[volt-nuts] More Precision Resistors

[Mark Sims]

I recently got in an ESI DB877 8 decade resistance box (12 Megohms at 0.1 ohms/step).   This box is chock full of 0.01% wire wound resistors (1R and 5x2R resistors per decade) and a pair of nested four gang switches/dials.

The 1K resistor was pretty much toast.  I replaced it with the 900.98 ohm and 100.02 ohm resistors from a Tektronix 067-0503-00 precision DC divider (paralleled with a selected 1 Meg resistor).  That resistor is now within around 0.0005%.

The 10K resistor was also off,  reading around 10015 ohms.  Paralleling it with a selected resistor pair also got it to around 0.0005%.

All is well with this wonderful little box and all values are now well within spec (0.01%).   Most are under 0.003%.  However,  things could be better for this volt nut.  The 100K and 5x200K resistors are all around 8-9 ohms high.  

Does anybody know of a cheap source of 1 to 5 gohm  resistors (actually 1.250 gohm,  1x2.500 gohm,  and 4x4.000 gohm,   would be best and would get that whole decade under 0.001%)?  Mouser/Digikey/etc have them for around 4 bucks a pop... cheaper is better...

Now,  if I could also find a -0.0382 ohm resistor to cancel out the zero ohm lead/switch bias...

----------------------------------------


_________________________________________________________________
Windows Live™: Keep your life in sync.
http://windowslive.com/explore?ocid=PID23384::T:WLMTAGL:ON:WL:en-US:NF_BR_sync:082009