[volt-nuts] Semi-precision high resistance measurement

[Steve Byan]

Hi Tom,

On Jun 17, 2013, at 2:48 PM, "Tom Miller" <tmiller11147 at verizon.net> wrote:

> 
> ----- Original Message ----- From: "Steve Byan" <stevebyan at verizon.net>
> Subject: [volt-nuts] Semi-precision high resistance measurement
> 
>> Any ideas as to what's going on? How can I improve my measurement procedure to get repeatable results? Do I really need better climate control even at the 3 1/2 or 4 1/2 digit level of precision? What's with the polarity sensitivity of the 8050A resistance measurements? Suggestions and advice would be gratefully accepted.
> 
> On the high value resistors, did you clean them well with 99% dry isopropyl alcohol (or maybe acetone) after you handled them? The oils on your skin are very conductive when measuring in the high megohm region.

They are still installed on the range switch. I did think about surface contamination and did clean them with anhydrous isopropyl, but I can't clean them that well without removing them from the range switch. I probably did clean most of the surface that's been handled during my disassembly of the instrument. 

Would the resistance of those oils be polarity sensitive?

I should check other high-value resistors, but I don't have much if anything handy that's over 1 megohm. I'll have to hunt around the shop and see what I can turn up.

Best regards,
-Steve

-- 
Steve Byan <stevebyan at me.com>
Littleton, MA 01460