DC background subtraction

On a sunny day (Tue, 8 Jan 2019 20:27:05 +0000) it happened piglet wrote in :

I remember a story in one university where I was where they have su[p]per conducting magnets to test some materials. Guy comes in a with a metal cart carrying some equipment, it gets pulled towards the supper magnet, and BANG, helium (IIRC) boiling disaster...

So that makes me wonder if you can just use a sensor _outside_ the cold magnet and if that would work just as well.

The gain is all noninverting. At the output, both signal and offset get multiplied by positive numbers. The numbers are different, is all.

There's no difference whatsoever between this and a normal split supply noninverting stage except that a different node is labelled 'ground'.

If the orig DC The Final Frontier

Cheers

Phil Hobbs

Right. that's a big low temperature super conductor magnet. (I use the have new students grab onto a screw driver and approach the dewar/ magnet slowly. The force goes as the sixth power of the distance and so grows very rapidly.)

In this case it will be a small field ~ 1" diameter toroid.

George H.

Right... my comment was a little tongue in cheek.. I should have added the smiley face.

Yeah it's a little hard to measure the lower frequencies of 1/f noise, things below 1 Hz.

George H.

Not hard, just tedious. Data loggers make it easier, but you do have to accumulate data for minutes or longer.

ce amp,

like this. And they produce downloadable acquisition files for USB. Probab ly something available at HomeDepot :-)

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s 12-bit resolution on differential analog input (multiple channels), and h as analog output channels which can provide a programmable reference for th e differential conversion. Sample rate max's out at 50ksps and can be strea med into the laptop via USB. It does a bunch of other stuff too, looks like a good catch-all gadget for the lab. Input range seems a bit limited for t his application, but he should be able to figure something out. No waste of bits here.

There may be only 4 bits left for the residual but the ultimate resolution of the original input signal is [about] 50 ppm, which is pretty darn good. The reason is because of fairly precision offset reference and the conversi on of the differential input make this a subranging A/D [without the auto-r anging part]. If he uses an IA with gain x20 to drive the LabJack inut, he gets 2.5 ppm etc. Not sure of the physics involved or the computational cha racterization of the phenomenon they're looking at, but that sounds like pr etty good resolution. This looks like something that would come in handy on occasion, and it's ch eap.

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ence amp,

ls like this. And they produce downloadable acquisition files for USB. Prob ably something available at HomeDepot :-)

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s 12-bit resolution on differential analog input (multiple channels), and h as analog output channels which can provide a programmable reference for th e differential conversion. Sample rate max's out at 50ksps and can be strea med into the laptop via USB. It does a bunch of other stuff too, looks like a good catch-all gadget for the lab. Input range seems a bit limited for t his application, but he should be able to figure something out. No waste of bits here.

Looks look like one of those tools that pays for itself a couple of times o ver the first time you use it, saving on all that proto labor.