[GreenKeys] Meter shunt issue...

[Bob kb8tq]

Hi

One of the things you worry about when you design a meter shunt is how stable it is over
temperature. That (and cost) may lead you off into using “unusual” materials for the shunt.
The other gotcha is that some outfits were not as careful as they might have been with 
fluxing agents and cleaning. The combination of the two can easily create a shunt that does
have a very finite lifetime. How finite,  maybe only 100 years, maybe a lot less. I do have 
meters over in the shed that are well over 50 years old and could easily be 100. When you
dig into it, some of this stuff may have been around for quite a long time. 

Bob

> On May 8, 2017, at 9:19 AM, Kenneth Gartland <trnsrme at gmail.com> wrote:
> 
> Hi all!
> 
> Not to be too long on this topic, but I did want to share
> some good info, received from Jeff...
> 
> I had assumed the shunt coil in both meters had failed
> on account of some previous overload situ...
> 
> Both of my ma. meters had the same problem...
> 
> Jeff suggested, if an over current condition existed,
> and burnt out the shunt coil, it wud have destroyed
> the meter movement coil as well...
> 
> That theory seems to make sense...
> 
> He, further suggested the shunt could have basically
> succumbed to old age...
> 
> I know when I handled the shunt coil remnants with
> tweezers, the wire just crumbled in tiny fragments...
> 
> When I think back, a lot of my stuff sadly was not kept
> in the best of environments, and the meter shunt wires
> probably oxidized over the years, and "Died of old age"...
> 
> It is a learning lesson for me, and if some of you experience
> a similar problem, you will know the first place to check...
> 
> Thanks again for the many suggestions and advice...
> 
> I will now return to the world of Teletype...
> 
> Cheers to all!
> 
> Ken
> VE3-HMQ
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