[volt-nuts] Fluke 332B
kc9ieq at yahoo.com
Mon Feb 20 16:10:50 EST 2017
Very interesting. What series resistor did you have these results with? Very interested to compare spec'd temp co.
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-------- Original message --------From: Jerry Hancock <jerry at hanler.com> Date: 2/20/17 2:51 PM (GMT-06:00) To: kc9ieq <kc9ieq at yahoo.com> Cc: Discussion of precise voltage measurement <volt-nuts at febo.com> Subject: Re: [volt-nuts] Fluke 332B
I took some of the 100K 1/4 watt resistors from my DAS-46 and heated them with a soldering iron. They ran high pretty quickly. I then used a cheap, 1% Chinese brand metal film and they ran high just about as quickly. The 5% Chinese brand ran low a lot faster. Just bringing the soldering iron near them Interesting in that using one of each, the resistance stayed about right on the parallel value. I then used a high quality Vishay and I couldn’t get it to move with the soldering iron without touching it. These resistors cost about .40 per at Mouser. I was just using my Agilent DMM so I’m sure they were moving, just not within the resolution of the meter. The bottom line is that the carbon comp I replaced with the 50 cent per Vishay was a good move. Had I used the 5% I have, it would have been about the same.
> On Feb 20, 2017, at 12:36 PM, kc9ieq <kc9ieq at yahoo.com> wrote:
> Very interesting, very curious to hear your conclusion!
> My thought would be to replace these with standard value 5% resistors having good temp co, as calibration should surely make up for any subpar values-- my thinking is that temp drift would be a more major consideration for overall stability. If this is a false assumption of would certainly like to learn why.
> Perhaps the old Allen Bradley carbon comps were special in this regard, but the data sheet I've seen for currently available comp resistors had a horrible temperature coefficient-- much worse than the "better" film resistors available today. I stock the Vishay PR02 metal films for rebuilding old tube stuff, which have a temp comp of +/- 250ppm/K. There are much more stable options out there, but I chose this line because of the 500V rating and dark red/brown color which blends into an old chassis more so than tan or bright blue.
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