Gaussmeter Kit Group-Buy

[spy]

Voila, my GaussMeter!


I'm not very happy with the enclosure but it could be worst!

[RedHouse]

Voila, my GaussMeter!


I'm not very happy with the box but it could be worst!

Looks good to me!

[defaced]

I'm digging this. I just finished building the one I got for my work and checked out some forged steel. Interestingly enough, when whole (this is a cylinder shape), it's not magnetic, but if you cut out a wedge, the ends are magnetic. So it looks like the field is concentric with the part and not radiated outward. I've yet to fully understand the implications of this, but since we keep blowing holes through parts unintentionally (TIG welds), knowing if the magnetic field of the part is assisting in the problem is a good thing to run up the flag pole.

[automan]

Maybe the trama occuring during the act of cutting it temporarily magnetises it. Kinda like how you can take an iron rod and slam it into a fire hydrant and use it to pick up keys out of a drainage grate. (thank you MacGyver)

[David Schwab]

If you align any piece of mild steel North-South and whack it with a hammer, it will become magnetized.

[defaced]

Similarly, if you align any piece of steel north/south and let it sit there, it will become magnetized. This is an issue with long term storage of pipe lengths because welding on magnetized steel is a nightmare. Google

I'll check out some other saw cut steel in the shop and see what I get. Forged steel is known to be magnetic, there are even people out there who specialize in degaussing the stuff: Magnetic Products and Services, Inc. (The Gaussbusters) - Home Page

[LtKojak]

If you align any piece of mild steel North-South and whack it with a hammer, it will become magnetized.

Is this what Possum does to magnetize his PAFs...?

[belwar]

Is this what Possum does to magnetize his PAFs...?

hehehe!

[defaced]

Alrighty, after some more work, I've got some context to what I'm playing with. Bad things start to happen to arcs above 60 gauss. Now I know Brad (RedHouse) calibrated these, but am I playing in a range where the error of the calibration could be effecting my readings significantly? If they're off by 5 gauss, that's no problem, off by 10, that's starting to make me nervous, off by 20 and I need to find a way to calibrate this beast.

Sawing these parts doesn't seem to be inducing magnetism. Machining might, but I'll have to wait until my big part gets back from the machine shop to see.

[-Elepro-]

A1302 sensor is not rigth for accurate measuring in that range.... least of all brad calibration....

you need a high sensitivity, factory calibrated sensor...

[defaced]

Could you suggest a sensor that would be accurate in that range and compatible with the PIC firmware?

[-Elepro-]

A1321LUA Calibrated Linear Hall-Effect Sensor

with this range would be about +- 450 gauss.... and it is factory calibrated

[defaced]

Excellent. So since this is calibrated from the factory, I just enter 5.000mv/G, which is the data sheet value, into the calibration for the PIC and I'm good to go?

[-Elepro-]

i think they send a datasheet for your specific sensor.... with the exact sesitivity value... (it will be 5.000 or 5.010 or 5.026.... ecc)

(it is not a special sensor... only it is a sensor measured before sell)

yes... enter value in calibration menu and you are good

[-Elepro-]

today i tested the ad22151....
as i supposed, for this application it doesn't need any external component (only the decoupling cap like the a1302).... it work very well and i have same value with both sensor....

but unfortunately the pole shown on display with ad22151 is reversed....
i'm sorry for this but as you can see there is an error in datasheets

POSITIVE B FIELD INTO TOP OF PACKAGE RESULTS IN A POSITIVE VOLTAGE RESPONSE

The presence of a south-polarity (+B) magnetic
field, perpendicular to the branded face of the device package,
increases the output voltage VOUT.....

so:

you can send me your PIC and i'll replace firmware with 2.2 version (where it is possible to store polarity operation for both sensor.... ) and i will return it (with not insured and not trackable economic air mail) for free....

or

you can wait and will have a discount for version 3 (new professional PCB with double side layer, double side soldermask and silkscreen + a small PCB for double side A1302/AD22151 probe.... + upgrades in firmware ..... average mode (read this ) + on board 4 tactile push button with power on/off-backlight on/off- sensor change - and all other functions... and on board usb connector for probe.... super easy to mount... only battery wire.... prototype picture soon...

bye