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