RE: The Amateur Scientist and Interesting Measurements

From: Edmund Troche <
>
Date: Wed, 10 Jan 2001 18:22:04 -0500

Doug,

This is great info. I had been looking for this for a while, but with no
luck. I do remember an old issue of Radio Electronics that had an article
about building an EKG machine (also how to interpret the PQRST portions of
the wave form). I wish I could find it. Anyway, your references below got me
encouraged to build an EKG device. Have you started building yours? If you
have, which way did you decide to go, using Vernier's or building the one
from the article? I have not been able to locate a supplier for the AD624AD.
If you, or anyone in the list have started some work in this area, please
send some feedback. 

Thanks,

Edmund

-----Original Message-----
From: Doug Sutherland [mailto:]
Sent: Sunday, January 07, 2001 11:34 AM
To: 
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
   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
   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?

Here are a few other "Amateur Scientist" columns that I 
thought were interesting:

Recording the Sounds of Life
http://www.sciam.com/1097issue/1097amsci.html

Home Movies of an Invisible World
http://www.sciam.com/1998/1098issue/1098amsci.html

Detecting "Hot" Clouds
http://www.sciam.com/1999/0499issue/0499amsci.html

When Hazy Skies are Rising
http://www.sciam.com/0597issue/0597amsci.html

Weather on the Web
http://www.sciam.com/specialissues/0300weather/0300stix.html

BTW since I am on the topic of instrumentation, I thought
I'd mention that it's possible to have your own seismic 
station for not too much money. I have one, it consists of
two geophones (normally used for oil exploration) feeding 
into an amplifier/filter circuit and then into a 16-bit 
A/D Converter. This system was designed by Larry Cochrane
who is here is Redwood City CA. I have been to house and 
it's a lot like mine: wires, tools, and monitors everywhere.
He is really serious about measuring quakes, he has all
kinds of seismometers set up and coaxial cables running 
right across his living room floor etc. One of these day
I want to figure out how to feed real-time data from my 
seismometer to my wearable over the net and show the data
charts on my sleeve LCD. 

If you are interested in measuring quakes, it can be 
affordable, all you need is an old PC running DOS and 
the following parts from Larry;

 - Seismic Amplifier/Filter Board ($100 - $190)
   http://www.seismicnet.com/eqamp.html

 - 12/16 Bit Analog Digital Converter Board ($180 - $245)
   http://www.seismicnet.com/atod.html

 - It's also recommended to have GPS for timing ($220)
   http://www.seismicnet.com/gps/index.html
   (I hoisted this from my seismo and it's on my wearable)

In addition to these parts all you need is an old PC and 
one or more geophones (I got mine used for cheap), or you 
can build your own seismometer:
http://www.seismicnet.com/info/homefaq.txt

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

------------------------------------------------------------
  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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