# DIY Current SHunt, what are they made of?



## ngrimm (Oct 19, 2007)

I am using 5/16" stainless steel threaded rod with nuts adjusted 1.6.33 (1 5/8") apart to display 1 millivolt per amp up to 800 amps. I read about it at http://www.fieldlines.com/story/2007/1/11/21434/1866 toward the bottom of the page.


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## peggus (Feb 18, 2008)

Shunts are made of Manganin, http://en.wikipedia.org/wiki/Manganin

Its resistance is stable across a wide temperature range, unlike other materials like stainless steel. Stainless will work fine though if you don't care about accuracy.


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## Jimdear2 (Oct 12, 2008)

rmay635703 said:


> I am looking to make a dummy ampermeter guage for my fathers ZX40, we do not need to know what amperage he is using just a visual guage to show either a lot or a little amperage much like my unlabled uncallibrated C-car ammeter.
> 
> Anyway what type of material are the shunts made of? I am thinking of buying some flat stock from the local metal place and wiring it up to my ammeter.
> 
> ...


 
Ryan,


All you need is a HV circuit that drops 50 mv. Before you spend big bucks on a shunt, do this
Drive wheels in the air.
*Be carefull because you are working with the high voltage circuit. Don't cook the cookies.*
Turn on the contactor and any other disconnect device
Spin up the wheels and using a good DVM, measure the voltage drop over each cable from lug to lug. Any cable run that has a fixed load in it that never changes like a fuse can be considered a single cable.
If you find a cable that the voltage drop is greater then 50 mv you are golden.
Again with the system powered up, connect your millivolt meter to one end of the cable and take a stright pin or equivalent and carfully pierce the insulation at various spots until you find the point of 50mv drop.
*Please remember to seal up the test point punctures with a dab of silicone.*
At thius point you have several options
Can you shorten/reroute the cable and install a new lug?
You can carefully drive a stainless steel screw into the cable and attach a suitable tab to attach the ammeter gauge lead to. Remember to seal up with shrink tube or silicone
Cut the cable and install a suitable crimp splice and shrink tube.
Some other method.

Connect your ammeter leads, one to each end of the length of cable that drops 50 mv. You have just constructed a free shunt.
You can of course add cable as well.
Remember the circuit has to have fixed loads/resistance or you will get erattic readings.

Hope you can use this. I know it works because we had to construct a field expediant shunt like this back in aircraft mecahnics school. That was 40 years ago so I may be fuzzy on this, Anyone, feel free to correct any errors I've made.


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## rmay635703 (Oct 23, 2008)

Jimdear2 said:


> Ryan,
> 
> 
> All you need is a HV circuit that drops 50 mv. Before you spend big bucks on a shunt, do this
> ...


This is what I attempted earlier, the max amperage my car uses currently is 250 amps and it goes down down down rapidly, for resolution the cables don't make enough voltage to move my cheap 10 amp shunted meter (25mv shunt type) (most are only long enough to fit between batteries)

I figured transplant a different shunt for 200amp for the 10amper shunted meter and I'm golden, it doesn't need to be very accurate so the threaded stainless steel solution will probably be fine. Also I visualize that I could vary the run length of the stainless steel stud by moving a couple nuts so if the sensitivity isn't there I can shorten/lengthen it to tune it to the cars amp draw.

I haven't checked the very long underbody cable simply because it will be difficult to route a wire to each end of it because it routes inside my framework and is tight (hole is just big enough with no wiggle room around it).

I may have to try again to see what voltage the underbody wires were at under load, I will need to plant a probe at each end and route them in the cab to really get a decent measurement, it is also possible that my cheap analog meter is fryed because my father was playing around with it and may have wired it wrong when I wasn't present, I will have to test it on a 10amp load through provided shunt (if I can find the old shunt).

Thank You For the Ideas
Ryan


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