Electronics > Metrology

Precision Resistors - General Thread

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sahko123:
Is there any particular reason certain oils are used? Is because of corrosion issues? Or even humidity issues?

leighcorrigall:

--- Quote from: sahko123 on May 20, 2022, 09:38:54 pm ---Is there any particular reason certain oils are used? Is because of corrosion issues? Or even humidity issues?

--- End quote ---

Some oils spoil or are corrosive because of contamination. Other factors are heat transfer and high-resistance insulation.

bsw_m:
I has measure diameter of glass insulated cast microwire from 100 MegaOhm resistor.
Wire without insulation: 2um  :o
Wire with glass insulation: 14um
Sorry now I cannot take the microwire photo from my microscope when I don't have the photoattachment for my microscope.

P.S.
I try take photo from eyepiece with phone camera. Quality not good, but..
625x magnification.

TimFox:

--- Quote from: leighcorrigall on May 20, 2022, 10:03:13 pm ---
--- Quote from: sahko123 on May 20, 2022, 09:38:54 pm ---Is there any particular reason certain oils are used? Is because of corrosion issues? Or even humidity issues?

--- End quote ---

Some oils spoil or are corrosive because of contamination. Other factors are heat transfer and high-resistance insulation.

--- End quote ---

Before I retired, we used Shell DialaTM transformer oil for insulating high-voltage supplies.
So far as I could tell, it was basically pure motor oil, with BHT (or similar) added to retard oxidation.
Butylated hydroxytoluene is an anti-oxidant, whose use in food is controversial.
(For high-voltage purposes, it was necessary to pump a vacuum on top of it to remove bubbles.)

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