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.

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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.

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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.
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I do like your bridge idea...


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


--
John Fields
Professional Circuit Designer