Author Topic: What brand precision BMF resistor is this? What Can I Build?  (Read 783 times)

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Offline denimdragonTopic starter

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What brand precision BMF resistor is this? What Can I Build?
« on: March 26, 2024, 06:08:46 am »
I had a datasheet on these but I have since then misplaced it  :palm:

Does anyone know what brand this is? I recall that they had been bought
out by Vishay a while back. They are spec'd pretty good. I have tons,
but only one value 3118 ohms. I would also love any suggestions of
what piece of precision test gear I could make. A nice voltage divider
comes to mind  :popcorn:2084822-0
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Offline denimdragonTopic starter

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Re: What brand precision BMF resistor is this? What Can I Build?
« Reply #1 on: March 26, 2024, 05:36:48 pm »
So, no one who has viewed this thread, is familiar with this
resistor brand?

 :-//

Well, I have been logging them with my 34970A and my freshly
Cal'D (  :-DMM :-+ yeap, I have been bitten by the v-n bug) 34401A
over a 6 hour period @ 24°C ±2°C (no RH yet, but the lab is located
at the highest part of the house so...) and they have performed extremely
well (≅<1ppm/°C).

Maybe I have posted this in the wrong forum. Mods, let me know.

 :popcorn:
 
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Offline Victorman222

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Re: What brand precision BMF resistor is this? What Can I Build?
« Reply #2 on: March 26, 2024, 06:22:10 pm »
My google-fu lead me to Wilbrecht ledco. Check out:
https://web.archive.org/web/20120108085924/http://www.wilbrechtledco.com/produits/foil.html
Luckily even the datasheets are archived.
 
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Offline trobbins

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Re: What brand precision BMF resistor is this? What Can I Build?
« Reply #3 on: March 27, 2024, 03:50:03 am »
Hammon dividers and bridge always need good precision resistors, and you could go the next level and sort what you have for value and tempo.
 
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Offline donlisms

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Re: What brand precision BMF resistor is this? What Can I Build?
« Reply #4 on: March 27, 2024, 05:14:56 am »
Three of them in series plus 646 ohms makes 10k. I don't know what that might mean, but it seems interesting.
 

Offline denimdragonTopic starter

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Re: What brand precision BMF resistor is this? What Can I Build?
« Reply #5 on: March 27, 2024, 11:38:23 am »
Hammon dividers and bridge always need good precision resistors, and you could go the next level and sort what you have for value and tempo.

This is what had in mind. I started logging them a couple of days ago
with one of my HP 34970A 6 resistors at a time. My question here is,
how long should I monitor them to get a reasonable estimation? Should
it be for 1K hours or can I get away with less? According to the datasheet, the TC is ±2.5ppm.
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Offline trobbins

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Re: What brand precision BMF resistor is this? What Can I Build?
« Reply #6 on: March 27, 2024, 12:19:27 pm »
I would have thought just some simplified binning for starters based on a gross temp shift of say 5 degC to see what distribution of tempco's occur.  If you easily identify pos and neg levels of tempco then you could match pairs of similar pos and neg tempco's, as what Fluke (and I guess many others) did.
 
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Offline denimdragonTopic starter

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Re: What brand precision BMF resistor is this? What Can I Build?
« Reply #7 on: March 27, 2024, 01:49:45 pm »
I would have thought just some simplified binning for starters based on a gross temp shift of say 5 degC to see what distribution of tempco's occur.  If you easily identify pos and neg levels of tempco then you could match pairs of similar pos and neg tempco's, as what Fluke (and I guess many others) did.

Yes, matching the TC drift direction is the most critical aspect. I have
about 400 of this particular value so I should be able to come up with
some nice matches. I'm setting up the modules for 4W measurements
now so I can get the process going. These 34970As are so awesome
for this process. They are so underrated.

I also need the exact datasheet for this "YT" series. I have datasheets
for the WA WB & WQ WT, but no YT.
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Offline Victorman222

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Re: What brand precision BMF resistor is this? What Can I Build?
« Reply #8 on: March 27, 2024, 06:33:06 pm »
I also need the exact datasheet for this "YT" series. I have datasheets
for the WA WB & WQ WT, but no YT.

These resistors are probably WA or WB or their predecessors as they have same marking style as in datasheet. YT is marking where Y is tempco and T is tolerance (0.01%), but that datasheet doesnt have any info on "Y" tempco code..

« Last Edit: March 27, 2024, 06:38:30 pm by Victorman222 »
 

Offline Andreas

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Re: What brand precision BMF resistor is this? What Can I Build?
« Reply #9 on: March 27, 2024, 07:51:48 pm »
Hello,

Y usually stands for +/-2.5 ppm/K
see for example FLCY resistors from ALPHA

with best regards

Andreas
 
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