Can you use an Agilent 34401 DVM as a Waveform Digitizer?
EDN Has published an article written by me this very subject,
"Use a DVM to directly digitize low-frequency noise (Part 1 and 2)"
The project I was working on involved measuring 0.1 to 10 Hz noise not only for RMS and peak-to-peak values in the time domain, but using an FFT Analyzer in the frequency domain also. I was all ready to get out a bunch of equipment and make a special test fixture, but then I remembered that my Agilent 34401 can make readings very fast and I set about exploring what can be done with just the meter itself.
When we think of DMM's we normally think of measuring very slowly moving DC signals. This month takes a look at what performance can be acheived, Next month we will take a look at how to verify the performance of our DVM as a Waveform Digitizer.
Steve Hageman
www.AnalogHome.com
This is a fascinating concept, for engineers who are interested in ultralow-frequency noise measurement.
ReplyDeleteDoes the Agilent Meter directly write over a USB cable to a file inside of a PC? Something like downloading a camera ?
I have a lab set up to measure LF noise, however I was shut down when my expensive recording voltmeter blew. The recording VM had a 24-bit A/D, because the the input pedestal was allowed to range over -2.5V to +2.5V. However the input noise floor was less than 10uV rms.
Since I began to measure LF noise, I have found ways to shift any offset signal to a zero-volt pedestal. This would allow me to settle for much lower resolution in the recording VM. (16 bits)
I have looked at the idea of 'tricking out' an audio spectrum analyzer to work at 0.001Hz and 20 samples/sec, however this is not practical.
If I can get the voltmeter data into a file, I can parse the data to get to 20 samples/sec (8Hz BW), and then look for an inexpensive FFT program which will accept my data.