Nothing interesting in it except for the whole "Average Joe can't test that crazy Aussie bloke's claims of accuracy"-part.
Oh NO! Go for Gold Dave. If you try to match the red to the soldermask red your head will explode.
Kickstarter is refusing to accept my US credit/debit card, even after calling my bank and having them "open the card" for overseas payments through the funding period. Is anyone else having this problem?? Am I going to have to live with just my plain old non-gold uCurrent?!?!
Kickstarter is refusing to accept my US credit/debit card, even after calling my bank and having them "open the card" for overseas payments through the funding period. Is anyone else having this problem?? Am I going to have to live with just my plain old non-gold uCurrent?!?!JS filter (Noscript)?
I had to allow a sh**load of JS sites for the CC# verification step...
Kickstarter is refusing to accept my US credit/debit card, even after calling my bank and having them "open the card" for overseas payments through the funding period. Is anyone else having this problem?? Am I going to have to live with just my plain old non-gold uCurrent?!?!JS filter (Noscript)?
I had to allow a sh**load of JS sites for the CC# verification step...No, I'm not blocking anything, I've tried on Chrome and Firefox. it seems to make it through trying to authorize because it tells me that it's declined (and yes, the card does work elsewhere)
In short: I'd love to see a nice, small, affordable precision preamp-board be spun - considering your outreach into the community the volume should be enough to bring down the initial costs to affordable levels... and by adding some general filtering capabilities such a product would surely simplify many hobbyists and engineers lifes ... µVoltage µPreAmp µFilter µAmp µBBB (bread board breakout)..
How much current does the µCurrent Gold take from it's coin-cell while running?
I've got a few CR123A 3V Li batteries here... like used in modern LED flashlights... 1600 mAh + ... is there enough room in the case to fit one of those there? (That would easily give some 14 days of continuous use and even be cheaper on the money/mAh scale)
-snip-...µVoltage µPreAmp µFilter µAmp µBBB (bread board breakout)..I do have these in mind.
QuoteCR123A 3VNot sure, don't have one to hand to test it.
Kickstarter is refusing to accept my US credit/debit card
did you already publish the schematic and BOM of the new design somewhere?
Your article for the old version led to some confusion also on the German heise online site (Heise also publishes the - here - famous c't magazine).
The worse specification from the old article is assumed valid for the new design also.
Publishing the correct / updated informations would perhaps clarify everything.
PS: Just found out, that you were using a CSM2512 metal foil precision shunt, from Vishay Precision. (about 6AU$ @ 1000EA)
Wow, that's really a big improvement over the old design. Quite sophisticated.
But I'm still curious, which ChopAmp you've used, or which circuitry, to achieve that 300kHz BW @ gain = 100...
Must be a 30MHz UGBW type.
Alternatively, if the aim is to protect an expensive/hard to get precision shunt resistor, maybe add a small sacrificial low-value 1206/0805 resistor to protect it - cheaper than a fuse, and easy enough to replace.
I was going to suggest (if it isn't too late for a board rev) having optional mounting pads for SMD fuse holders like Mike suggested (e.g. Littelfuse NANO2).
Would be great upgrade that people could do by cutting a couple of (otherwise fusible) traces and mounting these between R1 & SWA-1A, and between R1 & R9.
BTW, is R9 connected to the correct terminal of R1? Isn't that putting the uA range through the Kelvin sense terminal?
What is the purpose of the Short position while switched on ?
Would it not make more sense to have the short in place when in "off" mode (as well)?
Might putting a cap across R7 make it a little less sensitive to noise in the virtual ground ?
For R1 the connection of R9 makes no difference, because R9 is 1000 times bigger than R1, and the current 1000 times smaller.
R9 should have been connected to IN- directly, but the chosen circuitry is easier concerning the switch and more precise.
Normally, R1+R9 = 10.01 Ohm gives an additional 0.1% error for the µA (10.00 Ohm) shunt, but Dave implied a trick:
R2 is in parallel to the 10.01Ohm, thereby reducing the µA shunt again to exactly 10.00Ohm.
2) R1 does not need a fuse, normally. It is rated for nominal 10A (1W) , 31A max, see Vishay specification.
But I estimate, it will desolder itself when > 500mW / > 7A are applied.
Correct.
For switching limitation reasons R2 is always connected, so gives an error of 9.99 miliohms lower than nominal R9 value of 10R on the uA range. But we conveniently have R1 which is 10 miliohms - close enough!, so we put R9 and R1 in series which is then parallel with 10K R2 to give us back our precise 10R uA shunt. And this is done via the sense line, which at uA level makes no difference, but that enables another trick at the same time:
In mA mode, R9 is now switched in series with the sense line and opamp, through which no current flows, so no effect.
I was rather chuffed when I came up with this solution
did you already publish the schematic and BOM of the new design somewhere?
The info is on my project page:
http://www.eevblog.com/projects/ucurrent/