Anybody here know about strain gauges and the like?

If you do maybe you can give me some guidance. I would like to be able
to measure the torque required to drive taps so that I know when the
tap is getting dull. The torque range is from .5 to 106 inch lbs. The
sensor needs to be very low power and the sensor/reader package needs
to cost less than $100.00. Is this possible? I am thinking about a
MEMS sensor that is powered like an RFID so that there is no contact.
The signal from the sensor will then be sent by radio to a receiver
less than 15 feet away. I have been looking online but haven't yet
found what I'm looking for.
Thanks,
Eric

 

[Jasen Betts]

On 2014-12-10, etpm@whidbey.com <etpm@whidbey.com> wrote:

If you do maybe you can give me some guidance. I would like to be able
to measure the torque required to drive taps so that I know when the
tap is getting dull. The torque range is from .5 to 106 inch lbs. The
sensor needs to be very low power and the sensor/reader package needs
to cost less than $100.00. Is this possible? I am thinking about a
MEMS sensor that is powered like an RFID so that there is no contact.
The signal from the sensor will then be sent by radio to a receiver
less than 15 feet away.

for $100 you'll get about 4" range in passive RFID

forget MEMS, strain gauges are not microscopic.


--
umop apisdn

 

[Bob Masta]

On Wed, 10 Dec 2014 09:47:37 -0800, etpm@whidbey.com wrote:

If you do maybe you can give me some guidance. I would like to be able
to measure the torque required to drive taps so that I know when the
tap is getting dull. The torque range is from .5 to 106 inch lbs. The
sensor needs to be very low power and the sensor/reader package needs
to cost less than $100.00. Is this possible? I am thinking about a
MEMS sensor that is powered like an RFID so that there is no contact.
The signal from the sensor will then be sent by radio to a receiver
less than 15 feet away. I have been looking online but haven't yet
found what I'm looking for.
Thanks,
Eric

It's been decades since I used strain gages, but I suspect
the basics are still true. At the most elemental level you
have naked strain gages (or whatever technology) that have
to be bonded to the part you are applying the torque or load
to, then calibrated. Big PITA.

Then you have ready-made sensors that have the strain gages
already bonded to a nice torque- or load-sensing structure,
with raw bridge outputs, or with built-in electronics. The
latter is surely what you want.

The issue becomes whether you can find a ready-made type
that you can easily incorporate into your setup... it need
to handle the right torque range, of course, but it also
needs to physically fit and be easy to couple between the
driver and tap.

Sometimes the attachment issue can overshadow everything,
forcing you to revert to bonding raw gages to
strangely-shaped parts. But I suspect in your case you will
be able to find a ready-made sensor.

Have you considered some sort of "proxy" method, such as
measuring drive motor current? I'm guessing that you don't
really need torque measurement as such, just some
corresponding thing that you can detect when it goes above
some threshold.

Best regards,


Bob Masta

DAQARTA v7.60
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, Pitch Track, Pitch-to-MIDI
FREE Signal Generator, DaqMusiq generator
Science with your sound card!

 

[RobertMacy]

On Thu, 11 Dec 2014 06:22:12 -0700, Bob Masta <N0Spam@daqarta.com> wrote:

...snip...
Have you considered some sort of "proxy" method, such as
measuring drive motor current? I'm guessing that you don't
really need torque measurement as such, just some
corresponding thing that you can detect when it goes above
some threshold.

Best regards,


Bob Masta
DAQARTA v7.60
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, Pitch Track, Pitch-to-MIDI
FREE Signal Generator, DaqMusiq generator
Science with your sound card!

Current's not bad idea at all.

When first confronted with this problem, I envisioned a torque measuring
shaft wih sometype of vernier scale you could view, then synchronously
'flash' the optics to look at the vernier scale as it rotates during use.
Manual reading not electronic, but simple - maybe.

The other technique was again to use shaft torque angle displacement, use
YOUR soundcard software to drive a rotating coupled transformer winding in
top, pick up the small angular offset to phase sensitive winding in
'bottom' and pick that up wirelessly too. That is four independent
windings in all.

But measure current? Never occurred to me. Worst part of this is that
back in the 70's we had this problem with dullin milling bits, and the
solution, yes measure the current! Actually power, but same principle. oh
how quickly we forgeet.

 

[Jim Thompson]

On Thu, 11 Dec 2014 08:45:21 -0700, RobertMacy
<robert.a.macy@gmail.com> wrote:

On Thu, 11 Dec 2014 06:22:12 -0700, Bob Masta <N0Spam@daqarta.com> wrote:

...snip...
Have you considered some sort of "proxy" method, such as
measuring drive motor current? I'm guessing that you don't
really need torque measurement as such, just some
corresponding thing that you can detect when it goes above
some threshold.

Best regards,


Bob Masta
DAQARTA v7.60
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, Pitch Track, Pitch-to-MIDI
FREE Signal Generator, DaqMusiq generator
Science with your sound card!

Current's not bad idea at all.

When first confronted with this problem, I envisioned a torque measuring
shaft wih sometype of vernier scale you could view, then synchronously
'flash' the optics to look at the vernier scale as it rotates during use.
Manual reading not electronic, but simple - maybe.

The other technique was again to use shaft torque angle displacement, use
YOUR soundcard software to drive a rotating coupled transformer winding in
top, pick up the small angular offset to phase sensitive winding in
'bottom' and pick that up wirelessly too. That is four independent
windings in all.

But measure current? Never occurred to me. Worst part of this is that
back in the 70's we had this problem with dullin milling bits, and the
solution, yes measure the current! Actually power, but same principle. oh
how quickly we forgeet.

You no longer need to think... just use a microprocessor >:-}

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[whit3rd]

On Wednesday, December 10, 2014 9:47:02 AM UTC-8, et...@whidbey.com wrote:

If you do maybe you can give me some guidance. I would like to be able
to measure the torque required to drive taps so that I know when the
tap is getting dull.

If you chuck the tap in a battery drill/driver, you can just adjust the torque
limit, so a dull tap 'clicks' instead of rotating. Or, you could put a torque-limit
screwdriver mechanism in a suitable tapping jig. The downside, is that
most drill/driver mechanisms will jerk your hand sideways (and break
the tap).

A straight-cylinder battery torque-limiting drill would be perfect (you'd still have the
feel of the torque, and could let the cylinder slip in your hand instead
of snapping the tap). Alas, I don't know of any such.

 

[RobertMacy]

On Thu, 11 Dec 2014 09:27:47 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@on-my-web-site.com> wrote:

...snip....

You no longer need to think... just use a microprocessor >:-}

...Jim Thompson

Took me a while to get used to replacing $20 worth of analog parts with $1
PIC, or $5 FPGA that to add insult to injury actually would outperform the
analoog design.

 

[Tim Wescott]

On Thu, 11 Dec 2014 09:27:47 -0700, Jim Thompson wrote:

On Thu, 11 Dec 2014 08:45:21 -0700, RobertMacy <robert.a.macy@gmail.com
wrote:

On Thu, 11 Dec 2014 06:22:12 -0700, Bob Masta <N0Spam@daqarta.com
wrote:

...snip...
Have you considered some sort of "proxy" method, such as measuring
drive motor current? I'm guessing that you don't really need torque
measurement as such, just some corresponding thing that you can detect
when it goes above some threshold.

Best regards,


Bob Masta
DAQARTA v7.60
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, Pitch Track, Pitch-to-MIDI
FREE Signal Generator, DaqMusiq generator
Science with your sound card!

Current's not bad idea at all.

When first confronted with this problem, I envisioned a torque measuring
shaft wih sometype of vernier scale you could view, then synchronously
'flash' the optics to look at the vernier scale as it rotates during
use. Manual reading not electronic, but simple - maybe.

The other technique was again to use shaft torque angle displacement,
use YOUR soundcard software to drive a rotating coupled transformer
winding in top, pick up the small angular offset to phase sensitive
winding in 'bottom' and pick that up wirelessly too. That is four
independent windings in all.

But measure current? Never occurred to me. Worst part of this is that
back in the 70's we had this problem with dullin milling bits, and the
solution, yes measure the current! Actually power, but same principle.
oh how quickly we forgeet.

You no longer need to think... just use a microprocessor >:-}

Trust me on this Jim -- you still have to think.

The biggest problem in using a microprocessor where an analog circuit can
do the job, is that the guy designing the system -- circuitry AND code --
needs to understand analog electronics. If it's going to work well, the
microprocessor just becomes a custom analog component. Not everyone can
do that.

--
www.wescottdesign.com