5 wire shunt

[throbscottle]

I've been looking at some nice 500μΩ shunts from Vishay, and a lot of them have a 5th leg - so you have the two power terminals, the two sense terminals, and an extra connection close to one of the power terminal holes.

I've found out it is used in power measurement to measure the voltage at the shunt connection, but I'd like to understand how it is used. Can anyone enlighten me?

Thanks in advance, as always

 

[ericgibbs]

hi,
Have a read thru this link.

https://electronics.stackexchange.com/questions/22170/why-shunt-resistance-has-3-line

E.

 

[MrAl]

Hi,

Nice link Eric. That explains it nicely and even shows some pictures of the internal construction.

If i was to build one i would probably put the A wire connection as far from the sense element as possible, so that would put it on the far left of the diagrams. But apparently it works ok as it is if that's the way they make them normally.

 

[throbscottle]

I read the link before posting, read it again now. Still struggling... Maybe I'm being lazy but I understand the "why" but not the "how" of lead "A". I'll have a play with a mock up in LTSpice see if it helps...

Thanks folks.

 

[ericgibbs]

I read the link before posting, read it again now. Still struggling... Maybe I'm being lazy but I understand the "why" but not the "how" of lead "A". I'll have a play with a mock up in LTSpice see if it helps...

Thanks folks.

hi throb,

The circuit in that link is a Current measurement circuit only,.

It gives a Vshunt output voltage proportional to the current flowing thru the shunt resistor section by measuring the voltage drop across terminals B & C.

The 'A' terminal, measuring the Vsrc and the Vshunt output would have to be connected to another circuit that would give the scaled Product of the Vsrc and Vshunt in order to measure the Power.

E.

 

[throbscottle]

Ahhhh - that makes much more sense! Thanks