[TangerineSDR] TangerineSDR Digest, Vol 16, Issue 32_RM3100temperature effects

Mon Aug 3 12:15:19 EDT 2020

This all sounds very good. I’m eager to see the results.

73 de Nathaniel W2NAF

From: TangerineSDR <tangerinesdr-bounces at lists.tapr.org> On Behalf Of Julius Madey via TangerineSDR
Sent: Monday, August 3, 2020 11:57 AM
To: Kim, Hyomin <hmkim at njit.edu>; TAPR TangerineSDR Modular Software Defined Radio <tangerinesdr at lists.tapr.org>
Cc: Julius Madey <hillfox at fairpoint.net>
Subject: Re: [TangerineSDR] TangerineSDR Digest, Vol 16, Issue 32_RM3100temperature effects

Great !   Out of direct sunlight and close to ground level would be best.
On 8/3/2020 11:28 AM, Kim, Hyomin wrote:
This time, I will try to place the sensor as close as possible to the science magnetometer at Jenny Jump and insulate it to minimize the temperature effect if any.
Gil (the site manager) and I will not be available until next week but will try to address this issue as soon as possible.

Hyomin

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

On Sun, Aug 2, 2020 at 1:49 PM Julius Madey via TangerineSDR <tangerinesdr at lists.tapr.org<mailto:tangerinesdr at lists.tapr.org>> wrote:
That is the claim.  So either that's not the case, or perhaps it holds for levels in excess of a few hundred nT or something else is causing the variations that were observed at Jenny Jump and in my various tests.  It is probably not B fields very local to the adapter board, which sees currents in the 10mA range.  Just did some tests with 100mA into a twisted pair of #31 magnet wire held near different parts of the RM3100 board.

If the twisted pair was 0.5cm or more away from anything on the board, no effect observed.  If it lay directly on one of the sensing inductors, effect was ~ 50nT.

Another thought on temperature stability .... place the mag in an in-ground vault.  Back in the 60's when we needed xtal oscillator stability on the cheap and better than the usual xtal oven of the day, we put the oscillator assembly about 3 feet underground.  Very stable short term and excellent long term.  It would certainly work for 24 hour observation periods.

Jules Madey-K2KGJ
On 7/31/2020 1:38 PM, tangerinesdr-request at lists.tapr.org<mailto:tangerinesdr-request at lists.tapr.org> wrote:

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Today's Topics:

   1. Re: Mag update? (David G. McGaw)

   2. Re: Mag update? (David G. McGaw)

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Message: 1

Date: Fri, 31 Jul 2020 13:36:38 -0400

From: "David G. McGaw" <david.g.mcgaw at dartmouth.edu><mailto:david.g.mcgaw at dartmouth.edu>

To: tangerinesdr at lists.tapr.org<mailto:tangerinesdr at lists.tapr.org>

Subject: Re: [TangerineSDR] Mag update?

Message-ID: <3718db2a-97b4-eba5-8f0a-e94ead711cd7 at dartmouth.edu><mailto:3718db2a-97b4-eba5-8f0a-e94ead711cd7 at dartmouth.edu>

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Interesting, this, as it says on the RM3100 webpage "Measurements are

stable over temperature and inherently free of offset drift" and a

temperature coefficient is not even mentioned in the specs.

David N1HAC

On 7/31/20 11:18 AM, Julius Madey via TangerineSDR wrote:

Good morning all.? Betty Zhang at PNI is responding to the request and

has asked for more information which I have supplied, including some

of the JJ test comparisons, how I ran the calibration runs I did, data

reduction, etc.

I would suggest one further item for consideration in getting to a

useable solution.? If RM3100 temperature turns out to be a concern,

place the sensor in a small foam insulated box with a proportionally

controlled heater which maintains the temperature at something just

above what would be considered the highest environmental temperature

around the sensor.? That should be relatively simple to do without

introducing an interfering magnetic field local to the sensor.? Some

power would be required but with careful design, I would think well

within 1 watt.

Another possibility would be using peltier effect heat pumps to do the

same thing, although the technology would probably result is stronger

local B fields from the peltier device and require more power.? The

insulated foam box and proportional heater is also probably the

cheapest approach considering the need to keep overall costs for the

expected users low.

Regards,

Jules

On 7/31/2020 10:26 AM, David Witten wrote:

Hyomin,

I'm not certain what the next step should be.? Julius is hoping for

further response from PNI on this subject.

If temperature compensation does account for the differences in

observed response I would think that the important thing to? do may

be to find a way to calibrate out the discrepancy.? Then we can look

at insulation to further minimize the effect.

Calibration will hopefully give us more meaningful values to begin?with.

Insulation will dampen the effect of those behaviors over short

timespans.

Fortunately, neither requires changes?in the basic circuit, just

adjustments to the data collection and device packaging.

Dave

On Fri, Jul 31, 2020 at 9:10 AM Kim, Hyomin <hmkim at njit.edu<mailto:hmkim at njit.edu>

<mailto:hmkim at njit.edu><mailto:hmkim at njit.edu>> wrote:

    Hi Dave

    Sorry that I've been out of the loop for a while as I was

    completely caught up with something else. May I ask you what the

    current status is?

    I can visit Jenny Jump if there is something that I can do. At

    this moment, I cannot think of anything that can be fixed from my

    end.

    If the temperature compensation is the issue, I could install

    insulations around the sensor.

    Hyomin

    NJIT logo

    <https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.njit.edu%2F&data=02%7C01%7CDavid.G.McGaw%40dartmouth.edu%7C2e59f624469544810c1c08d8356521e1%7C995b093648d640e5a31ebf689ec9446f%7C0%7C0%7C637318055785489421&sdata=TmqWJw6VYdRSrTgS2xSIifG4OTUj6z5lcBLqd2UedyY%3D&reserved=0><https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.njit.edu%2F&data=02%7C01%7CDavid.G.McGaw%40dartmouth.edu%7C2e59f624469544810c1c08d8356521e1%7C995b093648d640e5a31ebf689ec9446f%7C0%7C0%7C637318055785489421&sdata=TmqWJw6VYdRSrTgS2xSIifG4OTUj6z5lcBLqd2UedyY%3D&reserved=0>

      *Hyomin Kim*

    Assistant Professor

    Physics

    Center for Solar-Terrestrial Research

    Institute for Space Weather Sciences

    hmkim at njit.edu<mailto:hmkim at njit.edu> <mailto:hmkim at njit.edu><mailto:hmkim at njit.edu>?? (973)?596-5704

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Message: 2

Date: Fri, 31 Jul 2020 13:37:51 -0400

From: "David G. McGaw" <david.g.mcgaw at dartmouth.edu><mailto:david.g.mcgaw at dartmouth.edu>

To: tangerinesdr at lists.tapr.org<mailto:tangerinesdr at lists.tapr.org>

Subject: Re: [TangerineSDR] Mag update?

Message-ID: <f86f2596-ef2b-25c7-5b12-3f83c4429cb3 at dartmouth.edu><mailto:f86f2596-ef2b-25c7-5b12-3f83c4429cb3 at dartmouth.edu>

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Interesting, this, as it says on the RM3100 webpage "Measurements are

stable over temperature and inherently free of offset drift" and a

temperature coefficient is not even mentioned in the specs.

David N1HAC

On 7/31/20 11:44 AM, Julius Madey via TangerineSDR wrote:

One more thought.? I've asked PNI for information both on temperature

and supply voltage sensitivity, the only two variables I could think

of besides the need to minimize local B fields due to currents in

circuit board traces, nearby wiring, etc.

I did not find data on the temperature stability of the 3.3 volt

regulator Dave's JJ board? is using but the regulator I used with the

original adapter board Dave sent me has about 5 millivolts of change

out of 3.3 volts between 25 and 50 C and Dave's is probably similar.?

That doesn't seem like enough change to produce the observed

variations but that information was given to PNI as well.