Temperature sensing for room temperature SQUIDs - Page 2

Do you have a question? Post it now! No Registration Necessary

Translate This Thread From English to

Threaded View
Re: Temperature sensing for room temperature SQUIDs


Quoted text here. Click to load it
I

Tony Williams seems to have made it work; I though that he'd have to
provide separate in-phase and quadrature detection, but I was told
that he managed  to get away without it.

--
Bill Sloman, Nijmegen

Re: Temperature sensing for room temperature SQUIDs


Quoted text here. Click to load it

Thermistors are resistive.

Why do you think they are magnetic ?

Also, why does it matter ?

don

Re: Temperature sensing for room temperature SQUIDs



Quoted text here. Click to load it

Probably because they stick to a magnet. Lots of parts do.

Some parts are repelled by a magnet, which can be just as bad a
problem.

John


Re: Temperature sensing for room temperature SQUIDs


Quoted text here. Click to load it

I know they are magnetic.  I have measured several types  They are a
strange sort of metal oxide semiconductor thing.  Among the oxides are
magnetic ones

Quoted text here. Click to load it

It will cause a large error in the measured magnetic field.


Re: Temperature sensing for room temperature SQUIDs


On Sun, 13 Sep 2009 07:57:09 -0700 (PDT), MooseFET

Quoted text here. Click to load it

I trust you have evaluated superfield silicon hall effect sensors. You
mentioned a 1e9 field but neglected to mention the units.

Re: Temperature sensing for room temperature SQUIDs


Quoted text here. Click to load it

Kovar leads, for the glass bead type.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal
We've slightly trimmed the long signature. Click to see the full one.
Re: Temperature sensing for room temperature SQUIDs


Quoted text here. Click to load it

It is possible to vapor deposit non-ferric bi-metal plate and measure
the change in capacitance due to temperature.  If you are building a
chip anyway, you can build the sensor together with all the
electonics.

Quoted text here. Click to load it

AC is fine for capacitive plate.



Re: Temperature sensing for room temperature SQUIDs


Quoted text here. Click to load it

The electronics is all on the other end of a cable.  Perhaps I can
make a capacitor on the substrate of the sensor and sense it via the
cable.  This would be a driven shield.  The other though I just had
was to make a tuned circuit and measure the resonant frequency.

Where that coffee?



Re: Temperature sensing for room temperature SQUIDs


Quoted text here. Click to load it

One idea no one has mentioned yet, is to circulate a fluid into the
sensitive region, and temperature-measure it at a distance when it
flows out.

Ruby fluorescence has a decay time of about a millisecond, and
that's temperature dependent.  You can feed a ruby chip through
a fiber from a blinking blue or green LED, and look at the red
light that comes back for phase shift; phase-lock the blinking LED
so the red return light is (for instance) 50 degrees out of phase, and
the easily-measurable frequency is a thermometer.


Re: Temperature sensing for room temperature SQUIDs


Quoted text here. Click to load it

I like the idea that it uses two wildly different wavelengths.  This
means that I can have just one fiber that ends in the ruby and use a
filter to keep the strong pump LED out of the detector that picks up
the decay.  This would mean that the op-amps wouldn't crash into the
rails on the pump pulse.

Re: Temperature sensing for room temperature SQUIDs


Quoted text here. Click to load it

Platinum resistor, PN diode, there must be some thermocouple that is
non-magnetic.  I've used very fine copper-constatan TC.. it's only a
little magnetic.

George H.

Re: Temperature sensing for room temperature SQUIDs


Quoted text here. Click to load it

If you can through ordinary means see that it is magnetic, it must
be hugely so from my perspective.  A cute test requires some thread
and a strong magnet

Hang the object in question from about 4 feet of thread from a fixed
mounting point where there is no draft.

Bring the strong magnet to within 0.1 inches of one side of the object
and wait.

If the object moves at all it is more than tens times too magnetic.

Quoted text here. Click to load it


Re: Temperature sensing for room temperature SQUIDs



Quoted text here. Click to load it

I good magnet will attract the ink used on a dollar bill.

--
These are my opinions, not necessarily my employer's.  I hate spam.


Re: Temperature sensing for room temperature SQUIDs


On Sep 14, 7:44A0%pm, hal-use...@ip-64-139-1-69.sjc.megapath.net (Hal
Murray) wrote:
Quoted text here. Click to load it

Photocopies and things printed with Laser printers are magnetic.
So are:
Bird droppings
Dried blood
Most brass
Grey PVC sometimes
The hands of a machinist
Lamp black
Quaker Oats

Re: Temperature sensing for room temperature SQUIDs


Quoted text here. Click to load it

Yup, I think this is smaller than that.  I use it as a temperature
sensor in our optical pumping apparatus.  (Signal is extremely
sensitive to any temperature changes of the Rubidium cell.)  We get
sub 1 milli-gauss linewidths at fields of maybe 10 Gauss.  Any
magnetic stuff screws up the homogeneity and the linewidth.  I tested
it (years ago) by putting lots of thicker pieces of constantan near
the cell... line width was OK so a piece 10 times smaller was fine...
But it sounds like what you need is even more sensitive..... Still you
can get very thin wire.  It's an easy solution if it would work.

George H.

Site Timeline