sonar measurements
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Has anyone used sonar to measure the distance of an object above
water or other liquids? I need to measure a liquid level which will
change from 3 to 10 feet.
While I am asking, would sonar work with a granular surface? I want
to measure the level of grain in a grain bin so there will be metal
walls and ceiling reflecting signals around. Can I get enough echo
off the grain without the signal bouncing around inside the bin
messing things up?
If so, how about infrared? Any ideas are welcome.
Thanks in advance
water or other liquids? I need to measure a liquid level which will
change from 3 to 10 feet.
While I am asking, would sonar work with a granular surface? I want
to measure the level of grain in a grain bin so there will be metal
walls and ceiling reflecting signals around. Can I get enough echo
off the grain without the signal bouncing around inside the bin
messing things up?
If so, how about infrared? Any ideas are welcome.
Thanks in advance
Comments
>Has anyone used sonar to measure the distance of an object above
>water or other liquids? I need to measure a liquid level which will
>change from 3 to 10 feet.
>
>While I am asking, would sonar work with a granular surface? I want
>to measure the level of grain in a grain bin so there will be metal
>walls and ceiling reflecting signals around. Can I get enough echo
>off the grain without the signal bouncing around inside the bin
>messing things up?
>
>If so, how about infrared? Any ideas are welcome.
Hang a small weight over a pulley attached to a micro switch so the weight
trips the micro switch. From the home position, lower the weight until the
switch "untrips" because the weight is no longer supported; i.e., has come
to rest on the grain. Count pulses to a stepper motor needed to achieve
this result and convert to depth. Retract weigh to home position until
next measurement is needed. Properly done the whole mechanism can be
outside the silo with only a tiny hole for the line. The weight stays
inside. Steel weight, not lead since grain is edible. You can assure
proper home position by tripping a second micro switch that needs more
weight/resistance to trip so when the weight retracts against the top of
the tank this switch tells the controller to stop retracting. Trip weights
are set using springs with different tensions. Simple, non fouling, very
low maintenance, essentially foolproof calibration.
Jim H
Wouldn't be worried about so many moving parts exposed to wear
& weather? I would.
Ken Ambrose
with enough thrust, pigs fly just fine.
---- On Fri, 26 Oct 2001, Jim Higgins (HigginsJ@s...)
wrote:
> At 20:16 10/26/01, stujo wrote:
>
> >Has anyone used sonar to measure the distance of an object
above
> >water or other liquids? I need to measure a liquid level
which will
> >change from 3 to 10 feet.
> >
> >While I am asking, would sonar work with a granular surface?
I want
> >to measure the level of grain in a grain bin so there will
be metal
> >walls and ceiling reflecting signals around. Can I get
enough echo
> >off the grain without the signal bouncing around inside the
bin
> >messing things up?
> >
> >If so, how about infrared? Any ideas are welcome.
>
> Hang a small weight over a pulley attached to a micro switch
so the
> weight
> trips the micro switch. From the home position, lower the
weight until
> the
> switch "untrips" because the weight is no longer supported;
i.e., has
> come
> to rest on the grain. Count pulses to a stepper motor needed
to achieve
>
> this result and convert to depth. Retract weigh to home
position until
> next measurement is needed. Properly done the whole
mechanism can be
> outside the silo with only a tiny hole for the line. The
weight stays
> inside. Steel weight, not lead since grain is edible. You
can assure
> proper home position by tripping a second micro switch that
needs more
> weight/resistance to trip so when the weight retracts against
the top of
>
> the tank this switch tells the controller to stop
retracting. Trip
> weights
> are set using springs with different tensions. Simple, non
fouling,
> very
> low maintenance, essentially foolproof calibration.
>
>
> Jim H
>
>
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weight
> trips the micro switch. From the home position, lower the weight until
the
> switch "untrips" because the weight is no longer supported; i.e., has
come ...
Interesting idea. Sometimes grain bins fill pretty rapidly. If the weight
were buried the system might not be able to easily pull it free from the
grain.
Tim
> > Hang a small weight over a pulley attached to a micro switch so the
>weight
> > trips the micro switch. From the home position, lower the weight until
>the
> > switch "untrips" because the weight is no longer supported; i.e., has
>come ...
>
>Interesting idea. Sometimes grain bins fill pretty rapidly. If the weight
>were buried the system might not be able to easily pull it free from the
>grain.
Yes, but if that much grain is flooding in that fast, falling from the top
I assume, you can be pretty sure that sonar and infrared will be totally
useless because the air between top and surface of grain will be dense with
grain. If the weight is shaped appropriately, it can be pulled free,
although this system isn't really meant to measure during a fast filling
operation that could trap the weight beyond the ability to retrieve it. (I
had forgotten that.) You can include logic to stop filling and keep
pulling if the weight is down by X counts and the "home position" sensor
trips well before X counts have been counted back off in the upward
direction. Home sensor trips when there is a very strong drag on the
weight. You can optionally add a second "home" sensor at the top that is
tripped by the actual presence of the weight and require both be tripped to
confirm home. One tripped and it means the weight is hung in the grain and
you just keep pulling (and maybe stop filling temporarily). You can also
take a few measurements of fill rate and when you do fill, measure first,
then fill for a safe period of time, then measure, then repeat that
process. All sorts of possibilities with an intelligent controller like
the stamp. I think your limits are the strength of the "string" the weight
is on - and braided bronze wire is a possibility if necessary - and the
strength of the retrieval system.
Do be sure the wire can't jump the pulley though.
Jim H
>Hi,
>
> Wouldn't be worried about so many moving parts exposed to wear
>& weather? I would.
And who did you think was going to install a Stamp-based control circuit
and associated mechanicals exposed to the elements? Certainly no one smart
enough to actually make and program such a device. If I gotta include
every little obvious detail, shouldn't I get paid instead of doing this for
fun? Gimme a break! ;-)
Jim H
top
> I assume, you can be pretty sure that sonar and infrared will be totally
> useless because the air between top and surface of grain will be dense
with
> grain. If the weight is shaped appropriately, it can be pulled free,
> although this system isn't really meant to measure during a fast filling
> operation that could trap the weight beyond the ability to retrieve it.
(I
> had forgotten that.) You can include logic to stop filling ...
I wasn't thinking he wanted to measure while filling, just concerned about
burying the sensor.
For absolute positions at the top of dryers, bins, the bottom of hoppers,
etc. the industry uses a switch arrangenment that gives a contact closure
output (your choice of NO or NC) that measures whether a small vane is
being turned by a motor in the sensor. When the vane can't turn because of
the grain you've reached the trip point. If I remember correctly it's
called a "paddle switch". I ran across them working on the control systems
for some large tower style dryers a few years ago. They're kind of pricey.
Tim
>Has anyone used sonar to measure the distance of an object above
>water or other liquids? I need to measure a liquid level which will
>change from 3 to 10 feet.
>
>While I am asking, would sonar work with a granular surface? I want
>to measure the level of grain in a grain bin so there will be metal
>walls and ceiling reflecting signals around. Can I get enough echo
>off the grain without the signal bouncing around inside the bin
>messing things up?
>
>If so, how about infrared? Any ideas are welcome.
>
>Thanks in advance
Here are some switches intended for silo filling applications:
http://www.mix-uk.com/silodressings/indication.html
Regards,
Bruce Bates
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Didn't mean to give offense, which is why I phrased my comment
as a question. I was speaking from a *design* algorithm view.
Moving parts are a *bad* thing, to be avoided as much as
possible in devloping a solution to any measurement problem,
no?
Ken
with enough thrust, pigs fly just fine.
---- On Sat, 27 Oct 2001, Jim Higgins (HigginsJ@s...)
wrote:
> At 22:27 10/26/01, Ken Ambrose wrote:
>
> >Hi,
> >
> > Wouldn't be worried about so many moving parts exposed to
wear
> >& weather? I would.
>
> And who did you think was going to install a Stamp-based
control circuit
>
> and associated mechanicals exposed to the elements?
Certainly no one
> smart
> enough to actually make and program such a device. If I
gotta include
> every little obvious detail, shouldn't I get paid instead of
doing this
> for
> fun? Gimme a break! ;-)
>
>
> Jim H
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
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Subject
> and Body of the message will be ignored.
>
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>
>
>
>
writes:
> At 20:16 10/26/01, stujo wrote:
>
> Has anyone used sonar to measure the distance of an object above
> water or other liquids? I need to measure a liquid level which
> will change from 3 to 10 feet.
I have never used sonar.
You may also want to consider a using a pressure transducer. If the
liquid is water, one with a full-scale output at 120" of water or even 5
psi full-scale should work fine. (1 psi = 27.7" of water)
What is your price range?
>---- On Sat, 27 Oct 2001, Jim Higgins (HigginsJ@s...)
>wrote:
>
> > At 22:27 10/26/01, Ken Ambrose wrote:
> >
> > > Wouldn't be worried about so many moving parts exposed to
> > > wear & weather? I would.
> >
> > And who did you think was going to install a Stamp-based
> > control circuit
> > and associated mechanicals exposed to the elements?
> > Certainly no one smart enough to actually make and
> > program such a device. If I gotta include every little obvious
> > detail, shouldn't I get paid instead of doing this for
> > fun? Gimme a break! ;-)
>Didn't mean to give offense, which is why I phrased my comment
>as a question. I was speaking from a *design* algorithm view.
>Moving parts are a *bad* thing, to be avoided as much as
>possible in devloping a solution to any measurement problem,
>no?
I wasn't offended. I honestly thought you were kidding me by implying
that, moving parts or not, someone might leave a Stamp-based device exposed
to the weather just because I didn't remind them not to. I was responding
to that. I surely hope I didn't give offense either.
As for moving parts, the system principles I described are fairly commonly
used to obtain level measurements in bins and silos. The mechanicals are
about as simple as it gets when an actual measurement is needed vs just
knowing whether a certain point has been reached or not.
Where I used to work we went thru a number of "sophisticated" systems
involving:
1. An insulated wire strung from top to bottom inside a bin with
measurements taken by applying a small amount of RF to the wire and
measuring the change in reactance caused by the presence of product. This
required emptying the bin to determine the empty value, then filling to
100% to get the full point. But emptying the bin was impractical because
we needed to keep a healthy reserve of product and were running a 24/7
operation. It took two months after installing the system to get it
calibrated so it could be used, then a couple of months later the wire was
damaged (insulation melted) by an exothermic reaction when product
containing a trace of moisture got into the bin due to carelessness and the
system became useless.
2. Ultrasonic/sonar. Either the emitter or the sensor fouled with the
product and since it was an exceedingly dense product, about 8X water in
density, that system stopped working rather quickly.
3. After two "I told you so's" on my part, I was allowed to install a
turnkey (not home brewed) weighted pulley system and several years later it
was still operating. The earlier system had been of the same design and
had worked nearly 10 years trouble free.
The name comes to me now - see http://www.bindicator.com and look at their
Yo-Yo systems. They're about as simple and reliable as it gets for bin
filling applications, assuming the product isn't sticky. If the money is
available for a commercial solution, they're well worth contacting.
Jim H
question. How would infrared or sonar behave in such an environment?
Can infrared or sonar be focused to avoid the echo? I am not so
worried about sensing the level while filling the bin, just getting
readings afterwards. I fear dust would give false readings. Which
brings another thought, any mechanical switch would present a safety
question as grain dust is pretty explosive stuff under the right
conditions.
Without going into details I want to avoid any kind of 'float'
device. I also want to avoid having multiple devices per bin. If the
average farmer fred is to use such a device installation would have
to be fast and easy.
Thanks for all the ideas.
stujo
Hmm, very Interesting. I usually assume that measurement
techniques using mechanical methods can't compete for
reliability and accuracy with electronic technologies.
I would never have guessed that this problem would not yet
have been completely solved without the use of mechanical
devices. I stand corrected. [noparse]:)[/noparse]
Ken Ambrose
with enough thrust, pigs fly just fine.
---- On Sat, 27 Oct 2001, Jim Higgins (HigginsJ@s...)
wrote:
> At 15:08 10/27/01, Ken Ambrose wrote:
>
> >---- On Sat, 27 Oct 2001, Jim Higgins (HigginsJ@s...)
> >wrote:
> >
> > > At 22:27 10/26/01, Ken Ambrose wrote:
> > >
> > > > Wouldn't be worried about so many moving parts exposed
to
> > > > wear & weather? I would.
> > >
> > > And who did you think was going to install a Stamp-based
> > > control circuit
> > > and associated mechanicals exposed to the elements?
> > > Certainly no one smart enough to actually make and
> > > program such a device. If I gotta include every little
obvious
> > > detail, shouldn't I get paid instead of doing this for
> > > fun? Gimme a break! ;-)
>
> >Didn't mean to give offense, which is why I phrased my
comment
> >as a question. I was speaking from a *design* algorithm
view.
> >Moving parts are a *bad* thing, to be avoided as much as
> >possible in devloping a solution to any measurement problem,
> >no?
>
> I wasn't offended. I honestly thought you were kidding me by
implying
> that, moving parts or not, someone might leave a Stamp-based
device
> exposed
> to the weather just because I didn't remind them not to. I
was
> responding
> to that. I surely hope I didn't give offense either.
>
> As for moving parts, the system principles I described are
fairly
> commonly
> used to obtain level measurements in bins and silos. The
mechanicals
> are
> about as simple as it gets when an actual measurement is
needed vs just
> knowing whether a certain point has been reached or not.
>
> Where I used to work we went thru a number of "sophisticated"
systems
> involving:
>
> 1. An insulated wire strung from top to bottom inside a bin
with
> measurements taken by applying a small amount of RF to the
wire and
> measuring the change in reactance caused by the presence of
product.
> This
> required emptying the bin to determine the empty value, then
filling to
> 100% to get the full point. But emptying the bin was
impractical
> because
> we needed to keep a healthy reserve of product and were
running a 24/7
> operation. It took two months after installing the system to
get it
> calibrated so it could be used, then a couple of months later
the wire
> was
> damaged (insulation melted) by an exothermic reaction when
product
> containing a trace of moisture got into the bin due to
carelessness and
> the
> system became useless.
>
> 2. Ultrasonic/sonar. Either the emitter or the sensor
fouled with the
> product and since it was an exceedingly dense product, about
8X water in
>
> density, that system stopped working rather quickly.
>
> 3. After two "I told you so's" on my part, I was allowed to
install a
> turnkey (not home brewed) weighted pulley system and several
years later
> it
> was still operating. The earlier system had been of the same
design and
>
> had worked nearly 10 years trouble free.
>
> The name comes to me now - see http://www.bindicator.com and
look at
> their
> Yo-Yo systems. They're about as simple and reliable as it
gets for bin
> filling applications, assuming the product isn't sticky. If
the money
> is
> available for a commercial solution, they're well worth
contacting.
>
>
> Jim H
>
>
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Subject
> and Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
>
>
>
>
>Hmm, very Interesting. I usually assume that measurement
>techniques using mechanical methods can't compete for
>reliability and accuracy with electronic technologies.
Hi Ken,
Not necessarily for you, but for the possible benefit of those who plan a
career in engineering...
I often find higher tech solutions that offer improved precision of
measurements often can't be justified when the true needs for reliability
and accuracy are also considered. Sexy solutions often introduce needless
complexity that can come back to haunt you. It's a matter of taking
EVERYTHING into account before engineering a solution vs saying "How can I
do this with X" where X might be a Stamp, an ultrasonic ranging module, an
IR ranging module, etc, and then not deviating from this initial pick. We
have to scrupulously avoid the syndrome where the only tool we have is a
hammer so we must see every problem as a nail.
We can use a 555 IC and a few parts to produce a pulse approximately every
2 seconds, or we can use a Stamp and a real time clock/timer module to
produce one every 2.000 seconds. Which is better? It depends on the level
of the need for accuracy and precision.
For a silly example - we might stop fights among siblings over the size of
dessert portions by using a precision balance to divide a portion of banana
pudding so that the two children get the same portion within 0.01
grams. But why would we want to do that when they can't see a difference
of 5 - 10 grams? And would they still fight if they thought one got more
bananas, or more vanilla wafers even though the weight was equal? The
balance isn't a good solution.
In a huge bin, do we really need to resolve the fill level closer than an
inch or two? In some cases, maybe we do. In a grain bin? I doubt it. If
we adopt a system that gives excellent precision of measurements, what
about accuracy? Materials tend to cone up a bit during filling, and cone
down during emptying - more or less depending on the angle of repose of the
material in question. What use is a measurement system that resolves depth
to 0.05 inches when the "errors" introduced by coning make it impossible to
pick a point of measurement that justifies reporting a value to 0.05
inches. Which is more useful, a measurement of 123.45 +/- 1.5 inches, or a
measurement of 123 +/- 1.5 inches? Both have some risk if the material
cones up 3 feet during fill and down 3 feet during draining. So we weigh
the need for accuracy, decide to measure halfway from center to edge,
realizing Production can live with 10% increments and the
inventory/accounting types are thrilled with 2% since they only care about
measuring the tank twice a year during inventory and they don't care if one
measurement is off by 2% when the tank has been filled and drained 75 times
since and they know to within a thousand pounds or so the weight of
everything that ever went into that 80 ton capacity bin over the last half
year.
And none of this takes into account the sexy system costing $3500 and
needing corrective maintenance twice a month, or preventive maintenance
weekly, while the low tech approach costs $1800 and only requires
significant attention 10 years later. (I made up the price comparison
because I forgot the real prices.)
A really neat $olution is to put the bin on load cells to measure weight
directly, no error from coning, but now how do we periodically verify
calibration? I'm pretty sure a stepper motor that raises and lowers a
weight turns the same amount per pulse ten years from now as it does
today. I'm pretty sure the tank height and diameter don't change. I don't
want to be called (sometimes at 2:30 am) every time the ultrasonic or
infrared devices get fouled and have to tell maintenance to clean them like
they did two weeks ago, and two weeks before that, and two weeks before
that... and fight with the Production Manger over the repeated down time
for maintenance, or for twice yearly calibrations requiring emptying the
tank to establish zero and hanging a few tons of calibrated weights on the
tank to verify span... and with the Maintenance Manager over why his people
can't remember what they had to do to solve an identical problem every two
weeks for the last six months and besides why in hell doesn't he just put
the damn thing on a 7-day PM schedule when they shut down for 4 hours on
Sunday... and it was *his* boss, the Plant Engineer (who's not really an
engineer) who selected the fancy system over my objections so leave me the
heck alone until he is ready to take up my cause to replace the system with
a Yo-Yo.
It isn't always this bad, but this is the real world the things we engineer
must work in.
Jim H
really an engineer), you said it there. I have found that much are
educated idiot's that can not find there own hole to Smile out of.
And I truley agree with this quote that I took from you below. But
first all let me tell you a little about my credentials first.
My name is Timothy Hosey and I work for Cardinal Packaging a
subsidary of Berry Plastics. We are one of around 14 plants in the
U.S. and two overseas that produce containers, drink cups and
household plastics items. I am a certified Electrician with the
State of Ohio, a Journeyman Industrial Electrician with the State of
Ohio, a two year electronics tech from the U.S. Navy (Nuculear
Submarine School), Certification in Refrigeration with Stark Tech U.,
Certified Allen Bradley Advanced Programmer, listed with Microsoft
Corp as an industrial Programmer, do alot of rebuilding of Machinery
and Robotics in the Industrial Env., as well as play with Basic
Stamps and SX chips as a hobby in my spare time. I have been with
Cardinal for 6 years and now presently work for them as an
Engineering Tech. I have seen Engineers, I mean managers come and
go. That being said here is my opinion.
If someone is trying to produce somthing for industy with little
experience, then don't do it. Plain and simple, do not do it. Buy a
yo-yo from Bindicator. Now if someone is doing this for fun or for
there own farm then go ahead. But like Jim said you will be the one
held ultimatly responsible and I have been there it is not good.
Trust me on this one.
I have 9 silos for plastic resin, and currently we are using a
bindicator yo-yo system. It was a great accomplishment 15 year old
Technology. It works like a mouse, with a string and plastic weight
and a spining disk that sends pulses to a processor. I even used a
plc to capture the pulses with a little math and an ethernet card so
we wouldn't have to go back and push the little button. The down
falls of the system are as follows:
1. You can't measure while filling.
2. It takes forever on our 40 + foot silos if they are almost empty
to get a measurment.
3. The bottle bust's from the cold. Winter is a Smile poor time to
have to climb to replace.
4. The twin is always getting tangled up. See above on Winter
5. It always comes to rest as the photo eye is being blocked by the
wheel. This will not allow for any others to be read since they are
multi-plexed.
Well as you can see my team has had it with the yo-yo. The first 8
years the system worked very well. Now the mechanicals are wearing
out it is time to replace.
I have looked at sonic sensing. Especially "see above" since I was
on a Nuc Sub and was a Sonar Tech. I absoulutly love the Hydepark
Sonic sensor for alot of applications that I can't do with a regular
optical one. But there are problems with it. Echoing in a small
vessel along with dust and angle hair streamers from plastic. We
have also looked at RF but same thing with this as sonic. I even
thought about load cells. How the heck am I going to put them under
a 40 ft by 9' diameter silo. But this would be the most effective
method. Since all of the above will only give you a plus or minus ft
resolution. Yes even the yo-yo. The reason is that when filling you
will measure the up sweep and when it starts pulling to the cone you
measure the down sweep. You try to put the aparatus half way between
the side and the center to accomodate this.
Now to what we are doing to actually make some sense. Oh by the way
bindicator offers the sonic, rf, as well as the yo-yo as well as what
we are going with. The phase tracker. This device sends to wires
down to the bottom and is permanetly weighted down there. The system
is made to order and for our 9 silos is going to run just under
$20k. The yo-yo and the rest are about the same in price as this
also. And one of our sister plants is installed with the sonic
sensors from bindicator. This system is constantly in contact with
the material and sends a 4-20 ma signal back to a display. I opted
for the analog expansion cards so now I am building an Ethernet SX
web server. Yes a web server on an sx card available from Ubicom the
makers of the sx chip. We will be installing in a month or two.
I hope this helps out for the person who wanted to build it
themselves. Like I said if it is for a large industry then don't.
If it is for a Mom and Pop or farm then knox yourself out.
Statement: This is just my opinion and I don't wish to get in a
fighting match over it. Just please beware if you intend to build
this yourself.
And yes pigs will fly with enough force behind them.
Good luck,
Timothy Hosey
Engineering Tech
P.S. Jim Below is quite true. Good Statements
I don't want to be called (sometimes at 2:30 am) every time the
ultrasonic or infrared devices get fouled and have to tell
maintenance to clean them like they did two weeks ago, and two weeks
before that, and two weeks before that... and fight with the
Production Manger over the repeated down time for maintenance, or for
twice yearly calibrations requiring emptying the tank to establish
zero and hanging a few tons of calibrated weights on the tank to
verify span... and with the Maintenance Manager over why his people
can't remember what they had to do to solve an identical problem
every two weeks for the last six months and besides why in hell
doesn't he just put the damn thing on a 7-day PM schedule when they
shut down for 4 hours on Sunday... and it was *his* boss, the Plant
Engineer (who's not really an engineer) who selected the fancy system
over my objections so leave me the heck alone until he is ready to
take up my cause to replace the system with a Yo-Yo.
>water or other liquids? I need to measure a liquid level which will
>change from 3 to 10 feet.
I'm tuning in late on this interesting thread. I have experience with Lundahl
<http://www.automationsensors.com/> ultrasonic sensors for water
level monitoring. They are great when the liquid is calm, in a tank
or stilling well.
However, they are not satisfactory when the surface is not square
with the sensor or when the water surface is agitated. The sensor
either comes back with a false lock or never locks at all. We were
trying to monitor small streams that would swell tremendously after a
rainstorm. Stilling well not an option. Big change in slope of the
water surface and agitation.
I can't imagine how they could perform decently in a grain silo,
given the other comments in this thread.
-- regards,
Tracy Allen
electronically monitored ecosystems
mailto:tracy@e...
http://www.emesystems.com
Your example of sibling fights over portions has a human factors engineering
solution, that I learned long ago in late night study sessions as an
undergrad physics major: when the pizza arrived, person A would cut it in
half, and person B would get first choice on which half.
Dennis
Original Message
From: "Jim Higgins" <HigginsJ@s...>
To: <basicstamps@yahoogroups.com>
Sent: Sunday, October 28, 2001 9:08 AM
Subject: Re: Re: [noparse][[/noparse]basicstamps] sonar measurements
<deleted>
.> For a silly example - we might stop fights among siblings over the size
of
> dessert portions by using a precision balance to divide a portion of
banana
> pudding so that the two children get the same portion within 0.01
> grams. But why would we want to do that when they can't see a difference
> of 5 - 10 grams? And would they still fight if they thought one got more
> bananas, or more vanilla wafers even though the weight was equal? The
> balance isn't a good solution.
<deleted
make sure you have some way of keeping the water off the sonar
transducer. As for the grain, that is a pretty dusty environment so
you may have to encase the transducer in something with a very
thin sheet of plastic as close to the transducer as you can get
without touching it. This may reduce the range so experimentation
is in order here. I would try putting the transducer in a tuna can
with felt glued to the inside and saran wrap over the open side with
the transducer mounted inside facing out right behind the plastic
wrap 'window'. This will occasionally need 'dusting off' as dust will
collect on the plastic film. To fix this, you could mount one of
those small vibrating motors like you find in toys or some electric
vibrating toothbrushes. Tell your microcontroller to periodically
'dust' the sonar by vibrating the unit for a few seconds.
Doug
P.S. I'm working on similar operations for poultry operations here
southwest Arkansas
On 27 Oct 2001, at 0:16, stujo wrote:
> Has anyone used sonar to measure the distance of an object above water
> or other liquids? I need to measure a liquid level which will change
> from 3 to 10 feet.
>
> While I am asking, would sonar work with a granular surface? I want to
> measure the level of grain in a grain bin so there will be metal walls
> and ceiling reflecting signals around. Can I get enough echo off the
> grain without the signal bouncing around inside the bin messing things
> up?
>
> If so, how about infrared? Any ideas are welcome.
>
> Thanks in advance
>
>
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Doug
On 26 Oct 2001, at 22:02, Jim Higgins wrote:
> At 20:16 10/26/01, stujo wrote:
>
> >Has anyone used sonar to measure the distance of an object above
> >water or other liquids? I need to measure a liquid level which will
> >change from 3 to 10 feet.
> >
> >While I am asking, would sonar work with a granular surface? I want
> >to measure the level of grain in a grain bin so there will be metal
> >walls and ceiling reflecting signals around. Can I get enough echo
> >off the grain without the signal bouncing around inside the bin
> >messing things up?
> >
> >If so, how about infrared? Any ideas are welcome.
>
> Hang a small weight over a pulley attached to a micro switch so the
> weight trips the micro switch. From the home position, lower the
> weight until the switch "untrips" because the weight is no longer
> supported; i.e., has come to rest on the grain. Count pulses to a
> stepper motor needed to achieve this result and convert to depth.
> Retract weigh to home position until next measurement is needed.
> Properly done the whole mechanism can be outside the silo with only a
> tiny hole for the line. The weight stays inside. Steel weight, not
> lead since grain is edible. You can assure proper home position by
> tripping a second micro switch that needs more weight/resistance to
> trip so when the weight retracts against the top of the tank this
> switch tells the controller to stop retracting. Trip weights are set
> using springs with different tensions. Simple, non fouling, very low
> maintenance, essentially foolproof calibration.
>
>
> Jim H
>
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the grain as it fills the hopper. . .
On 26 Oct 2001, at 21:31, Tim McDonough wrote:
> > Hang a small weight over a pulley attached to a micro switch so the
> weight
> > trips the micro switch. From the home position, lower the weight
> > until
> the
> > switch "untrips" because the weight is no longer supported; i.e.,
> > has
> come ...
>
> Interesting idea. Sometimes grain bins fill pretty rapidly. If the
> weight were buried the system might not be able to easily pull it free
> from the grain.
>
> Tim
>
>
>
>
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