[TangerineSDR] Fwd: temperature tests

[David Witten]

---------- Forwarded message ---------
From: David Witten <wittend at wwrinc.com>
Date: Thu, Aug 6, 2020 at 12:19 PM
Subject: Re: temperature tests
To: Julius Madey <hillfox at fairpoint.net>


Jules,

I'm not certain that really specific parameters have been stipulated.  The
goal always seems to be "can useful science be done with this" and "is this
the best we can afford".  Neither goal has been entirely expressed in
numbers.
But I do not see any real competitors on the horizon.

It is really a matter of squeezing all the performance  out of what we have.

Dave

On Thu, Aug 6, 2020 at 12:07 PM Julius Madey <hillfox at fairpoint.net> wrote:

> Pink Flamingos are popular in some areas !    Garden gnome sounds like a
> more 'blend into the landscape' item though !
>
> Something like aluminized mylar somewhere towards the outer shell of the
> enclosure could help as a reflective barrier.
>
> I'm really curious to see how the vertical PVC pipe in soil works out.
>
> If absolute accuracy of the mag measurements isn't needed and an ~1degree
> temperature change can be achieved over most of a 24 hour period, that
> might be all that's necessary; do we know what Hyomin's goal on
> measurements is?
>
>
>
> On 8/6/2020 12:46 PM, David Witten wrote:
>
> Julius,
>
> Thanks for sharing that.
>
> My plan for putting a device outside for testing looks very similar.
>
> I am planning to place the device in a piece of PVC pipe nestled inside
> that amount of Pink foam.  I have some stuff that set designers and outdoor
> sculptors use to seal the Foam material to waterproof it and make it hard.
> Then almost any other paint/sealant can be applied.  It can be buried or
> left out in the weather.  I also thought about wrapping it in Tyvec.
>
> The fact that I can make this stuff look like almost anything (garden
> gnome?) should help with my neighborhood's covenants.
>
> Dave
>
>
>
> On Thu, Aug 6, 2020 at 10:54 AM Julius Madey <hillfox at fairpoint.net>
> wrote:
>
>> Dave,
>> I've had a lot of experience with calibrating thermal sensors,
>> thermoelectric heat pump temperature chambers, etc.  This was a 'quick and
>> dirty' test with a small, essentially zero gradient temp chamber.
>>
>> Aluminum is about second to copper in heat conductivity.  A small 100 ohm
>> wirewound resistor is a snug fit in a hole bored through the aluminum block
>> and filled with heat sink compound in the photo.  With the insulation
>> provided by the block of foam, the aluminum block is an isothermal source
>> in close contact with the assembly consisting of your original small board
>> and the plug in RM3100 module above it.
>>
>> Placed in the cavity in the foam block and with relatively slow
>> temperature change, the cavity volume is for all practical purposes, zero
>> gradient.
>>
>> 50 to 75mA of current  (0.25 to 0.56 watts) into the resistor produced up
>> to 35-40 degrees above ambient within the chamber with rise times slow
>> enough to maintain effectively zero temperature gradient within the
>> heater/board assembly.
>>
>> I guess +/- 0.5 to 1% per degree C tempco for a wide range inexpensive 3
>> axis magnetometer isn't too bad for general applications if in fact the
>> data we're seeing so far is real and not an artifact due to some unknown.
>> But is it adequate for the requirements of the HAMSCI project ?
>>
>> And, if temperature control of some sort is required, what's the least
>> expensive, most practical way to achieve that?
>>
>> Regards,
>> Jules
>>
>>
>>
>>
>> On 8/6/2020 10:12 AM, David Witten wrote:
>>
>> Jules,
>>
>> Very interesting.  How are tiy doing the heating?  Conventional oven?
>>
>> Dave
>>
>> On Thu, Aug 6, 2020 at 12:07 AM Julius Madey <hillfox at fairpoint.net>
>> wrote:
>>
>>> Dave,
>>> I made up a small insulated temperature chamber from a 5 x 5 inch block
>>> of insulating foam board then bored a 1.5 inch diameter hole to the
>>> center.  Heater is a small block of aluminum with a 100 ohm resistor  in a
>>> drilled hole in the block filled with heat sink compound and connected to a
>>> twisted pair leading out of the chamber, resulting in a small area loop
>>> which creates a small but constant local B field as noted in the attached
>>> plots.  Heater current typically 55mA for the temperature spans noted.
>>>
>>> The RM3100 is mounted on your original small test board which is glued
>>> to the Al block and with 18 inch i2c bus leads running to a SparkFun
>>> differential i2c board that supplies the 3.3 volts to the RM3100.  Inner
>>> chamber is closed off with a foam plug of the same material.
>>>
>>> Both the sense and the magnitude of the tempco for the two RM3100s I
>>> have is different.  One is positive, the other negative.  Z axis was the
>>> hardest to evaluate probably due to the relatively small magnitude changes
>>> and the likely larger variation of the vertical field component during the
>>> tests.
>>>
>>> A better characterization would require a lab grade setting with
>>> mu-metal chamber, precision 3 axis Helmholtz coils and precision
>>> temperature chamber.
>>>
>>> Assembling the simple in-ground unit I mentioned in my last and will
>>> hopefully try this weekend.
>>>
>>> Haven't heard back from PNI yet.
>>>
>>> Regards,
>>> Jules
>>>
>>>
>>>
>>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.tapr.org/pipermail/tangerinesdr_lists.tapr.org/attachments/20200806/f5b5a6a7/attachment-0001.html>