way to feed seismic
>data from both my station and another location running
>telemtry aquisition data to the internet, and display
>the real-time data on our wearables ...
>
>  -- Doug

Okay.....if you do do this.....and have measurements from three (or more)
stations, you can easily calculate the epi-centre......no need to wait for
the news report anymore!

This would be a nice project....although in most of the UK it is pretty
pointless.....

I on the other hand live 5 miles from an extinct volcano.....we still get
some fair size tremors

:0)

mike
>
>
>------------------------------------------------------------
>  Grow your own Wearables: http://wearables.los-gatos.net
> What I'd like is to have you call me and my jacket answers
>------------------------------------------------------------
>
>
>
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