Author Topic: Wanted: 0.1 ohm 0.1% 10 W Resistor  (Read 3592 times)

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Offline requimTopic starter

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Wanted: 0.1 ohm 0.1% 10 W Resistor
« on: October 21, 2011, 10:26:14 am »
The HP/Agilent e3610a DC Power Supply requires this resistor for calibration, however I've searched the top 5-6 websites (digikey, mouser, etc) and can't find even a whiff of the part even existing.  Any ideas?
 

Offline amspire

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Re: Wanted: 0.1 ohm 0.1% 10 W Resistor
« Reply #1 on: October 21, 2011, 11:16:42 am »
You don't need it. Just use the 20A current range on your multimeter.
 

Offline ejeffrey

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Re: Wanted: 0.1 ohm 0.1% 10 W Resistor
« Reply #2 on: October 21, 2011, 12:34:09 pm »
Get a 1% accurate unit and measure the exact resistance with an accurate meter or get several lower power parts and parallel/series connect them to reach the power rating.

Or, do what amspire says and just use a calibrated current meter rather than a precision load.
 

alm

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Re: Wanted: 0.1 ohm 0.1% 10 W Resistor
« Reply #3 on: October 21, 2011, 04:00:43 pm »
Note that the resistance will change as you increase the current due to heating of the resistor. This may be more than 0.1% depending on the temperature rise.
 

Offline ciccio

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Re: Wanted: 0.1 ohm 0.1% 10 W Resistor
« Reply #4 on: October 21, 2011, 05:52:53 pm »
Why not 10 x 0.1% 1 ohm / 1W resistors in parallel?
Maybe they are easier to find (not sure, I've searched a little and found only expensive  one, limited to 0.33 W).
regards
Strenua Nos Exercet Inertia
I'm old enough, I don't repeat mistakes.
I always invent new ones
 

Offline ejeffrey

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Re: Wanted: 0.1 ohm 0.1% 10 W Resistor
« Reply #5 on: October 21, 2011, 06:20:55 pm »
One thing about rolling your own:  .1% of 0.1 ohm is 100 microohm.  Obviously this is an order of magnitude less than contact resistance so you will need a 4-point kelvin connection.  A commercial precision current sense resistor will have this done correctly.  However, at this level spreading resistance and lead resistance are also significant.  If you build a composite resistor from multiple lower power devices you will need to ensure you do so in a way that limits these sources of error.  Of course, you can just measure the resistance with an accurate resistance meter, but if you have a sufficiently accurate ohm meter you can just take a 10W 1% resistor and measure that.
 


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