[volt-nuts] Resistance standard

Mark Sims holrum at hotmail.com
Tue Dec 15 19:22:04 UTC 2009

I just got in an ESI SR104 10K resistance standard...  widely considered the best resistor around.   It was designed in the 60's and is still manufactured today ($7K+ for a shiny new one,  there is (always) one on Ebay for $3K,  but the ones that sell fetch around $1200-$1500.  One just sold in the UK for dirt cheap,  mine was about half the going rate)  

This device is two resistors in an hermetically sealed oil bath.  One is the precise resistor and the other is a 1000 ppm tempco resistor used as a thermometer.   

I wrote a computer program to calculate the precise value from the calibration constants.  The chart in the lid is not up to the task and their manual is woefully inadequate/ambiguous when it comes the task of calculating the exact resistance.

Right now it is reading 9999.996 ohms on a HP 3458A (should be 9999.998,  but the room temp is 60F,  out of their +/- 5C spec range).

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