Display Changes in Resistance caused by stretching a conduct

[gilak]

I wonder whether someone could please help me in devising or buying a
system for displaying changes in resistance caused by stretching a
conductive material. I have got the material and able to measure the
changes in resistance using an ohm meter. I am a computer programmer
but know nothing about electronics. Ideally I want to be able to read
data via USB port and then develop my own program to display the
changes. Any help on this will be appreciated.

 

[Rich Webb]

On Thu, 5 Apr 2012 08:12:03 -0700 (PDT), gilak <bkasmai@gmail.com>
wrote:

I wonder whether someone could please help me in devising or buying a
system for displaying changes in resistance caused by stretching a
conductive material. I have got the material and able to measure the
changes in resistance using an ohm meter. I am a computer programmer
but know nothing about electronics. Ideally I want to be able to read
data via USB port and then develop my own program to display the
changes. Any help on this will be appreciated.

The simplest way to start would be to use a USB data logger. Connect the
conductive material and one other resistor in a "voltage divider"
configuration, and measure the voltage from the junction between the
two, referenced to ground. Then do the math to work backwards to the
resistance.

<http://www.mccdaq.com/usb-data-acquisition/USB-1208-Series.aspx> is one
option. It includes a basic data logging application as well as the
necessary DLLs for you to write a more sophisticated app, if desired.
The presence of (controllable) analog outs as well as a 5V output would
make your project pretty easy, requiring just this pod plus a resistor
and a little software.

http://www.dataq.com/usb-data-acquisition/usb-data-acquisition.html is
another popular source. I don't think they're as flexible as the MCC
pods but they are an option.

--
Rich Webb Norfolk, VA

 

[Randy Day]

In article <caf6127f-347d-4980-b466-
a69b156e524a@l7g2000vbw.googlegroups.com>, bkasmai@gmail.com says...

[snip]

but know nothing about electronics. Ideally I want to be able to read
data via USB port and then develop my own program to display the
changes. Any help on this will be appreciated.

Are you looking for a pre-built test instrument
to measure this, or do you want to design a
circuit as part of a product?

There are hand-held oscilloscope models with
DVM functions and USB connectivity, but
they're not cheap.

 

[Tim Wescott]

On Thu, 05 Apr 2012 11:33:37 -0400, Rich Webb wrote:

On Thu, 5 Apr 2012 08:12:03 -0700 (PDT), gilak <bkasmai@gmail.com
wrote:

I wonder whether someone could please help me in devising or buying a
system for displaying changes in resistance caused by stretching a
conductive material. I have got the material and able to measure the
changes in resistance using an ohm meter. I am a computer programmer but
know nothing about electronics. Ideally I want to be able to read data
via USB port and then develop my own program to display the changes. Any
help on this will be appreciated.

The simplest way to start would be to use a USB data logger. Connect the
conductive material and one other resistor in a "voltage divider"
configuration, and measure the voltage from the junction between the
two, referenced to ground. Then do the math to work backwards to the
resistance.

http://www.mccdaq.com/usb-data-acquisition/USB-1208-Series.aspx> is one
option. It includes a basic data logging application as well as the
necessary DLLs for you to write a more sophisticated app, if desired.
The presence of (controllable) analog outs as well as a 5V output would
make your project pretty easy, requiring just this pod plus a resistor
and a little software.

http://www.dataq.com/usb-data-acquisition/usb-data-acquisition.html is
another popular source. I don't think they're as flexible as the MCC
pods but they are an option.

Gilak, how much sensitivity do you need? Is this a hobby or school
project? A production device? What sort of production volumes are you
dealing with? Who's going to be building it? Do you have a target price
for the end system?

Rich's idea is a good one, but you'll have a little bit of signal buried
in a whole lot of noise.

Assuming that it's precise enough, the very easiest way to do this would
be to get a digital multimeter with USB output and read the resistance of
your wire directly. I'd be kind of surprised if you couldn't buy a
suitable (again, assuming sufficient accuracy) from Radio Shack for less
than $30. If you need this for a product, then go looking for USB DAQ
modules that'll measure resistance accurately.

If a cost-effective DMM isn't going to be precise enough, then your best
bet is probably to use a bridge and amplifier, although running a known
current through the wire and measuring its voltage drop with a really
accurate ADC has its merits (and complications). Let us know the details
of what sort of project this is, and we can help you better.

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com

 

[gilak]

On Apr 5, 5:58 pm, Tim Wescott <t...@seemywebsite.com> wrote:

On Thu, 05 Apr 2012 11:33:37 -0400, Rich Webb wrote:
On Thu, 5 Apr 2012 08:12:03 -0700 (PDT), gilak <bkas...@gmail.com
wrote:

I wonder whether someone could please help me in devising or buying a
system for displaying changes in resistance caused by stretching a
conductive material. I have got the material and able to measure the
changes in resistance using an ohm meter. I am a computer programmer but
know nothing about electronics. Ideally I want to be able to read data
via USB port and then develop my own program to display the changes. Any
help on this will be appreciated.

The simplest way to start would be to use a USB data logger. Connect the
conductive material and one other resistor in a "voltage divider"
configuration, and measure the voltage from the junction between the
two, referenced to ground. Then do the math to work backwards to the
resistance.

http://www.mccdaq.com/usb-data-acquisition/USB-1208-Series.aspx> is one
option. It includes a basic data logging application as well as the
necessary DLLs for you to write a more sophisticated app, if desired.
The presence of (controllable) analog outs as well as a 5V output would
make your project pretty easy, requiring just this pod plus a resistor
and a little software.

http://www.dataq.com/usb-data-acquisition/usb-data-acquisition.htmlis
another popular source. I don't think they're as flexible as the MCC
pods but they are an option.

Gilak, how much sensitivity do you need?  Is this a hobby or school
project?  A production device?  What sort of production volumes are you
dealing with?  Who's going to be building it?  Do you have a target price
for the end system?

Rich's idea is a good one, but you'll have a little bit of signal buried
in a whole lot of noise.

Assuming that it's precise enough, the very easiest way to do this would
be to get a digital multimeter with USB output and read the resistance of
your wire directly.  I'd be kind of surprised if you couldn't buy a
suitable (again, assuming sufficient accuracy) from Radio Shack for less
than $30.  If you need this for a product, then go looking for USB DAQ
modules that'll measure resistance accurately.

If a cost-effective DMM isn't going to be precise enough, then your best
bet is probably to use a bridge and amplifier, although running a known
current through the wire and measuring its voltage drop with a really
accurate ADC has its merits (and complications).  Let us know the details
of what sort of project this is, and we can help you better.

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Softwarehttp://www.wescottdesign.com

A big thank you to Rand, Rich and Tim for their prompt replies.

Randy: I would like to start with a pre-built test instrument and then
progress to devising a bespoke system. The system will eventually be
used in a patient monitoring environment and needs to be packaged in
a form that is easy to operate and maintain. I think I could probably
afford a hand-held oscilloscope with DVM functions and USB
connectivity.

Rich: Excellent advise. I had a look at USB-1208 Series data loggers
specification. I am hoping it will give me the flexibility in design
and user presentation that I need..

Tim: It will be a one-of-prototype for use in a health care
environment. This is a proof of concept research project and if
successful we will approach a manufacturer for a production model. I
didn’t know you could buy digital multimeter with USB connectivity.
If I could read the output direct from a multimeter then it would be a
good start in demonstrating the concept behind the project.

 

[Jamie]

gilak wrote:

On Apr 5, 5:58 pm, Tim Wescott <t...@seemywebsite.com> wrote:

On Thu, 05 Apr 2012 11:33:37 -0400, Rich Webb wrote:

On Thu, 5 Apr 2012 08:12:03 -0700 (PDT), gilak <bkas...@gmail.com
wrote:

I wonder whether someone could please help me in devising or buying a
system for displaying changes in resistance caused by stretching a
conductive material. I have got the material and able to measure the
changes in resistance using an ohm meter. I am a computer programmer but
know nothing about electronics. Ideally I want to be able to read data
via USB port and then develop my own program to display the changes. Any
help on this will be appreciated.

The simplest way to start would be to use a USB data logger. Connect the
conductive material and one other resistor in a "voltage divider"
configuration, and measure the voltage from the junction between the
two, referenced to ground. Then do the math to work backwards to the
resistance.

http://www.mccdaq.com/usb-data-acquisition/USB-1208-Series.aspx> is one
option. It includes a basic data logging application as well as the
necessary DLLs for you to write a more sophisticated app, if desired.
The presence of (controllable) analog outs as well as a 5V output would
make your project pretty easy, requiring just this pod plus a resistor
and a little software.

http://www.dataq.com/usb-data-acquisition/usb-data-acquisition.htmlis
another popular source. I don't think they're as flexible as the MCC
pods but they are an option.

Gilak, how much sensitivity do you need? Is this a hobby or school
project? A production device? What sort of production volumes are you
dealing with? Who's going to be building it? Do you have a target price
for the end system?

Rich's idea is a good one, but you'll have a little bit of signal buried
in a whole lot of noise.

Assuming that it's precise enough, the very easiest way to do this would
be to get a digital multimeter with USB output and read the resistance of
your wire directly. I'd be kind of surprised if you couldn't buy a
suitable (again, assuming sufficient accuracy) from Radio Shack for less
than $30. If you need this for a product, then go looking for USB DAQ
modules that'll measure resistance accurately.

If a cost-effective DMM isn't going to be precise enough, then your best
bet is probably to use a bridge and amplifier, although running a known
current through the wire and measuring its voltage drop with a really
accurate ADC has its merits (and complications). Let us know the details
of what sort of project this is, and we can help you better.

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Softwarehttp://www.wescottdesign.com


A big thank you to Rand, Rich and Tim for their prompt replies.

Randy: I would like to start with a pre-built test instrument and then
progress to devising a bespoke system. The system will eventually be
used in a patient monitoring environment and needs to be packaged in
a form that is easy to operate and maintain. I think I could probably
afford a hand-held oscilloscope with DVM functions and USB
connectivity.

Rich: Excellent advise. I had a look at USB-1208 Series data loggers
specification. I am hoping it will give me the flexibility in design
and user presentation that I need..

Tim: It will be a one-of-prototype for use in a health care
environment. This is a proof of concept research project and if
successful we will approach a manufacturer for a production model. I
didn’t know you could buy digital multimeter with USB connectivity.
If I could read the output direct from a multimeter then it would be a
good start in demonstrating the concept behind the project.

Look on line for FLuke DMM's, Most of the upper models have a serial
connection option. This will allow you to monitor exactly what the DMM
is monitoring..

A 189/289 is good for this.

P.S.

You didn't specify as to how low of R you are measuring? That is
important.

Jamie

 

[Jasen Betts]

On 2012-04-05, gilak <bkasmai@gmail.com> wrote:

I wonder whether someone could please help me in devising or buying a
system for displaying changes in resistance caused by stretching a
conductive material. I have got the material and able to measure the
changes in resistance using an ohm meter. I am a computer programmer
but know nothing about electronics. Ideally I want to be able to read
data via USB port and then develop my own program to display the
changes. Any help on this will be appreciated.

what range of resistance are you seeing.
is using the joystick port a viable option, or do you need more than 4
axes?

--
⚂⚃ 100% natural

--- Posted via news://freenews.netfront.net/ - Complaints to news@netfront.net ---

 

[Bob Masta]

On Thu, 5 Apr 2012 08:12:03 -0700 (PDT), gilak
<bkasmai@gmail.com> wrote:

I wonder whether someone could please help me in devising or buying a
system for displaying changes in resistance caused by stretching a
conductive material. I have got the material and able to measure the
changes in resistance using an ohm meter. I am a computer programmer
but know nothing about electronics. Ideally I want to be able to read
data via USB port and then develop my own program to display the
changes. Any help on this will be appreciated.

If you have a Windows computer with a sound card, you
already have all the hardware you need. My Daqarta software
(shameless plug) can generate a driving signal from the
sound card output that you would apply to the material
through a resistor. Then connect the sound card input
across the material and observe the change in amplitude of
the waveform as you stretch the material.

The basic circuit is a simple voltage divider:
(View with monospaced font.)

Output >---R----.-----> Input
|
X
|
Ground>---------.------> Ground

For decent resistance measurments, make R ten to 100 times
that of stretch material X. (So it approximates a constant
current source, like you'd have in an ohmmeter.) The sound
card has a big dynamic range, so you can boost the input
gain and display magnification to make up for the loss in
the voltage divider and still get a nice display from
Daqarta.

Sound cards are not intrinsically calibrated, but you can do
that easily for this simple setup. The max output from the
card is typically +/-2.5V p-p or less, which is also about
the max input voltage range.

You'll need to rig up a cable to connect your material and
resistor to the sound card. I suggest buying a cheap cable
with male stereo connectors on both ends, and cutting it in
half. That way you have a cable for the sound card output,
and one for the input. Carefully strip the cut ends and
expose the white (left) conductors on each. Use clip leads
(or solder a more permanent arrangement) to connect to the
voltage divider. The braided or twisted shield is the
common ground.

Click the Input button on the Daqarta toolbar to view the
input signal. You will also need to click the thin unmarked
button directly beneath that to open the Input control
dialog, to select Line In and adjust the range.

The Daqarta Generator defaults to a 440 Hz sine on the Left
Out line, which should be fine for this. Just click the
Generator button on the toolbar. A volume control dialog
will open the first time you do that, or use F9 at any other
time. Make sure that the Mute button is off and raise the
volume (and / or input range) until you see a nice sine wave
on the trace. Hitting the PgUp key increases the screen
magnification.

One you get this working, so you can see the waveform
amplitude change when you stretch the material, you can
activate the Voltmeter (ALT+V or use the Options menu). To
calibrate, the simplest approach is probably to replace the
material with a known resistance.

To get a strip-chart type plot, click the thin buttun under
X-Axis and activate Decimate, as well as the Demod buttun
below that. That plots the peak amplitude versus time,
instead of the raw waveform. (You'll probably need to
toggle Trigger off in the toolbar as well.) The Decimate
factor controls the speed.

You can save it to a file with the DDisk button.
Alternatively, you can use Daqarta's macro system to save a
data log text file.

Right-click any button or menu line to get Help on any
control.

Daqarta has a 30-session/30-day free trial, which is
probably more than you need to do this project.

I'd be glad to answer any further questions, here or via the
Contact page on the Daqarta website.

Best regards,


Bob Masta

DAQARTA v6.02
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, FREE Signal Generator
Pitch Track, Pitch-to-MIDI
Science with your sound card!

 

[Tim Wescott]

On Thu, 05 Apr 2012 17:44:21 -0400, Jamie wrote:

gilak wrote:

On Apr 5, 5:58 pm, Tim Wescott <t...@seemywebsite.com> wrote:

On Thu, 05 Apr 2012 11:33:37 -0400, Rich Webb wrote:

On Thu, 5 Apr 2012 08:12:03 -0700 (PDT), gilak <bkas...@gmail.com
wrote:

I wonder whether someone could please help me in devising or buying a
system for displaying changes in resistance caused by stretching a
conductive material. I have got the material and able to measure the
changes in resistance using an ohm meter. I am a computer programmer
but know nothing about electronics. Ideally I want to be able to read
data via USB port and then develop my own program to display the
changes. Any help on this will be appreciated.

The simplest way to start would be to use a USB data logger. Connect
the conductive material and one other resistor in a "voltage divider"
configuration, and measure the voltage from the junction between the
two, referenced to ground. Then do the math to work backwards to the
resistance.

http://www.mccdaq.com/usb-data-acquisition/USB-1208-Series.aspx> is
one option. It includes a basic data logging application as well as
the necessary DLLs for you to write a more sophisticated app, if
desired. The presence of (controllable) analog outs as well as a 5V
output would make your project pretty easy, requiring just this pod
plus a resistor and a little software.

http://www.dataq.com/usb-data-acquisition/usb-data-acquisition.htmlis
another popular source. I don't think they're as flexible as the MCC
pods but they are an option.

Gilak, how much sensitivity do you need? Is this a hobby or school
project? A production device? What sort of production volumes are you
dealing with? Who's going to be building it? Do you have a target
price for the end system?

Rich's idea is a good one, but you'll have a little bit of signal
buried in a whole lot of noise.

Assuming that it's precise enough, the very easiest way to do this
would be to get a digital multimeter with USB output and read the
resistance of your wire directly. I'd be kind of surprised if you
couldn't buy a suitable (again, assuming sufficient accuracy) from
Radio Shack for less than $30. If you need this for a product, then go
looking for USB DAQ modules that'll measure resistance accurately.

If a cost-effective DMM isn't going to be precise enough, then your
best bet is probably to use a bridge and amplifier, although running a
known current through the wire and measuring its voltage drop with a
really accurate ADC has its merits (and complications). Let us know
the details of what sort of project this is, and we can help you
better.

--
My liberal friends think I'm a conservative kook. My conservative
friends think I'm a liberal kook. Why am I not happy that they have
found common ground?

Tim Wescott, Communications, Control, Circuits &
Softwarehttp://www.wescottdesign.com


A big thank you to Rand, Rich and Tim for their prompt replies.

Randy: I would like to start with a pre-built test instrument and then
progress to devising a bespoke system. The system will eventually be
used in a patient monitoring environment and needs to be packaged in a
form that is easy to operate and maintain. I think I could probably
afford a hand-held oscilloscope with DVM functions and USB
connectivity.

Rich: Excellent advise. I had a look at USB-1208 Series data loggers
specification. I am hoping it will give me the flexibility in design
and user presentation that I need..

Tim: It will be a one-of-prototype for use in a health care
environment. This is a proof of concept research project and if
successful we will approach a manufacturer for a production model. I
didn’t know you could buy digital multimeter with USB connectivity. If
I could read the output direct from a multimeter then it would be a
good start in demonstrating the concept behind the project.

Look on line for FLuke DMM's, Most of the upper models have a serial
connection option. This will allow you to monitor exactly what the DMM
is monitoring..

A 189/289 is good for this.

P.S.

You didn't specify as to how low of R you are measuring? That is
important.

Oh my, it is - I missed that detail. Bad Dobby. Bad Dobby.

Constant current sources are pretty easy to cook up (or just buy), that
plus a Kelvin connection to a sensitive-enough DMM might work nicely.
Even a constant-current source on a board next to a decent low-offset op-
amp, thence to a cheap DMM, would still be fairly low-effort.

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com