Overcoming Burden Voltage

[PiMaker]

Hello,

I think I have a problem with my meter's burden voltage.  I have to log current ranging from 1mA-3A but my circuit seems like it is being starved for voltage (works fine without the meter).  If I put a voltage regulator on the output of the meter to ensure I get the voltage I need, then use that voltage to drive the circuit, will that work?  Do you see any issues in doing that?  I guess the better question is, is there a better solution?  I've tried to find a meter that has a low enough burden voltage but couldn't find anything for that range. 

Voltage range is 3.3-4.2V.  Datasheet for the meter says burden voltage for the 10A setting is 0.6V.

I'm also wondering about when they specify burden voltage.  Some datasheets say mV/mA while others just mention the voltage.  When they just mention the voltage, is that the total voltage or V/A?

Thanks

[IanB]

Ignore burden voltage for the moment.

When placed in a current range, every meter will have a fixed resistance between the terminals. This resistance will depend on the range setting, being very low on the 10 A range and progressively greater on mA and uA ranges. You can measure this resistance using another meter on the ohms setting and therefore find out how much this series resistance is likely to affect your circuit if you insert the meter to measure current.

Secondly, when on the 10 A range you may find that the probe leads themselves add significant resistance to the circuit, especially if they are low quality leads.

Normally speaking, if an inserted DMM on the 10 A range stops your circuit from working, your circuit has a problem.

[ModemHead]

I would guess that if the burden voltage is specified as V and not V/A, then it is for full-scale reading, ie. 0.6V/10A = 0.06R

[PiMaker]

Thanks, Ian.  I think I was chasing down a rabbit hole.  Your comment about low quality leads got me thinking.  I'm using some leads that were around the lab and look worse for the wear.  I replaced them with some good quality leads and everything worked fine.  Sometimes things are a lot simpler than what we think!

That makes perfect sense, ModemHead.

Thanks again.