[Boatanchors] meter shunt

[jaduffield at copper.net]

Another way to describe a 150Amp meter shunt constructed from a length of 18 ga wire is....  a fuse.

Been there done that, but only once.  Not intentional.

John  K0khz

--- infomet at embarqmail.com wrote:

From: Wilson  Lamb <infomet at embarqmail.com>
To: WA5VGO <hbrnut at suddenlink.net>, w2iy at verizon.net
Cc: boatanchors at puck.nether.net
Subject: Re: [Boatanchors] meter shunt
Date: Sun, 27 Jun 2021 21:03:23 -0400 (EDT)


What, is there someone who doesn't have experience with 150 Amp measurements! 
See: 150 amp meter shunt - Bing 
Most are impressively heavy chunks of conductor, mostly brass looking. 
You are right aboout calculating the value, except the shunt has to be very comfortable at the rated current and have enough mass to not get warm enough to change value. 
I'm sure real shunts have some design effort to maintain near zero tempco. 
I have some meter/shunt sets I sell for $20. 
If I have an extra shunt, you can have it for $10. 
There are 50mV shunts for most any current you want. 
The really tricky thing is that you can file the shunt to reduce its corss sectional area and trim its sensitivity, but only upward. 
You can use flat iron or brass bar stock to make one. 
You have to drill and tap or drill through holes for attaching the wire with husky bolts. 
You aren't dealing with much resistance, so you want to be sure there's no chance for the terminals to change their connection quality. 
WL 
    

-----Original Message-----

From: WA5VGO <hbrnut at suddenlink.net>
To: w2iy <w2iy at verizon.net>
Cc: boatanchors <boatanchors at puck.nether.net>
Date: Sunday, 27 June 2021 8:05 PM EDT
Subject: Re: [Boatanchors] meter shunt

https://skycraftsurplus.com/products/dc-ammeter-shunt-150-amp-for-50-mv-movement.html

> On Jun 27, 2021, at 6:50 PM, Michael Tortorella via Boatanchors <boatanchors at puck.nether.net> wrote:
> 
> Folks, I am holding a 150-amp DC meter whose native full scale is 50
> millivolts. If I have done my Ohm's Law correctly, the required shunt is
> 0.00033 ohms. Not in the Mouser catalog :-) :-) Is this just like 8 inches
> of #18 wire or something? Advice welcome. aTdHvAaNnKcSe and 73, Mike W2IY
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