John,
Your right. When I wrote this, I was using an app called ESBcalc on my computer
and I did it wrong. I was used to using my hand calculator, and this app is
different in the way you do it. Sorry for the confusion. I need to read over
what I type more often. Those resistors at 0.01% would be ok, and the same as a
standard. At $7 a piece though, I need to find where to buy them that cheap.
Most I have had quoted to me were way more than that.
Best,
Will
*********** REPLY SEPARATOR ***********
On 4/23/06 at 3:02 PM W0UN -- John Brosnahan wrote:
>>
>> >0.01% resistors are pretty cheap. I use them in projects some times when
>> >I want accuracy. Converting from pounds to USD, I reckon they are about
>> >$7. Not exactly expensive and quite within the range of a ham to own a
>> >few. Hence I somewhat doubt there is much point selling resistance
>> >standards.
>> >
>>
>>
>>The 0.01% is a guaranteed value of resistors and standards, Most
>>standards though are actually closer than that by a good size amount
>>because they have been calibrated against a NIST traceable standard.
>>Most standard resistors were hand wound at one time. General Radio
>>and ESI both had resistor departments. The 0.01% resistors off the
>>shelf can vary up to that percentage. At 10k ohms, that's +/- 100
>>ohms. A standard that has been calibrated is actually much closer,
>>within 1 to 5 ohms at 10k ohms from what I have seen (9995, etc. 0r
>>0.0005%). A 5-1/2 digit DMM will read that easily. Over 99.9k ohms,
>>you need to go on up to a 6-1/2 or 7-1/2 digits to see the smaller
>>scale. A calibrated standard though will hold the guaranteed value
>>over the entire resistance it's capable of. If you placed in series
>>a bunch of off the shelf resistors together at 0.01%, I doubt you
>>could get that close.
>
>
>A 0.01% 10K resistor can only vary by +/- 1 ohm and meet specs.
>
>1% = 1/100
>0.1% = 1/1000
>0.01% = 1/10,000
>
>1/10,000 of 10,000 ohms is 1 ohm
>
>--John
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