[TangerineSDR] Fwd: another 24hour RM3100 run and comparison with Fredericksburg

Kim, Hyomin hmkim at njit.edu
Mon Oct 5 17:31:25 EDT 2020

Hi Dave, Jules and Nathaniel,
Sorry that it took me so long to work on the data that was retrieved from
Jenny Jump. The two sensors (Bartington and our mag) were placed inside a
solenoid which was then placed inside a mu-metal case. Long story short,
there is NO reason to believe that our magnetometer behaves in a different
way compared to the other. They trace the artificially generated fields
well. The only thing that needs to be addressed later is that the given
field was so big that the output signals were saturated - the fields inside
the solenoids should have been decreased to avoid saturation. My oversight
that I had to leave the site in a rush. However, both sensors traced the
fields in the same way. I hope I will have more time to stay at Jenny Jump
next time to monitor the signals more carefully as the NJIT system has now
been fixed.

Please share this during the Tangerine meeting tonight as I will not be
able to attend it this time due to the conflict with my lecture which is
expected to be longer than last week...


[image: NJIT logo] <https://www.njit.edu/> *Hyomin Kim*
Assistant Professor
Center for Solar-Terrestrial Research
Institute for Space Weather Sciences
hmkim at njit.edu • (973) 596-5704
104 Tiernan Hall, 161 Warren Street, Newark, NJ 07102

On Tue, Sep 22, 2020 at 9:45 PM Julius Madey via TangerineSDR <
tangerinesdr at lists.tapr.org> wrote:

> Dear John,
> Yes, temperature information was posted a while back.  PNI initially
> claimed that there was no temperature effect due to the essentially self
> compensating scheme used for field measurement. After I measured as much as
> a 7-10nT per degree C tempco in some controlled oven experiments and
> sharing that data with PNI, PNI eventually replied that engineering had
> measured a maximum of +/- 2nT per degree C for the inductors alone but had
> not characterized the complete sensor.
> The data I have taken so far is not complete but indicates that the tempco
> (1) may not be equal on all axes, including differences in sign and (2) may
> not be assumed to be equal for any two units and (3) may not be linear with
> temperature, making algorithmic correction of the recorded data difficult.
> Hence, my attempts to achieve temperature stabilization to better than 1
> degree C over 24 hours for the recordings I've been doing (sensor in a
> housing that can be easily buried sub surface).
> Have also done some experiments with an insulated chamber containing a
> thermal mass, equivalent to a low pass filter, to achieve stabilization.
> Another approach is a temperature controlled oven set to a few degrees
> above expected maximum local ambient temp but that requires power, which
> complicates long cable runs.
> At just 19-20 inches below grade in my shaded woodlot, 24 hour temperature
> stability has been within 0.7C.  Another 12-16 inches for the next install
> should bring that to a diurnal variation of perhaps 0.1C in this location.
> Jules K2KGJ
> On 9/22/2020 7:52 PM, John Gibbons wrote:
> All,
> I have not kept up on this thread due to other commitments, but I don't
> see any mention of the temperature data and plotting correlated to the data
> acquisition of the 3 axis magnetometer (or more likely I missed it).
> I believe that the RM3100 uses ferrite core inductors for the 3 axis
> magnetic pickups and ferrites definitely have a tempco (voice of
> experience...). Even a 1 Deg C may have an impact on the mu of the ferrite
> at the 1nT measurement levels.
> You've probably already done this (if so please point me to it) but has
> this been looked at / tested for / quantified?
> John N8OBJ
> John C. Gibbons
> Director - Sears Undergraduate Design Laboratory
> Dept. of Electrical Engineering and Computer Science
> Case Western Reserve University
> 10900 Euclid Ave, Glennan 314
> Cleveland, Ohio  44106-7071
> Phone (216) 368-2816 <216-368-2816> FAX (216) 368-6888 <216-368-6888>
> E-mail: jcg66 at case.edu
> On Mon, Sep 21, 2020 at 4:18 PM Julius Madey via TangerineSDR <
> tangerinesdr at lists.tapr.org> wrote:
>> Forgot to mention that one thing to keep in mind is the difference in raw
>> data processing between the absolute value sliding 1minute average plots I
>> do with a spreadsheet with the more complex algorithm delta B plots from
>> Intermagnet.  I'm not sure how the 10nT anomaly would appear if the same
>> Intermagnet processing algorithm was used.
>> Hyomin ?????
>> On 9/15/2020 10:38 AM, Phil Erickson wrote:
>> Hi Dave,
>>   The X and Y traces return after 24 hours to nearly the same relative
>> value in both the reference and RM3100 traces.  The Z trace does not.
>> Ionospheric currents flowing in the E region should not affect Z exclusive
>> of X and Y under most any geometry I can think of, so I wondered whether
>> the uncalibrated RM3100 was likely causing this.  (I have never
>> professionally calibrated a magnetometer, so Hyomin might need to comment
>> here.). In other words, I always assume there is some measurement
>> systematic until it has been completely ruled out before assigning it to
>> geophysical variation.
>> 73
>> Phil W1PJE
>> On Tue, Sep 15, 2020 at 10:34 AM David Witten <wittend at wwrinc.com> wrote:
>>> @Phil,
>>> Correlation is great, and surely some further calibration issues may
>>> remain.  But these sensors are NOT colocated - (200-300+ mi apart?) .
>>> Wouldn't it be suspicious if they did correlate perfectly?  If they did,
>>> shouldn't  we ask if we do really need an extensive array of these
>>> sensors?  Presumably there will always be some local variation at this
>>> scale?  (don't know, just asking)
>>> Dave Witten, KD0EAG
>>> On Tue, Sep 15, 2020 at 7:21 AM Phil Erickson <phil.erickson at gmail.com>
>>> wrote:
>>>> Hi all,
>>>>   There appears to be a 10 nT drift in the Z component for the RM3100
>>>> that is not in the Fredericksburg traces.  Is that slow systematic bias
>>>> expected?  Maybe things are not calbrated over that time frame quite yet?
>>>> 73
>>>> Phil W1PJE
>>>> On Mon, Sep 14, 2020 at 10:49 PM David Witten via TangerineSDR <
>>>> tangerinesdr at lists.tapr.org> wrote:
>>>>> I don't believe that my previous post carried the file K2KGJ provided.
>>>>> ---------- Forwarded message ---------
>>>>> From: Julius Madey <hillfox at fairpoint.net>
>>>>> Date: Mon, Sep 14, 2020 at 4:26 PM
>>>>> Subject: another 24hour RM3100 run and comparison with Fredericksburg
>>>>> To: Kim, Hyomin <hmkim at njit.edu>, David Witten <wittend at wwrinc.com>,
>>>>> Dr. Nathaniel A. Frissell Ph.D. <nathaniel.frissell at scranton.edu>,
>>>>> Dave Larsen <kv0s.dave at gmail.com>
>>>>> All,
>>>>> I was hoping to record a relatively short term event but missed one
>>>>> about 10 days ago.  However, there was a good run on the 12th with an ~30nT
>>>>> excursion on the Y axis lasting about an hour.  In the attached pdf, the
>>>>> three axes of the RM3100 again track the Fredericksburg magnetometer
>>>>> station data quite closely.  The RM3100 plotted data points are simple
>>>>> running 60second averages and not the more complex filtering algorithm used
>>>>> by Intermagnet stations for their 1 minute data points.
>>>>> The vertical axes scales on all plots are as close as I could match
>>>>> them by eye in cutting and pasting.
>>>>> I believe the value to the right on the Intermagnet plot is the mean
>>>>> for the 24 hour period.  I did not try to compute a 24 hour mean.
>>>>> One of the products for the future for general interest would be a
>>>>> running plot like those available on Intermagnet.org.  I guess we can dream
>>>>> a bit.
>>>>> Jules - K2KGJ
>>>>> --
>>>>> TangerineSDR mailing list
>>>>> TangerineSDR at lists.tapr.org
>>>>> http://lists.tapr.org/mailman/listinfo/tangerinesdr_lists.tapr.org
>>>> --
>>>> ----
>>>> Phil Erickson
>>>> phil.erickson at gmail.com
>> --
>> ----
>> Phil Erickson
>> phil.erickson at gmail.com
>> --
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