[volt-nuts] Wanted wirewound precision resistors and ESI DB877

Fabio Eboli FabioEb at quipo.it
Tue Jun 19 18:04:40 UTC 2012


Here I put some photos of the decade:
http://www.eevblog.com/forum/product-reviews-photos-and-discussion/db877-teardown/

Frank Stellmach <frank.stellmach at freenet.de> ha scritto:
> I think, you should better measure the resistance by a high  
> resolution DMM, on its normal OHM range.
> Thats much more stable and less power is dissipated. A comparison  
> between two of them is also much easier.

Yes I'm using a pair of multimeters: the keithley 2015 and
a solartron 7061, the keithley should be not far from real
values, but has a maximum count of 1200000, the
solartron is "zeroed" against the keithley,
has a maximum count of 21000000, permitting to compare
the 1M and 2M resistors without changing range and resolution.

I used the fluke to try to test for leackage, I
tought that if there was some leackage, the current
would have been higher than V/R ratio and not
proportional to the voltage.

> ingresses between the windings. I assume, your resistors are tubular  
> ones, with plastiv caps around, and they are not hermetically tight,  
> therefore they cant be filled completely for corrosion protection  
> and thermal  conductivity, like in the Vishay metal foil VHP type.

See the link, there is a pic of the resistor, it's open, no protection
at all.

>
> Besides electrical measurement (on OHM range!), I 'd recommen  
> optical inspection of the case, and if its possible, of the windings  
> for burnt/overheated areas. Corrosion may be easily identified, also  
> by slightly stained parts of the wire.

yes, the low valued resistors (10/20 ohm) seem a little corroded.
The intermediate valued ones seem ok.

Is the wire used (manganin?) prone to corrosion?

Fabio.

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