[volt-nuts] Solartron 7081 Test Leads

[Bill Ezell]

Joe, If you don't have a cal key, the switch form-factor is standard. I 
just replaced the switch on my 7081. If I remember correctly, the part 
number isn't the same, but the mfgr is. I ordered from Digikey.

Who did you order the Fischer connectors from? I tracked down part 
numbers a few years ago, but couldn't find anyone to actually sell them 
to me. I found one at a flea market, and I did snag two original cables.

Regarding the cables/probes, there were several models. The most common 
have two banana plugs. The connection thru the cable is true 4-wire, 
terminating at the plug. There was also a version with 5 plugs (4-wire 
plus shield), and a version with a pair of Kelvin clips (the real ones, 
one of each pair to each side of the clip).

You don't need a Kelvin connection for anything other than resistance 
measurement. The meter does quite well with the 2-plug version for that 
anyway.

I used 5-wire + shield PTFE / pure copper (picked up on EBay, lots of 
mil-spec cable shows up there, mostly from aerospace leftovers) 
terminated with Pomona low-emf plugs.

BTW, these are really great meters (except for the read time at 8.5 
digits!). Mine keeps cal within typically 1 or 2 ppm for over a year at 
a time. Yes, seriously. I compare it periodically to my 
(Fluke-calibrated) pair of Datron 4910 references, and almost never have 
to recal. (Another wonderful piece of equipment, the 4910).
Nice thing about all these old pieces of equipment, they're usually well 
down the aging curve. :)

One thing, they really take 24 hours to fully stabilize, so let it run a 
few days if you're going to calibrate it.
Have you checked out the voltage ref it uses? Amazing.It's just a 
non-ovenized Zener, albeit one that was designed to be a ref (the 
still-available 1N829A). The Zener itself is good to about 5ppm/C. 
Solartron then calibrated each one to find the inflection point on its 
voltage/temp curve. The meter has a DAC that sets the current to be at 
that point. Then, they add a non-linear temperature-dependent 
compensation voltage to eliminate even more tempco. If you look at the 
Chinese meter review referred to by other posters, you can see how it 
compares to the HP. Pretty impressive.

One more thing, read your cal constants! The critical one is the Zener 
bias setting. If you lose the EEPROM, that one would be very difficult 
to determine again. The rest can be recovered by a recal.

On 08/04/2011 01:13 PM, volt-nuts-request at febo.com wrote:
> Solartron 7081 Test Leads...

-- 
Bill Ezell
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They said 'Windows or better'
so I used Linux.