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Volt amp meter problem

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wjyates

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I bought a volt amp meter for a project I'm working on. problem, I have no access to the - load wire only the + wire
pic attached. would it be possible to use the shunt on the + side. or replace the shunt with a current loop so I can then read current off the + side or should I just buy one that will work on the high side

51DxHv6JdYL.jpg
 
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You need to check the meter, some measure the difference in voltage accross the shunt, others from ground to the non ground side of the shunt, or maybe the + leg of the supply to the load.
Do you have a suggested wiring diagram for the meter?, is the shunt in the + or - line?, if the + then your idea may not work without extra circuitry.
 
can you guys not see the diagram I posted. anyway it shows the shunt on the - side. but like I said I have no access to
the - wire. may have come up with my own idea. I have a sencing circuit from another project. I'll run it off a shunt from the + side and then to my meter
 
Yes that might work, the o/p from a differential amp amplifying the v drop across a shunt in the + side shunt can be fed to the meters i/p for a shunt that would normally be in the - side.
The i/p impedance of the meter is probably high enough for an op amp to drive.
 
hay doc, it seems like you,re the only one paying attention. just to let you know my project now works great. with a little tweak of the output resistor on my sensing circuit it now reads within .1 of an amp + or -

thanks for your input
 
No problem, I'm sure theres more than just me paying attention, must be a quiet day.

0.1a isnt brilliant accuracy wise, it depends what you want to do if your motor pulls a lot of current it might not matter, a % or so is probably the best to be expected from most meters like this.
 
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