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Specified Resolution for an instrument

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sayakghoshal
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Joined: June 28th, 2013, 5:41 am
Country: Turkey

Specified Resolution for an instrument

Post by sayakghoshal » June 28th, 2013, 6:17 am

Hi
I have a basic question about the resolution of the Keithley voltmeters and multimeters. Like 2182 has resolution of 1nV, 2700 has resolution of 100nV at their best ranges. What is meant by this resolution? Is it the ADC resolution or fluctuation about the mean or something else?

What about the data collected? It generally can give more precision than the resolution? Upto what precision it is reliable?

Also I have read in different articles that averaging can increase resolution (although i am not totally convinced yet). So now if I do 100 measurements and do averaging then can I say that my 2700 measurement has better than 100nV resolution (Lets consider the ideal condition that there is no drift in the signal voltage and all other things are ideal). Can you also please explain me the reason. I am really confused between increase in resolution and decrease in noise.

If you can clarify all of the above mentioned points it will be very helpful.

Dale C
Keithley Applications
Keithley Applications
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Joined: June 10th, 2010, 6:22 am
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Re: Specified Resolution for an instrument

Post by Dale C » July 1st, 2013, 8:40 am

Resolution is number of digits. 5 1/2 , 6 1/2 and so on.
Sensitivity is the smallest amount of signal that can be detected on a range.
For example on a 6 1/2 digit voltmeter on the 1V range.
The resolution is 6 1/2 digits (0.000000).
The sensitivity is 1uV. (0.000001).
The accuracy is different.
On the Model 2700 on the 1V range it can detect to 1uV but is accurate to about 7uV.
On the Model 2182A on the 1V range it can detect 100nV but is accurate to about 2uV.
The Model 2182A really helps with lower voltage signals.
On the Model 2700 on the 100mV range it can detect to 100nV but is accurate to about 3.5uV.
On the Model 2182A on the 100mV range it can detect to 10nV but is accurate to about 0.4uV(40nV).
This is about 10 times better.
Averaging helps reduce noise.

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