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