micro force sensor or transducer

On 3 Jan 2007 10:00:08 -0800, "shehab.albahri@gmail.com"


What is that in grams?

Paul M wrote:

1 micro newton is 0.0001019716 gram force.

Paul M wrote:

If you're being picky, it's meaningless.  One Newton of force will
accelerate one gram of mass at 1000 meters/second.  Since the
acceleration due to gravity at the earth's surface is about 9.8m/s, you
can invent a 'gram force' and define it as the force exerted by a gram
of mass at the earth's surface -- but why not use the accepted unit?

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google?  See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html

gUqv6tQDYnZ2dnUVZ_vOlnZ2d@web-ster.com:


If you're being super picky, that would be 9.8 m/s/s!

--
Scott
Reverse name to reply

Tim Wescott wrote:

   ...


If you're being picky, it's 1000 meters/second/second. :-)


Because I don't go to the deli and buy a 5 Newtons of cheese. The
attendant measures out kilos by a process called "weighing".

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

Jerry Avins wrote:


Oy!  I've been a jerk (m/s^3).


Hopefully the scale is placarded as to the need for recalibration if
it's used on another planet.

Older scales, even cheap ones, often used a weight-balance principal,
which (barring issues of friction &c) would have measured mass in any
uniformly accelerated frame of reference.

I think all the new ones use force sensors, and depend on the
acceleration of gravity, which as any schoolchild knows is one slug per
pound.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google?  See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html

Tim Wescott wrote:

   ...


Ugh! Mighty big slugs! I've seen shrimp for sale at 3 per pound, and
even they were huge.

I'm partial to poundals, myself.

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

I am glad you having fun at this post, guys this is really important
and if any one has any ideas I will be more than glad to share it with
him .
the application I am working at right now is a simple nano-indentation
machine , the indenter applies micro force on the sample that I am
testing . I am applying this force using a nano linear stage,
unfortunately the input parameter for the linear stage is displacement
but the stage is connected to a controller so if I can measure the load
applied when the linear stage moves I will be able to do some kind of
closed loop feed back system so I can control the movement of the
linear stage. so basically what I am saying the sensor or the
transducer should be able to be connected to moving structure , thanks
again and appreciate your help .
1 micro Newton = 0.1 milligram force assuming a=10 m/s^2

Jerry Avins wrote:

¯AF¯AF¯AF¯AF¯AF¯AF¯AF¯AF¯AF¯AF¯AF

shehab.albahri@gmail.com wrote:

I hope you don't feel that the fun is at your expense. I also hope you
know that if we had anything of value to contribute, we would have done
that already. There must be devices that can measure 100 micrograms, but
I don't know what they are.

Some of the readers here are good inventors. What are your size constraints?

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

I've done my best by pointing you to Akers and suggesting a construction
if you need to make one.  That's usenet for you.  The chaff's OK, so long
as the wheat is someplace.

--
Scott
Reverse name to reply

shehab.albahri@gmail.com wrote:
(top posting fixed)


We _are_ having fun with this, but as Jerry mentioned we're not really
answering your question because we're stumped.

You're probably stuck with building your own, more's the pity.  The only
two ways that I can think of, off hand, to build a force sensor is to
(a) take something with a know spring constant and measure its
deflection, or (b) take something that generates a known force from a
known input, servo its deflection to zero, and measure the input.

If your linear stage is friction free you may be able to use the latter
method by monitoring its drive when you're just holding it up vs. when
you're pushing down.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google?  See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html

proclaimed to the world:


From what he added, you can eliminate A being ok, which was what I
suggested without know the requirements. If this is nanoscale, then
the deflection necessary to measure force will be too great for the
process. A tiny strain gauge element attached to the device he is
using might work. I would just have to know more or see the
application to offer anything feasible.

proclaimed to the world:


That is cute. Let's see, what is s^4 called? Yank?

proclaimed to the world:


Jerry is correct here. I needed a familiar scale so I could get an
idea of how much force that was. I understand the difference between
force and weight.

Having an idea of scale now (I figured it was small), I can visualize
ways of building a sensor. I don't know how unusual it is to be
measuring something of this scale.

If nothing off the shelf is available, you can often make something
that will work by making something sensitive enough to produce a
motion large enough so that the motion can be measured with something
off the shelf. For instance I could use some taut band stock used in
meter movements, pulled tight in a frame and attach a balanced arm. I
then could measure the movement of the arm when a very small force is
applied using a capacitance prox sensor. Another approach would be
using a strain gauge glued to some sort of taut band configuration.

But I don't have enough information to know if this is feasible to the
OP, what his requirements are, etc. I'm just doing mental exercise. I
could have looked up the conversion, I most likely have a calculator
with that conversion on the computer I am sitting at, I was being lazy
in some ways. I just thought the OP might know it off the top of his
head.

Back in the day, I made a transducer at the nanoNewton scale to measure
force from one cardiac fiber at a time.  The design theory (which I
certainly can't claim credit for) was to butt the square ends of two optic
fibers together, loop the muscle fiber around the free end of one fiber in
a u-shaped using pulled capillary tubes, and measuring the light that
passed from one fiber to the next while the fiber twitched.  Different
diameter optic fibers would provide different moduli.

The smallest off-the-shelf strain gauge I can remember is the Akers AE801,
but I can't find hide nor hair of Akers online.  I don't know if they still
exist

--
Scott
Reverse name to reply

Five or ten years ago "Scientific American" mag. in the "Amateur
Scientist" section had a project on measuring the "heartbeat" (or
whatever) rate of a flea. The flea was glued to the end of a small
"beam" and  a strain gage on the beam measured the stick deflections
caused by the heartbeats. A small op-amp cct. was also required.

Could someone lookup the issue to help the OP ?
.
.
.
.

Feb 1966 page 120 has a cct for the electrocardiogram of a flea. Maybe
it is the one?

Yikes!   40 years ago!