ribbon mic:xvlk solution/DIY hall probe /plz elaborate

[ToobieSnack]

xvlk

here is american language slang interpretation for you :wink:

to mess with = to work with ..OR.. to experiment with

comes from "messing around" = "playing around"

can also be like "messing with" = disturb .. disect or construct or experiment ..

sorry for our stupid language .. hehe ... too flexible .. :sad:

so .. cj says if you still want to work (mess with) this idea of DIY hall probe to send him IM for more info ..
. CJ works (mess with) with these hall devices :grin:

edit:::: and now that i see this pic that cj posted he has many hall sensors and if you want to mess with (work with) them to PM him and he can help with parts ... thanks cj :thumb: mee too??????? :?

cj lots of people don't have the $300 for a measurement device and some are in countries where they can't be bought ...
xvlk idea to have reference magnets and recalibrate each time
for all the temp and other variable might be a good idea for small investment (nearly free if you have a scrap FDD)
recalibrate is only adjust one pot? (OR large variable resistor) and one small variable resistor / rough adjust and fine adjust .

and for ribbon mic we only need a very simple measurement ...

cj sounds like you have a lot of info AND
BTW great reference at the link you posted thanks .. :thumb:
can you add more input to this discussion ? :grin:

:idea: maybe in the future we can have something like:
the strip of paper on the side of a fish tank that changes color with different temperature OR
like similar device that is on batteries or battery package that changes color when touched to + and - :grin:
duracell had these for a while ..

OH AND DAMN CJ I JUST SAW THE PIC YOU POSTED !! :shock:

hook a dude up .. to a hall sensor or 2 ??? i think i got 75 cent in my bank .. hehe ; ... but those are 3 term ?

anyway

coll stuff to consider and discuss .. and help someone maybe too .. :grin:

later
ts

 

[CJ]

OK, alright. DIY cheapskate, you. Since your just doing a mag field, your circuit will be simpler than an rms type setup.

I would go dual op amp to split the gain.
0.001 across the hall sensor.
You can get away with common mode for a magnet I guess, so use a 3 lead hall chip.

Hall chips are set up to be run at a certain bias current. Usually 5 volts across the terminals puts them in their comfort zone. You can either put 5 volts ditrect, or go 24 volt supply thru dropping resistor(s).
I recomend the resistors for DIY 101, since the leads are close on the Hall chip (forgot that Hall was actualy a person). and so the resistor protects the pwr supply and the chip in case of a slip with a voltmeter probe.

Input to inverting pin of op amp thru a pot, which will be your cal adj.
Use another 0.001 across tyhe feedback resistor of the first op amp stage.

If going 3 pin Hall chip, hook the plus pin of opamp #1 into the wiper of a pot with resistors on both outer pins of the pot. One resistor to plus 5/24, the other to ground. 1 k trimmer will work.This is your zero offset/null adj.

Next, put another 0.001 cap on the output of op amp 1.

Feed output thru 10k resistor into inverting pin of next op amp. Ground non inverting pin thru a bias resisto. Value depends on chip type. Try 33 K.
Use another 0.001 cap on op amp 2 feedback resistor. Use another 0.001 cap on output. Feed output into 1k resistor then into your dc voltmeter and you good to go.

Paint side of hall chip with fingernail polish so you use the same side everytime. Don't ask me for fingernail polish. Try de-gaussing hall chip with tape head de-magnetizer everytime you measure. Inidium Arsenide might not soak up field, but leads sure will.




cj

 

[PRR]

I thought there were two kinds of "Hall Effect Chips":

1) Linear, very-very rare

2) Switching, used everywhere.

For a position sensor, like a floppy-drive track sensor or for detecting the position of the rotor in a brushless motor, I thought they used "switching" chips. The Hall effect sensor itself is linear, but needs amplification, and I thought the most common type was a "comparator". When less than 0.1T, output low; over 0.1T, output high. That's what most mechanisms really want to know.

I don't think Earth Magnetism is important for the kind of fields we need in speakers, microphones, motors. That's like saying Earth Gravity matters to a speaker. Yes, it does: mount a speaker face-forward like in a Hi-Fi, or face-up like in a car rear deck, the cone rest position will be different. But much-much-less than cone motion, or factory tolerances. Anyway: the same is true when you USE the mike. Point East, sensitivity is different than when you point West. Ever notice that? No, because the earth's field is much-much-much weaker than any practical electromagnetic motor/generator.

I don't think +/-20% error is a Big Deal. Changing a well-designed speaker from 5,000 Gauss to 10,000 Gauss gives another speaker, different, but still good. And when you are making ribbon mikes out of tinfoil and scrap-iron, you may not know what field-strength is "best". It is useful to know when field is very low, and useful to know if field is more-or-less when you change the magnet or the gap, but absolute accuracy is pointless. I think in Gauss, but I guess I am saying that +/-0.1T is plenty-good, and +/-0.3T is good-enough.

Hall Effect! Chips! Silicon!!!!! Bah!!!!!! Build an integrator. Put a wire in the gap. Reset the integrator. Pull the wire out of the gap. The integrator reading is proportional to field strength. You can calibrate it with the magnet gap from a blown speaker. Affordable speakers run 5,000 to 10,000 Gauss in the gap.

These days an integrator is an opamp and a cap, but you can also use a sensitive current meter with a very weak spring (no silicon-stuff at all).

 

[Marik]

[quote author="xvlk"]

It is good to have set of callibrated gaps (0.5 , 0.8, 1 , 1.2 ) and
before measurement check it.

[/quote]

If somebody wants such "reference" gaps, send me some magnetic assemblies of different magnet sizes for different strength and I will measure them for you. Actually, I think even single magnet measured at surface can be used as a reference.

 

[ToobieSnack]

wow ... yes marik i will do that. also if i sent you a ribbon like the one's i am using could you measure thickness for me and/or try it in one of your mics? :grin: PM with with address and info .. what size ribbon do you need?
thanks
ts

 

[bcarso]

I have an old Analog Dialogue featuring the use of Hall effect devices to do analog multiplication. Ouch!

As Dan Sheingold later quipped, "The Hall Effect is a small effect..."

 

[Guest]

[quote author="PRR"]Hall Effect! Chips! Silicon!!!!! Bah!!!!!! Build an integrator. Put a wire in the gap. Reset the integrator. Pull the wire out of the gap. The integrator reading is proportional to field strength. You can calibrate it with the magnet gap from a blown speaker. Affordable speakers run 5,000 to 10,000 Gauss in the gap. [/quote]

Yes, PRR, GOAL!!!!!! Rogowski potentiometer.
And with balistic galvanometer it is absolute ELECTRIC method
to measure (with wall and meter) magnetic field.

Yes, you not need nothing, Balistic Galvanometers are everywhere,
we have one on the wall at Secondary - school.
First: Determine ballistic constant.
Second: measure field with Rogowski method
Third: compute.

It is work for a week..... But absolut. I hate Sevres, ammeters and
all ****.
All I need is Weston normal pile,
Resistance normals
Galvanometer
and compensator.

Yes, good era of King Victoria, yes, my favourite time.


And by the way, much of Hall probes normally used are without amp.
That amp is in the LSI circuit. Really.

xvlk

 

[Guest]

[quote author="xvlk"]
Resistance normals
[/quote]
What this **** ???? Quantuum Hall generator.
We are living in time without prototypes. Meter is defined trough frequency
and resistor is defined also by some quanted.

And Weston pile ???? Josephson contacts !!!!!!!!!!


O.K. I am going to buy 2000 liters of liquid hydrogen.

And... Nobody made cryogenic superconductive galvanometter...
Good absolute toy for everyday using. Of course, in the vaacuum, because
Brown motion of air destroy everything

xvlk

 

[Marik]

[quote author="xvlk"][quote author="xvlk"]
Resistance normals
[/quote]
What this **** ???? Quantuum Hall generator.
We are living in time without prototypes. Meter is defined trough frequency
and resistor is defined also by some quanted.

And Weston pile ???? Josephson contacts !!!!!!!!!!


O.K. I am going to buy 2000 liters of liquid hydrogen.

And... Nobody made cryogenic superconductive galvanometter...
Good absolute toy for everyday using. Of course, in the vaacuum, because
Brown motion of air destroy everything

xvlk[/quote]


You got me here :green:

 

[PRR]

> Ballistic Galvanometers are everywhere

I have never seen one except in books. Sometimes it is not good to live in the USA, Land Of Progress. All the old ways are forgotten.

> Yes, good era of King Victoria, yes, my favourite time.

In english-speaking lands "Victoria" usually means Queen Victoria. She was around when Balistic Galvanometers were Advanced Technology.

I don't know "Rogowski". I have seen the technique called "snatch coil". To minimize ballistic/integrator error, you "snatch" the wire or coil out quickly, the same way a criminal would snatch a purse or jewelry.

Article: http://en.wikipedia.org/wiki/Rogowski_coil

http://www.eltekdataloggers.co.uk/sensors_energy_rc.shtml

 

[Gus]

would something like this work?

http://beale.best.vwh.net/measure/fluxgate/

 

[Guest]

[quote author="PRR"]
I have never seen one except in books. Sometimes it is not good to live in the USA, Land Of Progress. All the old ways are forgotten.
[/quote]
Whats that ??? Land of progress; What s going on, when all mathematics
we (electric peoples) use origins from 1893 Heaviside s book:
"Electromagnetic theory"
And nothing more advanced. I had read it. Nice .
If I have written paper on parametric systems (systems which is
not solvable via simple Operational calculus), every people on the
auditorium are shocked. Why ???? And I did only one small step.

[quote author="PRR"]
Queen Victoria.
[/quote]
Yes, that english, nounderstable language.
You have Mr. Brown ; Mrs. Brown,
but
King Jesus ; Queen Victoria.

Too irrational for my small head.

[quote author="PRR"]
I don't know "Rogowski".
[/quote]

Only measurement setup, somewhat like your coil.
If you snach one end of Rogowski coil, you can then also integrate.


Exactly this:
Article: http://en.wikipedia.org/wiki/Rogowski_coil

xvlk

 

[Guest]

[quote author="Gus"]would something like this work?

http://beale.best.vwh.net/measure/fluxgate/[/quote]

EXACTLY NOT. this is typical sensor for small flux (i.e.
geomagnetics, electro compass, etc) That permalloy (core)
is nonlinear. Muchmuchmore than every Hall probe (of course without
schmitt - trigger or nonlinear amp).

xvlk