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Low AC voltage measurements

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magsci
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Joined: October 22nd, 2012, 12:43 pm
Country: United States

Low AC voltage measurements

Post by magsci » October 22nd, 2012, 12:55 pm

Which instrument will provide the lowest possible AC voltage measurement around 40 to 70 Hz, and how low is the voltage that can be measured? My source has impedance probably in the kohms or Megahoms, and I want to measure the open-circuited AC voltage across the output terminals of the source.

Dale C
Keithley Applications
Keithley Applications
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Re: Low AC voltage measurements

Post by Dale C » October 22nd, 2012, 1:54 pm

Model 2001 can read to 0.1uV on ACV. But can get to 2mV accurately. That is where the spec starts.
The impedance is 1M Ohm on ACV.

rahulsingh
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Joined: January 26th, 2015, 8:41 am
Country: India

Re: Low AC voltage measurements

Post by rahulsingh » January 26th, 2015, 8:44 am

Dear Dale,

I want to measure 5 - 30 micro Volt AC preferably peak voltage. Which instrument I can use to measure this.

Regds
Rahul

Dale C
Keithley Applications
Keithley Applications
Posts: 2840
Joined: June 10th, 2010, 6:22 am
Country: United States
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Re: Low AC voltage measurements

Post by Dale C » January 26th, 2015, 11:07 am

All Keithley DMMs have a sensitivity of at least 1uV on ACV.
But the accuracy is as I described in the earlier email.
The best ACV sensitivity and accuracy from Keithley is the Model 2001.
But the accuracy is about to 1 of range which on the 200mV range is 2mV.
What is the frequency of the signal you are trying to measure?
Maybe you could use a fast DMM on DCV to capture a number of points on the wave.
Example:
If it is a 100Hz signal, then you could take 100 readings at a 1kHz rate. That would give you 100 points in the wave.
You could calculate the rms value from there.
Most of the DMMs can take a burst of data at this speed.

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