i need an accurate MV meter

[mobile_bob]

anyone got a line on a millivolt meter

i need a meter that is good to a resolution of .001volt with an accuracy of +/- .001v

does anyone have any idea where i can get one?

i am so tired of having 6 friggin meters, 3 being various flukes, and none of them agree within
+/- .020volts sometimes, other times .050volts, still others whatever you want.

how the hell does one measure between .001 and .100volt

i have a precision shunt, 50amps at 50millivolt and just order another that  is 100amps at 50millivolts

i have a scope, is this what i am going to have to use to attain the needed accuracy?

i have one nice analog meter, but i am concerned with it not being true rms, or how it reacts to harmonic distortion.

getting frustrated here, it would be really easy if i had a killawatt meter that would operate from 10-128volts ac, but they start
to drop out at about 95 volts or so,

coming from a background where +/- 10amps in a charging system is good enough, and +/- 100amps in a starter is good enough.

inquiring minds want to know, dammit!



bob g

[rcavictim]

getting frustrated here, it would be really easy if i had a killawatt meter that would operate from 10-128volts ac, but they start
to drop out at about 95 volts or so,




bob g

That is my biggest complaint wih the kill-a-watt meter.  Problem is the internal power supply to run the meter circuit is the same as the power source being measured.  If one could go inside the thing and hack it so the instrumentation was powered from a outboard battery or maybe a wall wort then maybe you could do more stuff like we types do often.  Example.  Slow the genset down so that just 30 Hz is coming out and be able to get the same data on less volts, frequency, amps, and power in watts instead of a blank screen.

It might be easy to do.  I only own one of these meters just now and wouldn't mind getting another.

[mobile_bob]

my biz partner reminded me that our hand held automotive scopes are good at measuring millivolts,
so i guess i will be trying to use on of them tomorrow  in testing.

of course it doesn't help much my not reading the spec's on the new shunt i order and just started to use
it is a 50mv at 50amps
and all the while i am trying to read 100amps thinking it was a 50mv at 100amp shunt!!!

sometimes i am my worst enemy



as for the killawatt, maybe one of our electronic guru's can take the time to modify one for use with a seperate power supply?

any volunteers?

no pushing to get to the front of the line now!



bob g

[elnav]

Bob since you talk about shunts I assume you are only trying to read  DC.  There was a product from Cruising Equipment - later  a part of Heart Interface - called a LINK.   LINK 10 was a single bank stand alone instrument Link 20  a stand alone dual bank  and Link 1000  & Link 2000 were companion instruments that included on off control of a big inverter.  The Link 2000R included a 3 stage regulator for an alternator as well as the  dual bank inverter charger  section.  These instruments would use a 500 amp = 50 millivolt  shunt so to read a 1 amp resolution the meter had to read in micro volt increments. It is essential to use  twisted pair wires from shunt to meter or you  could introduce induced errors. #18Ga wire with 5 twists per foot is adequate between shunt and digital meter.
Blue Sea equipment in Bellingham WA now sell a shunt with the conversion electronic chip mounted right on the shunt, that couples to their regular meter  products.
Link10 etc. can still be found on eBay.  Cruze Pro, Xantrex,  Victron, and  Mastervolt  all sell  battery monitor equipment using similar technology.  Or you can roll your own by altering the internal shunts  used in the production meters. 

[elnav]

Bob have a look at this   -   http://www.murata-ps.com/releases/mps336a_dmu-30.html?feature=dpm
We often used their products  for custom made  panel meters.

Concerning DC -DC converters
Have a look at Victron Energy systems <  www.victronenergysystems.com > go to DC-DC converters Orion series.  Last December we needed a 24V top  12 V 20 amp converter the price was  around $90   I just double checked  and they do have 48V to 24V  models.

North American distributor is in Maine but a WA state dealer is Boat Electric in Seattle.