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The uCurrent, which I have and like, makes a big deal that it gets its accuracy because it has a tiny burden voltage, much smaller than the 0.3V you list.  As I understand it that's relevant to the uCurrent because of the external meter.  Does your solution make it irrelevant because you're measuring inside your own system?

 

I'm a software guy, and bare boards or even kits that require me to do SMD work aren't useful to me.  I happily paid $60 for the uCurrent, and would pay at least that much for your board if it came calibrated and ready-to-use.  It'd be nice if there was a service that sold complete and tested boards for this and other neat stuff 430 folks are designing.

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43oh Store link   I found myself wanting a dedicated power monitor to use while developing battery-powered application circuits, so I built one using the MSP430G2402.    http://code.google.com/p/powe

The situations where I want to measure current are usually below 10uA, and sometimes below 1uA.  I'd like at least one, preferably two, significant digits in the result.   As for the cost, $7 more f

Hi   I just made a little blog entry about this great and useful tool.   http://rubines.blogspot.co.at/2013/07/meet-powerscope.html     Cheers Rubi

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The uCurrent, which I have and like, makes a big deal that it gets its accuracy because it has a tiny burden voltage, much smaller than the 0.3V you list.  As I understand it that's relevant to the uCurrent because of the external meter.  Does your solution make it irrelevant because you're measuring inside your own system?

 

I'm a software guy, and bare boards or even kits that require me to do SMD work aren't useful to me.  I happily paid $60 for the uCurrent, and would pay at least that much for your board if it came calibrated and ready-to-use.  It'd be nice if there was a service that sold complete and tested boards for this and other neat stuff 430 folks are designing.

 

Hi Pabigot... I approached mechG to getting this done for the Store.. However to get it priced to hobbyist levels is a bit difficult. The only thing that is troublesome is the $11 LCD.. Do you or anyone have a cheaper alternative?

If I can get a reasonable one, I'm ready to assemble it.

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Hi Pabigot... I approached mechG to getting this done for the Store.. However to get it priced to hobbyist levels is a bit difficult. The only thing that is troublesome is the $11 LCD.. Do you or anyone have a cheaper alternative?

If I can get a reasonable one, I'm ready to assemble it.

 

you really want to be down in the 2-4 dollar area for the lcd. 

they have a blue version for the same price NHD-C0216CZ-NSW-BBW-3V3

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The current LCD is a character LCD but a number LCD would do the job just fine. You'd have to add some labels outside the display (since you cannot display the mW in a number display).

 

 

you really want to be down in the 2-4 dollar area for the lcd. 

they have a blue version for the same price NHD-C0216CZ-NSW-BBW-3V3

Thanks all... I'll just do the PCBs for now. We can still pursue the LCD cost till  then.. Also, I'd like the designer(mechG) to be happy with what we choose, since it's his design.

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The uCurrent, which I have and like, makes a big deal that it gets its accuracy because it has a tiny burden voltage, much smaller than the 0.3V you list.  As I understand it that's relevant to the uCurrent because of the external meter.  Does your solution make it irrelevant because you're measuring inside your own system?

......

 

Burden voltage is always relevant if the drop impacts how your circuit draws current.   When I was developing the PowerScope, I tried using smaller shunt resistors of .1ohm and 100 ohms to reduce the burden voltage to .03v max.  Unfortunately, the tiny voltages were swamped by the contact resistance of my solderless breadboard connections.   So I stuck with the 1 ohm and 1000 ohm shunts for the moment and lived with the .3v max burden.

 

Now that I have it all on PCB,  I intend to try lowering the shunt values again to see if it can handle it.  The tiny voltages across the shunts might still be affected by capacitive effects since the PowerScope is not shielded like multimeter enclosure usually are.

 

Keep in mind that you will only see the maximum burden voltage at maximum rated current, which is 300mA in the high range and 300uA in the low range.   Actual burden voltage is 1mV/uA (one milliVolt per microAmp) in the low range and 1mV/mA (one milliVolt per milliAmp) in the high range.

 

A project I am working on right now draws about 3mA, so the total burden voltage is 3mv on the high range of the PowerScope.

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I think the cost expectation is set by the fact that decent multimeters can be had for $25 these days.   Most of them cannot measure in the sub-microAmp range, though.

 

 

......  I happily paid $60 for the uCurrent, and would pay at least that much for your board if it came calibrated and ready-to-use.  ...

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The situations where I want to measure current are usually below 10uA, and sometimes below 1uA.  I'd like at least one, preferably two, significant digits in the result.

 

As for the cost, $7 more for one LCD over another would not influence my purchase, but then I'm not approaching this as a hobbyist--though I suppose from the EE perspective I'm that at best.  With the current maker revolution, the lines between hobbyist and professional are getting blurred.  When Ladyada says a $60 uCurrent gets within the ballpark of a $15K Agilent ammeter, and a $20 DVB-T does as well as a $1500 Ettus USRP for gross RF spectrum analysis between 100MHz and 2GHz, even "talented amateurs" can pretend to be professionals.

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@Bluehash - Have you considered using the dirt cheap Nokia displays that some have used over at DP (including at least a couple of projects using a 430). They can be had for $1.09 and are graphics displays and can be used for plain text.

http://dangerousprototypes.com/forum/viewtopic.php?f=19&t=3486
 

 

@Pabigot - I would be happy to solder it all up for youand test it, if you would be willing to send me the bits for 2 and I keep one and send you a constructed one.

 

edit - added link

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@Bluehash - Have you considered using the dirt cheap Nokia displays that some have used over at DP (including at least a couple of projects using a 430). They can be had for $1.09 and are graphics displays and can be used for plain text.

http://dangerousprototypes.com/forum/viewtopic.php?f=19&t=3486

 

 

@Pabigot - I would be happy to solder it all up for youand test it, if you would be willing to send me the bits for 2 and I keep one and send you a constructed one.

 

edit - added link

Thanks.. that's a good find.. I'll let mechG chime in. Does it have a backlight?

Also, first batch of powerscope PCBs are being fabbed. 

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Yes it has a backlight (LED) and if you read through the posts you'll find links to some code the guys have used on 430's, so I'm sure it would be simple for you guys to get something running with it. Also a few suppliers noted there. Note that the Ebay suppliers charge about $3 or $4 for these, but Mats found another supplier that sold him 20 for $1.09 each (listed in one of the latter posts). I got one of these about a year ago, but haven't got to using it yet unfortunately. You can fit a lot of information and / or pictures on them (as shown in some of the posts) and they're a good little unit that is hard to go past for the price.

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