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The Philpott · 15th Jun 2021, 10:54 am

Yes, that's it! Thanks wave-solder/Ian. I hadn't come across a shunt which is used on a current range before, hence the caution.

The battery's dropped a little so the test current is now a measured 6.2A using the meter alone. Then using the external shunt, i'm getting 5.8A on both the 'new' 24A range, and on the press-button 12A range. The cutout isn't achieving perfect contact while using the external shunt in this way, (which could explain the shortfall, it needs attention) but it's interesting this fault didn't show up when using the meter on it's own.

As the dissipation is shared across both internal/external shunts, i suppose the full range up to 24A is viable. So this accessory allows a Model 40/47A/48A to compete with a Model D in one respect at least!

(crossed with Al's response- 24A then becomes 12A range with DB2 button pressed)

Dave

15th Jun 2021, 10:54 am	#6
The Philpott Dekatron Join Date: Aug 2016 Location: Colchester, Essex, UK. Posts: 4,108	Re: Avometer Mod.47A DC current shunt oddity Yes, that's it! Thanks wave-solder/Ian. I hadn't come across a shunt which is used on a current range before, hence the caution. The battery's dropped a little so the test current is now a measured 6.2A using the meter alone. Then using the external shunt, i'm getting 5.8A on both the 'new' 24A range, and on the press-button 12A range. The cutout isn't achieving perfect contact while using the external shunt in this way, (which could explain the shortfall, it needs attention) but it's interesting this fault didn't show up when using the meter on it's own. As the dissipation is shared across both internal/external shunts, i suppose the full range up to 24A is viable. So this accessory allows a Model 40/47A/48A to compete with a Model D in one respect at least! (crossed with Al's response- 24A then becomes 12A range with DB2 button pressed) Dave