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

Julius Madey hillfox at fairpoint.net
Sun Aug 2 13:49:02 EDT 2020


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 wrote:
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>     1. Re: Mag update? (David G. McGaw)
>     2. Re: Mag update? (David G. McGaw)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Fri, 31 Jul 2020 13:36:38 -0400
> From: "David G. McGaw" <david.g.mcgaw at dartmouth.edu>
> To: tangerinesdr at lists.tapr.org
> Subject: Re: [TangerineSDR] Mag update?
> Message-ID: <3718db2a-97b4-eba5-8f0a-e94ead711cd7 at dartmouth.edu>
> Content-Type: text/plain; charset="utf-8"; Format="flowed"
>
> 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>> 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>
>>>      	*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/
>>>      <https://nam12.safelinks.protection.outlook.com/?url=https:%2F%2Fweb.njit.edu%2F~hmkim%2F&data=02%7C01%7CDavid.G.McGaw%40dartmouth.edu%7C2e59f624469544810c1c08d8356521e1%7C995b093648d640e5a31ebf689ec9446f%7C0%7C0%7C637318055785499423&sdata=Nz%2B0y9A0svN6RegTKpvfpWgJ%2FCb1N1vKkFr71fqtDFg%3D&reserved=0>
>>>      104 Tiernan Hall, 161 Warren Street, Newark, NJ 07102
>>>
>>
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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>
> To: tangerinesdr at lists.tapr.org
> Subject: Re: [TangerineSDR] Mag update?
> Message-ID: <f86f2596-ef2b-25c7-5b12-3f83c4429cb3 at dartmouth.edu>
> Content-Type: text/plain; charset="utf-8"; Format="flowed"
>
> 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.
>>
>>
>> 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>> 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%7C4a7b93ba3ecd455d4e0f08d83568b144%7C995b093648d640e5a31ebf689ec9446f%7C0%7C0%7C637318071068004568&sdata=O09d%2FBt6N3Iq%2FUVQ5KdQz6V0Km3YIN%2BucnCkc1JQC8E%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>?? (973)?596-5704
>>>      https://web.njit.edu/~hmkim/
>>>      <https://nam12.safelinks.protection.outlook.com/?url=https:%2F%2Fweb.njit.edu%2F~hmkim%2F&data=02%7C01%7CDavid.G.McGaw%40dartmouth.edu%7C4a7b93ba3ecd455d4e0f08d83568b144%7C995b093648d640e5a31ebf689ec9446f%7C0%7C0%7C637318071068004568&sdata=W4LqWL2HfX4hkY0cMhqWDsY%2FlWS9nz1bpjcEZ9%2FbSNE%3D&reserved=0>
>>>      104 Tiernan Hall, 161 Warren Street, Newark, NJ 07102
>>>
>>
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