Strain gauges or load cells cheap/homebrew

Does "more or less" mean anything at all to you?

Jim



Rene Tschaggelar <none@none.net>
shared these priceless pearls of wisdom:

being
->> weighed (an automobile, actually) and all support more or less an equal part
of
->> the weight.
->>
-> No. Your 4 point's won't have the same force.
-> Think again. The 4 wheels won't have the same force either

..
 
More time than money is always the case in my endeavors. Thanks for the links.

Jim




Gary Peek <mylastname@mycompanyname.com>
shared these priceless pearls of wisdom:


->
->Jim, Assuming you have more time than money, you may want
->to make your own load link, which means gluing strain gauges
->onto some metal piece than stretches.
->
->See our resource page:
->Collecting Parachute Test Drop Data
->at http://www.industrologic.com/cptdd.htm
->The link: Constructing your own load links
->shows how it can be done.
->
->Our SGAMP-2 may be what you need to amplify it too.
 
Roger...

I learned a LONG time ago to use the term "vehicle" or "automobile" instead of
"airplane". If you think the number of idiotic replies I got that didn't speak
to the subject matter in the least about "automobiles" were a lot, you can't
imagine the "experts" out there that know all about aircraft law and regulation
because their granddaddy upchucked his lunch one day when the barnstormers came
through town.

Yeah, it's an aircraft application, but I don't have the latitude to assume that
somebody down the road from the folks I'm trying to help have scales in their
garages.

Jim



"Roger Hamlett" <rogerspamignored@ttelmah.demon.co.uk>
shared these priceless pearls of wisdom:

->I suspect Jim, might be wanting to weigh an aeroplane. I looked a while ago
->at building a simple system based on the designs in the home scales to do
->this. At heart it is not difficult, provided you return a simple 'number'
->from the strain gauge, and then calibrate with a known load, at the same
->temperature.
 
Excellent reply, and I thank you kindly.

Jim


Dan Major <nospam@this.address>
shared these priceless pearls of wisdom:


Get ahold of either the
->folks at Omega (www.omega.com) or Vishay Micromeasurements
->(http://www.vishay.com/brands/measurements_group/guide/guide.htm). Both
->sell strain gages for making up your own load cells. Both will provide you
->with written references on how to calculate the physical properties (sizes)
->of your load cells. Another reference book I would recomend is Beckwith
->and Buck "Mechanical Measurements". If you're still having problems after
->contacting thtese folks, post back.
 
I read in sci.electronics.design that Roger Hamlett <rogerspamignored@tt
elmah.demon.co.uk> wrote (in <7C%7c.677$Gr.111@newsfe3-win.server.ntli.n
et>) about 'Strain gauges or load cells cheap/homebrew', on Tue, 23 Mar
2004:
I suspect Jim, might be wanting to weigh an aeroplane.
Click to expand...
Aeroplanes don't weigh anything. How could they float if they did?
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
 
On Fri, 26 Mar 2004 21:49:11 -0800, the renowned Jim Weir
<jim@rst-engr.com> wrote:

The question was not how to machine the bending arms or how low a level the
signal was. The question was how to make or buy strain gauges for little money.
RTFQ.

The title (above) does mentions load cells. You also gave not the
Click to expand...
slightest clue as to what *you* considered expensive. Learn to ask the
FQ better for better FA.

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
 
One of the good things about a newsgroup is that people give their time to
answer questions from other posters. It is a great resource even if some of
the answers don't always address the questin precisely - they are thanswers
that ca often trigger some new thinking, warn of possible problems or simlpy
give some advice related to the question.

Isn't it a shame then, that Jim Wier sees fit to write no less than 8
replies similar to this one to berate those people who offered their
experience to him simply because they didn't answer his question precisely
enough for his liking. I am sure all of those he criticised will be
thinking very carefully before they answer another question from Jim - in
case they get the 'wrong answer' again.


"Jim Weir" <jim@rst-engr.com> wrote in message
news:sa5a6052c951uglhfgro2nd58hdvgaordu@4ax.com...
The question was not how to machine the bending arms or how low a level
the
signal was. The question was how to make or buy strain gauges for little
money.
RTFQ.


Jim




Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat
shared these priceless pearls of wisdom:

-
->Well, strain gauges are cheap (maybe 5 dollars each). You can always
->have at it and try machining your own bending arms (don't forget
->mechanical overload protection) and attach the strain guages to them.
->The output is pretty low level as well for such a wide ambient range
->(you're looking for 50 microvolts accuracy, give or take). Good luck
->with it.
-
->Best regards,
->Spehro Pefhany
Click to expand...
 
"Jim Weir" <jim@rst-engr.com> wrote in message
news:806a60hh4r0luq2hgbprktt1j1kjou76tq@4ax.com...
Roger...

I learned a LONG time ago to use the term "vehicle" or "automobile"
instead of
"airplane". If you think the number of idiotic replies I got that didn't
speak
to the subject matter in the least about "automobiles" were a lot, you
can't
imagine the "experts" out there that know all about aircraft law and
regulation
because their granddaddy upchucked his lunch one day when the barnstormers
came
through town.

Yeah, it's an aircraft application, but I don't have the latitude to
assume that
somebody down the road from the folks I'm trying to help have scales in
their
garages.

Jim
Classic problem.
Click to expand...
The strain gauge sensors are dirt cheap then. If you cannot find a US
supplier who sells in small quantities, RS components in the UK do them, and
will send to th US for a credit card order. Schools also often used to get
the elements, and glue them onto a bit of bar, to show strain as part of the
physics syllabus over here. Think in terms of allways using them in pairs,
with the two sensors on opposite sides of a Wheatstone bridge configuration.
These are about Ł3.50, in 'one off' quantities.
The 'care', will involve designing something to avoid overstraining the
sensors, but given your ability to calibrate with a load similar to the
required 'target', and presumably to do the calibration at a similar
temperature, most of the nasty factors that make things complex, can be
largely avoided. :)
If you cannot source the sensors in the US easily, I can send a few over.

Good Luck.

"Roger Hamlett" <rogerspamignored@ttelmah.demon.co.uk
shared these priceless pearls of wisdom:

->I suspect Jim, might be wanting to weigh an aeroplane. I looked a while
ago
->at building a simple system based on the designs in the home scales to
do
->this. At heart it is not difficult, provided you return a simple
'number'
->from the strain gauge, and then calibrate with a known load, at the same
->temperature.
Click to expand...
 
Jim Weir wrote:
And having done special low-noise, low-drift, and high gain electronics damn
near all my 45 year professional career, I think I can handle the electronics.
The question was how to make or buy a cheap strain gauge.

Jim
Click to expand...
Difficult assertion to believe considering you were too damned stupid to
even look at Omega.
 
"Pat Ford" <pat.ford@nrc.ca> wrote in message
news:c3s7bn$d26$1@nrc-news.nrc.ca...
"The Real Andy" <i_luv_beer_especially_pilsners@yahoo.com.au> wrote in
message news:40616162@dnews.tpgi.com.au...
"Rene Tschaggelar" <none@none.net> wrote in message
news:4060b6f5$0$701$5402220f@news.sunrise.ch...
Jim Weir wrote:
I have a one-off application where I need to measure weights in the
1500-3000
pound (600-1500 kg) range. There are four points of support on the
item
being
weighed (an automobile, actually) and all support more or less an
equal
part of
the weight.

No. Your 4 point's won't have the same force.
Think again. The 4 wheels won't have the same force either.

The 4 points may well be different, but sum them up and you will get a
single weight of the item you are weighing. No platform is required. In
fact, using 3-4 single 'weigh pads' is fairly typical when weighing
aircraft
and vehicle.

The 4 points will be different and that is probly why he wants to weigh
the
car. Changing the cg is a common method of tuning a chasis, and knowing
where the cg is requires the 4 weights at the wheels. Brake tunning is
affected by cg height as well so what I'd do is have the 4 scales on a
platform so you can lock the suspension, and tilt the car. The cg height
is
then figured out using trig, after you see where the apparent cg moved.
Click to expand...
Hence the reason for using seperate weigh pads in racing and aeronautical
environments.

Pat

ps I used 4 bathroom scales and reworked the springs, I didn't care about
accuracy as much as repeatability
Click to expand...
for cg i guess it doesn't matter to much
 
My Human Politeness Strain Gauge just tripped and hit the BOZO BIN
button for this guy.
--
Regards, Terry King ...In The Woods In Vermont
terry@fredking.us
The one who Dies With The Most Parts LOSES!! What do you need?
 
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