Author Topic: 9Mom resistance reference.  (Read 1370 times)

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Offline Samogon

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9Mom resistance reference.
« on: June 15, 2016, 12:10:07 pm »
Hello,
Recently i have scored two Agilent 34401A DMMs (and absolutely love them), one was sold for part or repair with description that 10MoM range has significant error.
I have tested it and was not able to find any diviations from other 34401A measurments.
But i have tested it on 1/4w 5% carbon resistors. Reading were consistent among both 34401A anb my trusted Fluke 289.
Anyway i found that input resistors of oscilloscope are very precise on my Agilent DSO5054A there are two 0.4993 MoM in series. Then i concluded that probes have to have equal or better precision 9MoM resistor in them, and it looks like it is true. I have measured two Agilent N2890A probes and they show pretty close resistance of 9.029 and 9.000  MoM.
Can we say that there is high tolerance resisters used in scope probes?
Asking it that i was not able to find any at least 0.1% tolerance resistors of MoM range.
Anybody knows what types of resistors used in high quality probes? And can we rely on those to test DMMs?
« Last Edit: June 16, 2016, 04:10:52 am by Samogon »
 

Online Vgkid

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Re: 9Mom resistance reference.
« Reply #1 on: June 15, 2016, 03:47:45 pm »
The scope probe resistors could be Caddock's(might be to expensive, they could use multiple smaller resistors). Instead of a 9.0Meg resistor, use a 10M resistor. For a precise one a Caddock USF will work.
If you own any North Hills Electronics gear, message me. L&N Fan
 
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Offline Samogon

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Re: 9Mom resistance reference.
« Reply #2 on: June 15, 2016, 05:48:40 pm »
Yeah, 20M .01%  $41 on digikey  :)
 

Online Vgkid

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Re: 9Mom resistance reference.
« Reply #3 on: June 16, 2016, 03:26:38 am »
10Meg is what you need. A 0.01% should be about$ 20.00.  You don't need to buy the 20Meg unless you plan on putting two in parallel. A 20Meg resistor will kick you into the 100M range, which that ranges accuracy gets measured in percent.
If you own any North Hills Electronics gear, message me. L&N Fan
 
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Offline RobK_NL

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Re: 9Mom resistance reference.
« Reply #4 on: June 16, 2016, 06:11:30 am »
my trusted Fluke 289.
So, there's your 10Meg reference  :)
Tell us what problem you want to solve, not what solution you're having problems with
 

Offline Samogon

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Re: 9Mom resistance reference.
« Reply #5 on: June 16, 2016, 06:30:21 am »
my trusted Fluke 289.
So, there's your 10Meg reference  :)
You mean DMMs voltage input resistance is 10Megs? It measures 11Megs
 

Online Vgkid

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Re: 9Mom resistance reference.
« Reply #6 on: June 16, 2016, 07:07:08 am »
That would work as a comparasion between 2 similiar meters. The 34401A is 12.000,000 counts, so the 11M would be at the top of the scale.  Wouldn't rely on it for precision, as you are dealing with the leakages associated with its input protection circuitry.
If you own any North Hills Electronics gear, message me. L&N Fan
 

Offline Samogon

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Re: 9Mom resistance reference.
« Reply #7 on: June 16, 2016, 07:20:47 am »
Agree, and good to have to similar (better tree) DMMs comparison gives confidence in readings. It is unlikely that two meters would give exactly same level and sign of deviation.
Convinced to order caddock 10Meg
 


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