Searching \ for 'Measuring stuff with PICs' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: techref.massmind.org/techref/microchip/devices.htm?key=pic
Search entire site for: 'Measuring stuff with PICs'.

Truncated match.
PICList Thread
'Measuring stuff with PICs'
1998\06\24@011320 by tjaart

flavicon
face
Hi All

I am thinking of getting involved in a local drive to
conserve some of our indigenous fish. A big problem
with our river systems is that is is controlled without
much thought on the biological implications. For
instance dumping a huge amount of water into a river
during the breeding season is bad for the procreation.
(Think how *you* would feel if someone emptied
a bucket of cold water on you and your partner!)

To get to the point, we need some way of collecting
data of the water conditions. These would include
water level, temperature, visibility, air temperature,
ambient light and barometric pressure.

Temperature and visibility and ambient light would
be easy to measure. How does one measure a river's
water level (2.5m change) without little contacts that
will corrode?

My idea is to put a vertical pipe with a hole in the
bottom into the water. A speaker (with a plastic
cone) is placed at the top of the pipe and the
frequency sweeped from the low resonant frequency
to the high resonant frequency. I could detect the
peak amplitude with an electret microphone.
What do you think?

BTW what sort of a sensor would be able to measure
barometric pressure? I am going to pay for this, so it
had better be cheap!

--
Friendly Regards

Tjaart van der Walt
spam_OUTtjaartTakeThisOuTspamwasp.co.za

Add your voice !!
Vote at the Great G Com Public Vote. Go to :
http://www.wasp.co.za/~tjaart/gcomvote.html

|--------------------------------------------------|
|                WASP International                |
|R&D Engineer : GSM peripheral services development|
|--------------------------------------------------|
|SMS .....0832123443KILLspamspam@spam@wasp.co.za  (160 chars max)|
|     http://www.wasp.co.za/~tjaart/index.html     |
|Voice: +27-(0)11-622-8686  Fax: +27-(0)11-622-8973|
|          WGS-84 : 26¡10.52'S 28¡06.19'E          |
|--------------------------------------------------|

1998\06\24@021033 by James Cameron

picon face
Tjaart van der Walt wrote:
> How does one measure a river's water level (2.5m change) without
> little contacts that will corrode?

Use little contacts that will not corrode.  Keep them at identical
potential for most of the time and only raise them to make measurements,
or place a sacrificial anode nearby and keep the contacts at least a
little bit on the "right" side of the anode.

> My idea is to put a vertical pipe with a hole in the
> bottom into the water. A speaker (with a plastic
> cone) is placed at the top of the pipe and the [...]

Hmm.  Never thought of peak frequency measurement.  I'd simply bounce a
pulse down the tube and recognise the peak return.  Time for the bounce
is distance.

> BTW what sort of a sensor would be able to measure
> barometric pressure?

Pass.  Last I checked it was expensive.

--
James Cameron                              (james.cameronspamKILLspamdigital.com)
Digital Equipment Corporation (Australia) Pty. Ltd. A.C.N. 000 446 800

1998\06\24@023710 by Clyde Smith-Stubbs

flavicon
face
On Wed, Jun 24, 1998 at 07:14:16AM +0200, Tjaart van der Walt wrote:

> Temperature and visibility and ambient light would
> be easy to measure. How does one measure a river's
> water level (2.5m change) without little contacts that

Use a pressure sensor with a pipe going to the bottom of the river. I've
got this set up with some water tanks - still some calibration issues, but
the basic concept works well, and there is no electronics in the water.
You do need an air pump to purge the tube. An alternative would be
an absolute pressure sensor encapsulated and dropped to the bottom
and referenced against a similar sensor in air.

For a pump I ended up using a 12V automotive tyre pump - one pump supplies
two tubes via check valves (fish tank type). Fish tank pumps have too low
a pressure output to work for more than about 500mm of water.
The plumbing hardware is basically 6mm irrigation tubing and barb connectors.

There's a piccy of the setup at http://www.htsoft.com/images/tanksense.jpg

> frequency sweeped from the low resonant frequency
> to the high resonant frequency. I could detect the
> peak amplitude with an electret microphone.

This might work, but it sounds a little touchy to set up to me. You
could probably measure the speaker impedance rather than using a
microphone.

> BTW what sort of a sensor would be able to measure
> barometric pressure? I am going to pay for this, so it

Honeywell have small pressure sensors - they're not too expensive. They
are a bridge setup with a diaphragm and strain gauges, excited with 5-10V
and output is differential, in the mV range.

(Thanks to Bob Blick for the sensors, op-amps and ideas). Onya Bob!

Cheers, Clyde

--
Clyde Smith-Stubbs               |            HI-TECH Software
Email: .....clydeKILLspamspam.....htsoft.com          |          Phone            Fax
WWW:   http://www.htsoft.com/    | USA: (408) 490 2885  (408) 490 2885
PGP:   finger EraseMEclydespam_OUTspamTakeThisOuThtsoft.com   | AUS: +61 7 3354 2411 +61 7 3354 2422
---------------------------------------------------------------------------
HI-TECH C: compiling the real world.

1998\06\24@023933 by Dennis Plunkett

flavicon
face
At 03:58 PM 24/06/98 +1000, you wrote:
{Quote hidden}

Firstly I am assuming that the range you are after is 2.5m, not a change
from x to x + 2.5m

Ah, it all sounds so simple! There have been many attempts to derive an
ultrasonic depth gauge, most do work, however the current drain is high. You
may wish to look at the ones made by Kodak. As for your idea of a plastic
pipe and speaker, yeah, it will work but with vary limited success due to
variations in temperature, atmospheric temperature drumming in the pipe due
to wind and other general activities on the water eg boating, yet alone the
problems that you will have with keeping the pipe inlet unclogged and wave
action.

If the money is coming out of your own pocket, then you may wish to look at
other methods. The first question is do you have mains power, if so then a
simple float on a cheep optical encoder will do the job (You can purchase
quadrature shaft encoders, but they need a well or bubbler system to
operate). If you want to have more fun, then look at a silicon strain gauge
that Motorola make, with this you could make a vented differential pressure
transducer (Hint hint for the barometric one, note that there are some cheep
voltage type sensors here that you could use to and mount directly on a
PCB!). But the ultimate way to measure the depth is with a pressure
transducer (Vented) these can be obtained from Transmetrics or Druck, in
either submersible or dry.

Effectively you are after a whether station, if you have the bucks to spend,
then look for "ALERT" equipment on the WEB (Around $3000, and it will log
the data to, only some not all!), this is the cheapest form of remote radio
based stuff (Will also measure rainfall (Bonus)). Other than that there are
a few companies that make the sensors and data loggers that you're after try
Unidata


Dennis
-=====================================================================-

Dennis Plunkett: Embedded Hardware, Software design
NEC Australia
ph 03 9264-3867

-=====================================================================-

1998\06\24@045229 by tjaart

flavicon
face
Dennis Plunkett wrote:

> >Hmm.  Never thought of peak frequency measurement.  I'd simply bounce a
> >pulse down the tube and recognise the peak return.  Time for the bounce
> >is distance.

This would impose a resolution constraint on the measurement.If I check the peak amplitude (in the
current as suggested by
Clyde, or the output voltage envelope of an electret microphone),
I think the resolution constraint only comes in when measuring the
amplitude, not in the actual distance  What do you think?.

Dennis Plunkett also wrote


> Firstly I am assuming that the range you are after is 2.5m, not a change
> from x to x + 2.5m

It actually would be for a change. Total range I'd like would besomething like 3m

> Ah, it all sounds so simple! There have been many attempts to derive an
> ultrasonic depth gauge, most do work, however the current drain is high. You
> may wish to look at the ones made by Kodak. As for your idea of a plastic
> pipe and speaker, yeah, it will work but with vary limited success due to
> variations in temperature, atmospheric temperature drumming in the pipe due
> to wind and other general activities on the water eg boating, yet alone the
> problems that you will have with keeping the pipe inlet unclogged and wave
> action.

I'd make the hole right at the bottom, with a 1mm breathing holeat the top to reduce wave effect. I
can guarantee that no person
with anything between his ears would attemp any watersports on
this particular river. The bottom is probably 50% rocks and
boulders, with the water level changing at a tens of centimeters/hour.


> If the money is coming out of your own pocket, then you may wish to look at
> other methods. The first question is do you have mains power, if so then a
> simple float on a cheep optical encoder will do the job (You can purchase
> quadrature shaft encoders, but they need a well or bubbler system to

Wilt this work over a 2.5m range?

> operate). If you want to have more fun, then look at a silicon strain gauge
> that Motorola make, with this you could make a vented differential pressure
> transducer

Hmm. This could be a good starting point.

> (Hint hint for the barometric one, note that there are some cheep
> voltage type sensors here that you could use to and mount directly on a
> PCB!).

Who makes these?

>  Effectively you are after a whether station, if you have the bucks to spend,
> then look for "ALERT" equipment on the WEB (Around $3000, and it will log
> the data to, only some not all!), this is the cheapest form of remote radio
> based stuff (Will also measure rainfall (Bonus)). Other than that there are
> a few companies that make the sensors and data loggers that you're after try
> Unidata

Ha! with you guys ruining our rand value, $3000 is way, way,way out of my reach!


Clyde Smith-Stubbs wrote:

> Use a pressure sensor with a pipe going to the bottom of the river. I've
> got this set up with some water tanks - still some calibration issues, but
> the basic concept works well, and there is no electronics in the water.
> You do need an air pump to purge the tube. An alternative would be

> an absolute pressure sensor encapsulated and dropped to the bottom
> and referenced against a similar sensor in air.

If they aren't too expensive, I can get the barometric pressure fromthe dry one. What do they go
for?

{Quote hidden}

Thanks for your inputs

--
Friendly Regards

Tjaart van der Walt
@spam@tjaartKILLspamspamwasp.co.za

Add your voice !!
Vote at the Great G Com Public Vote. Go to :
http://www.wasp.co.za/~tjaart/gcomvote.html

|--------------------------------------------------|
|                WASP International                |
|R&D Engineer : GSM peripheral services development|
|--------------------------------------------------|
|SMS KILLspam0832123443KILLspamspamwasp.co.za  (160 chars max)|
|     http://www.wasp.co.za/~tjaart/index.html     |
|Voice: +27-(0)11-622-8686  Fax: +27-(0)11-622-8973|
|          WGS-84 : 26¡10.52'S 28¡06.19'E          |
|--------------------------------------------------|

1998\06\24@073121 by Timothy D. Gray

flavicon
face
You can bounce an ultrasonic wave at it without a pipe, or use an air
bubbler and measure the air pressure change, use a float attached to a
string and a variable resistance, use 2 stainless steel electrodes (Highly
inaccurate as condictivity of water varies greatly in a river), there are
thousands of ways to measure fluid level, check out an industrial catalog
of sensors.

On Wed, 24 Jun 1998, James Cameron wrote:

{Quote hidden}

1998\06\24@122017 by John Miller

picon face
Check out our website http://www.senix.com
We make ultrasonic sensors that provide analog outputs and/or RS232
outputs.

Senix Corporation
52 Maple Street
Bristol, VT
05443
1-800-67-SENIX

----------
> From: Timothy D. Gray <spamBeGonetimgrayspamBeGonespamLAMBDANET.COM>
> To: TakeThisOuTPICLISTEraseMEspamspam_OUTMITVMA.MIT.EDU
> Subject: Re: Measuring stuff with PICs
> Date: Wednesday, June 24, 1998 7:29 AM
>
> You can bounce an ultrasonic wave at it without a pipe, or use an air
> bubbler and measure the air pressure change, use a float attached to a
> string and a variable resistance, use 2 stainless steel electrodes
(Highly
{Quote hidden}

measurements,
{Quote hidden}

1998\06\25@143055 by Andres j Ogayar

flavicon
face
Tjaart,

   An idea: go to your next Fry's electronic shop. Buy a CASIO altimeter
clock (or something cheaper), and use the transducer... it will be around
$50.

   Of course, this sensor probably doesn't respond to a couple of meters
difference... Will it?

   Andres j. Ogayar

1998\06\26@090300 by tjaart

flavicon
face
It seems like Bob Blick had the best idea for the
cheapest way of measuring water level in a pipe.

There is an application note for the LM3909
that describes a setup (electronic trombone)
whereby a speaker will emit a sound tone at the
resonant frequency of the sound box. I only have
to measure this frequency with a PIC to get the
water level.

I will obviously have to experiment a bit to see
how repeatable and reliable it is.

Thanks Tom, Bob, Clyde, and the other folks who
have helped so far.

--
Friendly Regards

Tjaart van der Walt
tjaartEraseMEspam.....wasp.co.za

Add your voice !!
Vote at the Great G Com Public Vote. Go to :
http://www.wasp.co.za/~tjaart/gcomvote.html

|--------------------------------------------------|
|                WASP International                |
|R&D Engineer : GSM peripheral services development|
|--------------------------------------------------|
|SMS EraseME0832123443spamwasp.co.za  (160 chars max)|
|     http://www.wasp.co.za/~tjaart/index.html     |
|Voice: +27-(0)11-622-8686  Fax: +27-(0)11-622-8973|
|          WGS-84 : 26¡10.52'S 28¡06.19'E          |
|--------------------------------------------------|

More... (looser matching)
- Last day of these posts
- In 1998 , 1999 only
- Today
- New search...