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scanner80
 
Posts: n/a
Default Viewing an ohms change on an oscope???

Hello,
I'm looking for a circuit I can build or equipment I can buy
so I can time how long an ohms change is. I would like to build it if
possible . I would like to view it on a scope.
One example would be a starting ohms reading from a device of 1355 ohms. It
will increase by approx. 20 ohms
and then return to 1355 ohms. The time it will take is approx. 19 seconds. I
will need to be able to see a change as small as 1 ohm if possible , but the
most important thing is to see the reading change from 1355 and return to
1355 ohms. I need to then measure the time with cursers on a scope.
I know a respiration monitor can see and display an ohms change , but I need
a way to exactly measure the change.
I will be greatful for any help.
Thank you,
Jeff


  #2   Report Post  
DBLEXPOSURE
 
Posts: n/a
Default


"scanner80" wrote in message
...
Hello,
I'm looking for a circuit I can build or equipment I can buy
so I can time how long an ohms change is. I would like to build it if
possible . I would like to view it on a scope.
One example would be a starting ohms reading from a device of 1355 ohms.
It
will increase by approx. 20 ohms
and then return to 1355 ohms. The time it will take is approx. 19 seconds.
I
will need to be able to see a change as small as 1 ohm if possible , but
the
most important thing is to see the reading change from 1355 and return to
1355 ohms. I need to then measure the time with cursers on a scope.
I know a respiration monitor can see and display an ohms change , but I
need
a way to exactly measure the change.
I will be greatful for any help.
Thank you,
Jeff



Jeff:



To measure resistance you need to apply a voltage and then
measure the current. Another way is to use a "voltage divider", put your
changing resistance in series with a known resistance, apply a voltage to
the circuit and monitor the voltage dropped across the known resistor. As
your changing resistance decreases current in the circuit will increase and
the voltage drop across your known resistor will increase. This will all be
linear so you will be able to make notations on your scope graticule so that
you can directly readout the display in ohms.



You will want to use a regulated voltage source. A look into Ohms law will
provide the math for you to make the calculations..


  #3   Report Post  
scanner80
 
Posts: n/a
Default

I just want to be able to measure the time it takes from when the resistance
leaves 1355 ohms and returns to 1355. I can do it with a meter and a
stopwatch, but I was looking for a more verifiable way to do it. I want to
remove human error. This is for calibration purposes.
Is there any type of simple timer or timer circuit that can will trigger as
the ohms changes and stop when it returns?
Jeff
"DBLEXPOSURE" wrote in message
...

"scanner80" wrote in message
...
Hello,
I'm looking for a circuit I can build or equipment I can buy
so I can time how long an ohms change is. I would like to build it if
possible . I would like to view it on a scope.
One example would be a starting ohms reading from a device of 1355 ohms.
It
will increase by approx. 20 ohms
and then return to 1355 ohms. The time it will take is approx. 19

seconds.
I
will need to be able to see a change as small as 1 ohm if possible , but
the
most important thing is to see the reading change from 1355 and return

to
1355 ohms. I need to then measure the time with cursers on a scope.
I know a respiration monitor can see and display an ohms change , but I
need
a way to exactly measure the change.
I will be greatful for any help.
Thank you,
Jeff



Jeff:



To measure resistance you need to apply a voltage and then
measure the current. Another way is to use a "voltage divider", put your
changing resistance in series with a known resistance, apply a voltage to
the circuit and monitor the voltage dropped across the known resistor. As
your changing resistance decreases current in the circuit will increase

and
the voltage drop across your known resistor will increase. This will all

be
linear so you will be able to make notations on your scope graticule so

that
you can directly readout the display in ohms.



You will want to use a regulated voltage source. A look into Ohms law

will
provide the math for you to make the calculations..




  #4   Report Post  
DBLEXPOSURE
 
Posts: n/a
Default


"scanner80" wrote in message
...
I just want to be able to measure the time it takes from when the
resistance
leaves 1355 ohms and returns to 1355. I can do it with a meter and a
stopwatch, but I was looking for a more verifiable way to do it. I want to
remove human error. This is for calibration purposes.
Is there any type of simple timer or timer circuit that can will trigger
as
the ohms changes and stop when it returns?
Jeff
"DBLEXPOSURE" wrote in message
...

"scanner80" wrote in message
...
Hello,
I'm looking for a circuit I can build or equipment I can buy
so I can time how long an ohms change is. I would like to build it if
possible . I would like to view it on a scope.
One example would be a starting ohms reading from a device of 1355
ohms.
It
will increase by approx. 20 ohms
and then return to 1355 ohms. The time it will take is approx. 19

seconds.
I
will need to be able to see a change as small as 1 ohm if possible ,
but
the
most important thing is to see the reading change from 1355 and return

to
1355 ohms. I need to then measure the time with cursers on a scope.
I know a respiration monitor can see and display an ohms change , but I
need
a way to exactly measure the change.
I will be greatful for any help.
Thank you,
Jeff



Jeff:



To measure resistance you need to apply a voltage and then
measure the current. Another way is to use a "voltage divider", put your
changing resistance in series with a known resistance, apply a voltage to
the circuit and monitor the voltage dropped across the known resistor.
As
your changing resistance decreases current in the circuit will increase

and
the voltage drop across your known resistor will increase. This will all

be
linear so you will be able to make notations on your scope graticule so

that
you can directly readout the display in ohms.



You will want to use a regulated voltage source. A look into Ohms law

will
provide the math for you to make the calculations..





Typically they prefer that you bottom post in this group. Doesn't bother me
but, when in Rome..........


Well, I don't have time at the moment to work out all the details; maybe
someone else will chime in with more help. But I can at least get you
started.



First, use the voltage divider circuit I talked about in the previous post.
Instead of monitoring the voltage across the known resistance with your
scope, use that voltage to drive the Vin of a simple "Op Amp non inverting
comparator" circuit. Here is a link to get you started with the comparator.
http://home.maine.rr.com/randylinscott/learn.htm



The idea is when your voltage across the known resistance of the voltage
divider exceeds the Vref of the comparator the output of the comparator will
go high.



This output voltage can be used to drive a reed relay. You can find reed
relays that will energize with very little coil current. The relay will be
used instead of the transistor depicted in the schematic of the
non-inverting comparator shown on the link provided.



Now get yourself a cheap stopwatch that has one button that will both start
and stop. Wire the switch contacts of the relay across the start/stop
switch of the watch.



There are more eloquent ways to go about it but this will be a pretty easy
and cheap way to get the job done. I have left a lot of the design to you,
resistor sizes, voltages etc.. Newark Electronics might be a good place to
find the relay. The 741 op-amp crosses to a NTE941M, which can be found
here http://www.weisd.com/store2/ntesemi/NTE941M.html



Well, duty calls, gota run for now.........











  #5   Report Post  
John Fields
 
Posts: n/a
Default

On Fri, 5 Aug 2005 23:23:22 -0500, "scanner80"
wrote:

I just want to be able to measure the time it takes from when the resistance
leaves 1355 ohms and returns to 1355. I can do it with a meter and a
stopwatch, but I was looking for a more verifiable way to do it. I want to
remove human error. This is for calibration purposes.
Is there any type of simple timer or timer circuit that can will trigger as
the ohms changes and stop when it returns?


---
You could do it with something as simple as a voltage comparator
detecting the resistance change and using its (the voltage
comparator's) output to gate a counter, but you need to supply more
details about the resistance before we can help you much. For
example, what is the resistance, physically, and how is it being
used? Does it have a voltage across it?

--
John Fields
Professional Circuit Designer


  #6   Report Post  
John Fields
 
Posts: n/a
Default

On Sat, 06 Aug 2005 05:58:56 -0500, John Fields
wrote:

On Fri, 5 Aug 2005 23:23:22 -0500, "scanner80"
wrote:

I just want to be able to measure the time it takes from when the resistance
leaves 1355 ohms and returns to 1355. I can do it with a meter and a
stopwatch, but I was looking for a more verifiable way to do it. I want to
remove human error. This is for calibration purposes.
Is there any type of simple timer or timer circuit that can will trigger as
the ohms changes and stop when it returns?


---
You could do it with something as simple as a voltage comparator
detecting the resistance change and using its (the voltage
comparator's) output to gate a counter, but you need to supply more
details about the resistance before we can help you much. For
example, what is the resistance, physically, and how is it being
used? Does it have a voltage across it?


---
BTW, I just noticed that you also posted your query to seb
separately. A more convenient way to post, if you have the same
message which you'd like to post to multiple groups is to
'crosspost'. All you have to do is type the names of all the
newsgroups you want the post to go to into the "newsgroups" (or
whatever it's called in your reader) line and it'll go to all of
them. It's a good way to do it because then the entire thread is
available to whoever wants to read it without having to hop back and
forth between groups. This post will go to alt.electronics and
sci.electronics.basics and, if you care to reply to it, so will your
reply, and so on.

--
John Fields
Professional Circuit Designer
  #7   Report Post  
John Fields
 
Posts: n/a
Default

On Fri, 5 Aug 2005 21:12:21 -0500, "DBLEXPOSURE"
wrote:


"scanner80" wrote in message
...
Hello,
I'm looking for a circuit I can build or equipment I can buy
so I can time how long an ohms change is. I would like to build it if
possible . I would like to view it on a scope.
One example would be a starting ohms reading from a device of 1355 ohms.
It
will increase by approx. 20 ohms
and then return to 1355 ohms. The time it will take is approx. 19 seconds.
I
will need to be able to see a change as small as 1 ohm if possible , but
the
most important thing is to see the reading change from 1355 and return to
1355 ohms. I need to then measure the time with cursers on a scope.
I know a respiration monitor can see and display an ohms change , but I
need
a way to exactly measure the change.
I will be greatful for any help.
Thank you,
Jeff



Jeff:



To measure resistance you need to apply a voltage and then
measure the current. Another way is to use a "voltage divider", put your
changing resistance in series with a known resistance, apply a voltage to
the circuit and monitor the voltage dropped across the known resistor. As
your changing resistance decreases current in the circuit will increase and
the voltage drop across your known resistor will increase. This will all be
linear so you will be able to make notations on your scope graticule so that
you can directly readout the display in ohms.


---
That won't work, for several reasons.

The first is that the resistance change is too small to give a
detectable deflection of the scope trace with the scope vertical
input voltage range being whatever it needs to be to keep the trace
on the screen. For example:




E1
|
[R1]
|
+---E2
|
[R2]
|
0V

If we let E1 equal 1 volt and R1 and R2 equal 1000 ohms and 1355
ohms, respectively, then with R2 at 1355 ohms we'll have:


E1R2 1V * 1355R
E2 = --------- = --------------- = 0.575 volts
R1 + R2 1100R + 1355R


and with R2 at the high end, (1375 ohms) W2 will be equal to 0.579V.

That's a change of only four millivolts, which would give you a
deflection of two boxes with an input sensitivity of 2mV per box.
That might be OK, but look at what that 4mV signal is riding on: a
voltage about 150 times higher, so no matter how you adjust the
vertical sensitivity and trace position controls, I don't believe
you're going to wind up with anything that works.


The second problem is going to be triggering the scope at the
instant the resistance starts to rise, unless an external trigger
can be rigged using a comparator, and the third problem is going to
be the accuracy of the timebase and marking the screen properly when
the trace crosses the reference. In other words, when was the last
time you had your scope calibrated and how good are you with that
grease pencil/sharpie?

BTW, that 4mV change _won't_ be linear, but it doesn't matter since
all he really wants to do is look for the crossing.
---

You will want to use a regulated voltage source. A look into Ohms law will
provide the math for you to make the calculations..


---
Woudn't have hurt for you to run the numbers, and it would have
saved me a post.


Just as an aside, there _is_ a way to do it using a couple of
voltage dividers to make a bridge, like this:


E1--------+----------------+
| |
[R1] [R3]
| |
+---E2 E3---+
| |
[R2] [R4]
| |
0V--------+----------------+


What happens here is that when the ratio of R1 to R2 equals the
ratio of R3 to R4, then E2 will equal E3 and you can connect a scope
between E2 and E3 and measure the voltage between them without
having to worry about the offset you get with a half-bridge.

For ease of use, R3R4 could be a pot which could be adjusted for
precisely zero volts across E2 and E3 when R2 was at 1355 ohms, or
for greater resolution,


E1--------+------------------+
| |
[R1] [R3]
| |
+---E2 E3---[POT]
| |
[R2] [R4]
| |
0V--------+------------------+

One caveat, the supply should be floating or, if the scope can do
it, it should be set to display E2 minus E3













--
John Fields
Professional Circuit Designer
  #8   Report Post  
DBLEXPOSURE
 
Posts: n/a
Default


"John Fields" wrote in message
news
On Fri, 5 Aug 2005 21:12:21 -0500, "DBLEXPOSURE"
wrote:


"scanner80" wrote in message
...
Hello,
I'm looking for a circuit I can build or equipment I can buy
so I can time how long an ohms change is. I would like to build it if
possible . I would like to view it on a scope.
One example would be a starting ohms reading from a device of 1355 ohms.
It
will increase by approx. 20 ohms
and then return to 1355 ohms. The time it will take is approx. 19
seconds.
I
will need to be able to see a change as small as 1 ohm if possible , but
the
most important thing is to see the reading change from 1355 and return
to
1355 ohms. I need to then measure the time with cursers on a scope.
I know a respiration monitor can see and display an ohms change , but I
need
a way to exactly measure the change.
I will be greatful for any help.
Thank you,
Jeff



Jeff:



To measure resistance you need to apply a voltage and then
measure the current. Another way is to use a "voltage divider", put your
changing resistance in series with a known resistance, apply a voltage to
the circuit and monitor the voltage dropped across the known resistor. As
your changing resistance decreases current in the circuit will increase
and
the voltage drop across your known resistor will increase. This will all
be
linear so you will be able to make notations on your scope graticule so
that
you can directly readout the display in ohms.


---
That won't work, for several reasons.

The first is that the resistance change is too small to give a
detectable deflection of the scope trace with the scope vertical
input voltage range being whatever it needs to be to keep the trace
on the screen. For example:




E1
|
[R1]
|
+---E2
|
[R2]
|
0V

If we let E1 equal 1 volt and R1 and R2 equal 1000 ohms and 1355
ohms, respectively, then with R2 at 1355 ohms we'll have:


E1R2 1V * 1355R
E2 = --------- = --------------- = 0.575 volts
R1 + R2 1100R + 1355R


and with R2 at the high end, (1375 ohms) W2 will be equal to 0.579V.

That's a change of only four millivolts, which would give you a
deflection of two boxes with an input sensitivity of 2mV per box.
That might be OK, but look at what that 4mV signal is riding on: a
voltage about 150 times higher, so no matter how you adjust the
vertical sensitivity and trace position controls, I don't believe
you're going to wind up with anything that works.


The second problem is going to be triggering the scope at the
instant the resistance starts to rise, unless an external trigger
can be rigged using a comparator, and the third problem is going to
be the accuracy of the timebase and marking the screen properly when
the trace crosses the reference. In other words, when was the last
time you had your scope calibrated and how good are you with that
grease pencil/sharpie?

BTW, that 4mV change _won't_ be linear, but it doesn't matter since
all he really wants to do is look for the crossing.
---

You will want to use a regulated voltage source. A look into Ohms law
will
provide the math for you to make the calculations..


---
Woudn't have hurt for you to run the numbers, and it would have
saved me a post.


Just as an aside, there _is_ a way to do it using a couple of
voltage dividers to make a bridge, like this:


E1--------+----------------+
| |
[R1] [R3]
| |
+---E2 E3---+
| |
[R2] [R4]
| |
0V--------+----------------+


What happens here is that when the ratio of R1 to R2 equals the
ratio of R3 to R4, then E2 will equal E3 and you can connect a scope
between E2 and E3 and measure the voltage between them without
having to worry about the offset you get with a half-bridge.

For ease of use, R3R4 could be a pot which could be adjusted for
precisely zero volts across E2 and E3 when R2 was at 1355 ohms, or
for greater resolution,


E1--------+------------------+
| |
[R1] [R3]
| |
+---E2 E3---[POT]
| |
[R2] [R4]
| |
0V--------+------------------+

One caveat, the supply should be floating or, if the scope can do
it, it should be set to display E2 minus E3













--
John Fields
Professional Circuit Designer






The first is that the resistance change is too small to give a
detectable deflection of the scope trace with the scope vertical
input voltage range being whatever it needs to be to keep the trace
on the screen.




If a 30V source is used (My bench supply is 0-60Vdc regulated, BK 1623A) and
1K for the known resistance a difference in 20 Ohms of the resistor under
test will result in a rise of 100mV across the known resistance



30Vdc

|

|

R1 (1355-1375 Ohms)

|

|

R2 1K Ohm -

|

|

Gnd------------





1355+1000=2355 Ohms



30/2355=12.7mA



12.7mA X 1000 Ohms = 12.7V



And the high end



1375+1000=2375 Ohms



30/2375=12.6mA



12.6mA X 1000 Ohms = 12.6V



A difference of



12.7-12.6 = 100mV








The second problem is going to be triggering the scope at the
instant the resistance starts to rise, unless an external trigger
can be rigged using a comparator, and the third problem is going to
be the accuracy of the timebase and marking the screen properly when
the trace crosses the reference. In other words, when was the last
time you had your scope calibrated and how good are you with that
grease pencil/sharpie




will increase by approx. 20 ohms
and then return to 1355 ohms. The time it will take is approx. 19

seconds.



If this whole process takes 19 seconds, triggering shouldn't be an issue.
Remember, he was using a stopwatch to measure the time, so, just use a quick
time base and watch the green line rise and fall.



10mV/cm gives me full deflection and I have plenty of range on the Vert.
position to bring the trace to the bottom of the screen. My scope is now
measuring 2 ohms/cm. I don't know why this would not be linear. Scope is
calibrated annually.



As for not running the number last night, I was doing other things and
fiddled with this while on break. And, I didn't want to steal your thunder.
I knew you would come up with a more elegant way of doing this. I'm just a
hack anyway..



I do like your bridge idea...






  #9   Report Post  
John Fields
 
Posts: n/a
Default

On Sat, 6 Aug 2005 11:09:05 -0500, "DBLEXPOSURE"
wrote:



If a 30V source is used (My bench supply is 0-60Vdc regulated, BK 1623A) and
1K for the known resistance a difference in 20 Ohms of the resistor under
test will result in a rise of 100mV across the known resistance


snip

12.7-12.6 = 100mV



If this whole process takes 19 seconds, triggering shouldn't be an issue.
Remember, he was using a stopwatch to measure the time, so, just use a quick
time base and watch the green line rise and fall.


---
But, remember, he said he didn't want to do it that way any more.
---

10mV/cm gives me full deflection and I have plenty of range on the Vert.
position to bring the trace to the bottom of the screen. My scope is now
measuring 2 ohms/cm. I don't know why this would not be linear. Scope is
calibrated annually.


---
Did you actually try it?

I've got a Tektronix 2215, and with a 15V input, the best I can do
is 1V/box and still keep the trace on the scope with the position
control.

I didn't say the scope's response wasn't linear, I was talking about
the change in the output voltage from the divider as a function of
the change in resistance of the DUT.
---


I do like your bridge idea...



---
Thanks, but the credit should go to Samuel Hunter Christie and Sir
Charles Wheatstone.


--
John Fields
Professional Circuit Designer
  #10   Report Post  
JeffM
 
Posts: n/a
Default

...reading from a device of 1355 ohms...
Jeff (scanner80)


Posting the same question individually to multiple groups
is not only foolish (worse than linked cross-posting), it is selfish.

Those people who do not visit each of the groups
will not benefit by the intelligence of the responses at those other
groups.

Despite those folks who warn about EXCESSIVE cross-posting,
posting the same question individually to 4 groups
is a really bad approach.
http://groups-beta.google.com/groups...Fzc364xXu3mYhA

This practice robs those people
who do not habitually visit all the groups
of the wisdom of others on the topic.
It also doesn't let everyone know
when the question has been answered sufficiently.

Most importantly, it does not allow those in 1 group
to gain from further details revealed in another group.
http://groups-beta.google.com/group/...he-resistances

If the query is relevant to multiple groups,
put the names of ALL the groups in which you would like it to appear
on the Groups line (the To line) THE FIRST TIME you post it.

Proper use of the Followup-To line is also useful.



  #11   Report Post  
DBLEXPOSURE
 
Posts: n/a
Default


"John Fields" wrote in message
...
On Sat, 6 Aug 2005 11:09:05 -0500, "DBLEXPOSURE"
wrote:



If a 30V source is used (My bench supply is 0-60Vdc regulated, BK 1623A)
and
1K for the known resistance a difference in 20 Ohms of the resistor under
test will result in a rise of 100mV across the known resistance


snip

12.7-12.6 = 100mV



If this whole process takes 19 seconds, triggering shouldn't be an issue.
Remember, he was using a stopwatch to measure the time, so, just use a
quick
time base and watch the green line rise and fall.


---
But, remember, he said he didn't want to do it that way any more.
---

10mV/cm gives me full deflection and I have plenty of range on the Vert.
position to bring the trace to the bottom of the screen. My scope is now
measuring 2 ohms/cm. I don't know why this would not be linear. Scope is
calibrated annually.


---
Did you actually try it?

I've got a Tektronix 2215, and with a 15V input, the best I can do
is 1V/box and still keep the trace on the scope with the position
control.

I didn't say the scope's response wasn't linear, I was talking about
the change in the output voltage from the divider as a function of
the change in resistance of the DUT.
---


I do like your bridge idea...



---
Thanks, but the credit should go to Samuel Hunter Christie and Sir
Charles Wheatstone.


--
John Fields
Professional Circuit Designer




Did you actually try it?




Yes, just now, and your correct, (as usual), I had to add another divider to
give me 12V to run into the B chnl. Then display (A-B).


I didn't say the scope's response wasn't linear, I was talking about
the change in the output voltage from the divider as a function of
the change in resistance of the DUT.


Wouldn't you consider an output change of 5mV for every 1 ohm change in the
DUT to be linear? To me, a nonlinear response would be something like, 5mV
for the first ohm of change, 7mV for the next ohm, 10 for the third, etc,
etc...











  #12   Report Post  
John Fields
 
Posts: n/a
Default

On Sat, 6 Aug 2005 13:00:57 -0500, "DBLEXPOSURE"
wrote:


"John Fields" wrote in message
.. .


Did you actually try it?




Yes, just now, and your correct, (as usual), I had to add another divider to
give me 12V to run into the B chnl. Then display (A-B).


I didn't say the scope's response wasn't linear, I was talking about
the change in the output voltage from the divider as a function of
the change in resistance of the DUT.


Wouldn't you consider an output change of 5mV for every 1 ohm change in the
DUT to be linear?


---
Yes, but that's not what's happening.


For your 30 volt circuit:


30V
|
[1000R]
|
+-----E
|
[R]
|
0V


This is what is:


R E DELTA E
------+----------+--------
1355 17.26115 -------
1356 17.26655 0.00540
1357 17.27196 0.00541
1358 17.27735 0.00539
1359 17.28275 0.00540
1360 17.28814 0.00539
1361 17.29352 0.00538
1362 17.29890 0.00538
1363 17.30427 0.00537
1364 17.30964 0.00537
1365 17.31501 0.00537
1366 17.32037 0.00536
1367 17.32573 0.00536
1368 17.33108 0.00535
1369 17.33643 0.00535
1370 17.34177 0.00534
1371 17.34711 0.00534
1372 17.35245 0.00534
1373 17.35777 0.00532
1374 17.36310 0.00533
1375 17.36842 0.00532


So, we see that for equal increments of resistance we _don't_ get
equal increments of voltage, therefore the relationship between
resistance and voltage isn't linear


To me, a nonlinear response would be something like, 5mV
for the first ohm of change, 7mV for the next ohm, 10 for the third, etc,
etc...


Yup!

--
John Fields
Professional Circuit Designer
  #13   Report Post  
Jasen Betts
 
Posts: n/a
Default

In article , scanner80 wrote:
Hello,


I'm looking for a circuit I can build or equipment I can buy
so I can time how long an ohms change is. I would like to build it if
possible . I would like to view it on a scope.
One example would be a starting ohms reading from a device of 1355 ohms. It
will increase by approx. 20 ohms
and then return to 1355 ohms. The time it will take is approx. 19 seconds. I
will need to be able to see a change as small as 1 ohm if possible , but the
most important thing is to see the reading change from 1355 and return to
1355 ohms. I need to then measure the time with cursers on a scope.
I know a respiration monitor can see and display an ohms change , but I need


a computer with apropriate software could do that using the 16-bit ADC in the
soundcard for input, or you can buy specialised devices that come with
software too...

or a microcontroller could be combineed with a current source and sensitive
DAC to output resistance readings 100 or so times a second...

Bye.
Jasen
  #14   Report Post  
Day Brown
 
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Jasen Betts wrote:
a computer with apropriate software could do that using the 16-bit ADC in the
soundcard for input, or you can buy specialised devices that come with
software too...

or a microcontroller could be combineed with a current source and sensitive
DAC to output resistance readings 100 or so times a second...

Waitaminit. I've long wondered if the soundcard could not take input
as data. Rather like the com port? where's this software? Linux?

  #15   Report Post  
Chris Head
 
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Hash: SHA1

Day Brown wrote:
Waitaminit. I've long wondered if the soundcard could not take input
as data. Rather like the com port? where's this software? Linux?


Sure thing. See:

http://polly.phys.msu.su/~zeld/oscill.html

for details. Try not to blow anything up.

Chris
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  #16   Report Post  
Jasen Betts
 
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In article , Day Brown wrote:
Jasen Betts wrote:
a computer with apropriate software could do that using the 16-bit ADC in the
soundcard for input, or you can buy specialised devices that come with
software too...

or a microcontroller could be combineed with a current source and sensitive
DAC to output resistance readings 100 or so times a second...

Waitaminit. I've long wondered if the soundcard could not take input
as data. Rather like the com port? where's this software? Linux?


in linux you can do

od -tx1 /dev/audio

and get a crude hexadecimal dump of the soundcards input mixer
(so to read line-in or mic you need to turn them on using aumix etc)

if you want something better google for this:

soundcard software oscilloscope linux


Bye.
Jasen
  #17   Report Post  
Day Brown
 
Posts: n/a
Default

Jasen Betts wrote:
Waitaminit. I've long wondered if the soundcard could not take input
as data. Rather like the com port? where's this software? Linux?

in linux you can do

od -tx1 /dev/audio

and get a crude hexadecimal dump of the soundcards input mixer
(so to read line-in or mic you need to turn them on using aumix etc)

if you want something better google for this:

soundcard software oscilloscope linux

Way kewl. thanx. got http://radio.linux.org.au/?sectpat=All&ordpat=title
which seems to have what I'm looking for.

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