12-13-2006 02:20 PM
12-14-2006 01:50 PM
12-14-2006 02:04 PM
I appreciate the response but I'm really looking for somebody who knows what goes into the toolbox and how that would compare to a more traditional spec analyzer. The manual talks about meeting 'ANSI S1.11-1986, Order 3, Type 1-D, optional range' for the filter specs. I'm confident that the routine is scaled correctly etc because I can run a cal signal through it (159 Hz at 1g) and get the correct 120 dB ref 1 micro g.
On the issue of averaging, I can't argue. The spec analyzer only takes 16 s but doesn't talk about averaging over this time period. It definately averages when we perform narrow band measurements because you can set that up with the user interface screens.
Maybe I'l just try taking the 1st 16 sec of data and compare those two data sets.
If I don't get any other response, I'll get back to you.
Thanks,
Frank
12-14-2006 02:22 PM
12-15-2006 07:11 AM
12-18-2006 09:10 AM
Neil,
Here are the things I know -
I'm using one of the SVT examples,
the HP is using the ANSI S1.11 - 1986, Order 3, Type 1-D filters (same as LV), now weighting for these tests (we use it for airborne noise), don't know about averaging but the manual talks about 'a 2 second stable average'
my acquisition rate of 50kHz (2.5 x 20kHz) was not fast enough with a true center frequency of 20158.74 Hz desired,
I'm concerned about anti-aliasing - HP has it, I hadn't worried about it yet,
16 s worth of my 48 s didn't matter (see attached Excel file) - there are two sets of data in the workbook, noise data (Chart 1) and calibration data (Cal) the file shows that by about 800 Hz the two solutions diverge, converge, and diverge again,
I've also attached a couple of screen shots from the routine showing the 1/3 octave plot and the scaled time series data. The primary noise is coming in at around 7 Hz - showing up in the 10 Hz bin. The magnitude agrees reasonably well with the HP but I'm concerned about the linear rise in the reported levels at the ferquency goes up.
I've got some more homework with the HP to figure out what it is and isn't doing...
Any ideas?
Frank
12-18-2006 09:42 AM - edited 12-18-2006 09:42 AM
Message Edited by Neil S. on 12-18-2006 09:42 AM
12-18-2006 09:57 AM
12-18-2006 10:11 AM
12-18-2006 10:25 AM