Hi Everyone,

I have a problem. I bought a Solartron 7071 on Ebay.
That Voltmeter seems working properly but I think it's too noisy.
It passes Self Test and Initialize and the reading is consistent against
a Weston Cell to the µV.
But, when left with a short circuit as input the noise (maximum during 5
min) is:
0.2µV for 0.1V scale
0.4µV for 1V scale
8µV for 10V scale

Is it acceptable?
Thanks for your help.

Bye,
Jean-Louis

Solartron 7071/7081 manuals don't have official information about the
measurement noise. So I don't understand where "0.1/0.6/4 uV" is coming from.
Only one of the docs - Instruments Test Specification - have a 10 V noise limits:
"10 V noise - The rms noise of 10 readings at 10 V is measured. It must be less
than 3 uV". This is roughly equal to 12 uV p-p (with p=0.998, f=10).
My old measurements (7.5-digits, short, 5-10 minutes):
0.1 V = 0.2 uV
10 V = 5 uV
Solartron 7071/7081 have a several main sources of short-term instability. From
most important to least:

1. Improper settings of the PLL's nominal frequency (see page 9.5 of the Service
   Manual).
2. Noisy 1N829 Zener.
3. Noisy IC201 (swap to LTC1052 solves this problem forever).
4. Noisy Input Amplifier.

Regards,
Mickle T.

Tuesday, July 22, 2014, 8:19:25 PM, you wrote:
JLN> Hi Everyone,

JLN> I have a problem. I bought a Solartron 7071 on Ebay.
JLN> That Voltmeter seems working properly but I think it's too noisy.
JLN> It passes Self Test and Initialize and the reading is consistent against
JLN> a Weston Cell to the µV.
JLN> But, when left with a short circuit as input the noise (maximum during 5
JLN> min) is:
JLN> 0.2µV for 0.1V scale
JLN> 0.4µV for 1V scale
JLN> 8µV for 10V scale

JLN> Is it acceptable?
JLN> Thanks for your help.

JLN> Bye,
JLN> Jean-Louis
JLN> _______________________________________________
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JLN> and follow the instructions there.