Electronics > Beginners

Damn killed uCurrent first time out. Lol

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veryevil:
Hey, I just got my first two uCurrents and first time out I think I killed one! Switched it to nA range while drawing about 9uA. Now the voltage output is all screwy (technical term).

What do I need to replace to get it working again? Just the  MAX4239? Will I have damaged anything else?

Is there any over voltage protection that could be placed on the input of the MAX4239?

FenderBender:
I don't think there's much proteciton on it because it will screw with the burden voltage which needs to stay low.

But perhaps something can be done.

JoannaK:
I assume that the diagram at the http://alternatezone.com/electronics/ucurrent/uCurrentArticle.pdf is valid.

As far as I'm willing to guess, the Max4239ASA+ has blown.  Good news is that it's merely couple USD and SO-8 pin out should be user replaceable, if one has any experience of surface mount rework.

For the future, adding couple protection diodes (from max4239 pin 3 to supply rails) could perhaps prevent similar mistakes. And as far as I understand those should not affect the normal measurement.

Anyone willing to test on their uCurrent ?

tld:
 :palm:
--- Quote from: veryevil on January 09, 2013, 03:27:26 pm ---Hey, I just got my first two uCurrents and first time out I think I killed one! Switched it to nA range while drawing about 9uA. Now the voltage output is all screwy (technical term).

What do I need to replace to get it working again? Just the  MAX4239? Will I have damaged anything else?
--- End quote ---

Why would switching it to nA-range kill it?

All you're doing is switching from 10kOhm + 10 Ohm to just the 10kOhm sense resistor.

That'd make the voltage output all screwy, but only until you change it back to uA range, it shouldn't kill anything?

(disclaimer: I haven't had enough coffee to do a decent impersonation of awake yet... )

veryevil:

--- Quote from: tld on January 10, 2013, 08:17:05 am ---
Why would switching it to nA-range kill it?


--- End quote ---

My guess is that 8uA is 8000nA which is 8 times higher than the 1000nA input range and also is trying to set 8v output.

I have no problem with replacing the chips SMD on this scale is easy. Its just which bits, pretty sure just the MAX chip.

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