[TangerineSDR] Fwd: How do you feel about my forwarding your results to other users?

[David Witten]

---------- Forwarded message ---------
From: Julius Madey <hillfox at fairpoint.net>
Date: Tue, Jul 28, 2020 at 8:13 PM
Subject: Re: How do you feel about my forwarding your results to other
users?
To: David Witten <wittend at wwrinc.com>


Dave.

Here's the first couple of pieces on temp sensitivity.  Considering the
full range of the RM3100, the observed effect could be considered
relatively small. However, it's in the region we need to observe.  Although
the basic idea of taking the differences in duty cycle of the LR oscillator
with forward and reverse bias eliminates some major temperature
contributions, it apparently does not totally eliminate them.

One is of a GTJ run on 07072020 and the other a one hour calibration run I
did yesterday 07272020.  Note the reversed sense of the temperature change
effect.  I have a second RM3100 which I will also run in the next few days
for comparison.  I used your original adapter board.  The setup in the wood
lot at the end of 400 feet of CAT5E I believe uses the same adapter board
you supplied to Hyomin.  Reducing the 24 hour data in Open Office Calc took
a god-awful time to complete.

Feel free to distribute these ...  I'm going to send them to PNI for their
comment.  I did not attempt to measure the drift, if any, of the 3.3 volt
regulator output on the SparkFun i2c differential extender at the test
end.  I also have data which was taken with a delay between the start
command and looking at the Status register to keep the i2c bus quiet during
measurement and the trends are the same.  I don't think PC trace currents
created that much local field but that's another check for the future.

Jules


> Julius Madey
> [image: Attachments]Tue, Jul 28, 11:15 AM (21 hours ago)
> to me
> Dave,
> I have no problem with sharing that my tests so far have shown that, at
> least on the y axis which was tested,  the RM3100 is well within 5%
> accuracy with Helmholtz coil excitation with a long period (30 minutes to 1
> hour) sine wave of +/-50, +/- 524 and +/- 2893 nT.   And I would be happy
> to provide graphs to the repository.
>
> My problem at this point is incomplete data on another aspect, which is
> why I haven't released the stuff I mentioned yesterday.
>
> PNI claims that the basic measurement technique employed in the RM3100
> eliminates temperature effects.  See the attached note.
>
> However, I am clearly seeing what appear to be temperature related effects
> in the measurements, at least at lower levels like 30 to 150nT variations
> of the sort seen at the Jenny Jump tests.  If you know the tempco, it's
> possible to compensate in the data reduction ..... however......the
> disconcerting thing is that I'm seeing different trends vs temp in the GTJ
> results and the runs I did in the last couple of days.  Tempco sign
> differences, which suggests magnetometers may have to be calibrated before
> deployment ...  temperature variations of 15 C or more
>
> If I look at the temperature related effects of the GTJ measurements
> (tedious work due to the large data set) it appears that the significant
> deviation which Hyomin noted between the GTJ and JJ data is entirely due to
> temperature variations over the 24 hour runs  !!
>
>
> I have an inquiry in to PMI.
>
> Jules
> Attachments area
>
>
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