What is a Shunt? Need a analogy Please!

[ron sterba]

Starting the wiring on my 9A. Shunt what is it? how does it work?What benifits of having one? Would like your ideas on a analogy if you please.

Ron in Oregon 9A

[RV6_flyer]

Originally Posted by ron sterba

Starting the wiring on my 9A. Shunt what is it? how does it work?What benifits of having one? Would like your ideas on a analogy if you please.

Ron in Oregon 9A

Here is what Google has to say when searching on "what is a shunt".

http://en.wikipedia.org/wiki/Shunt_%28electrical%29

I would like to suggest reading what it says under:
Use in current measuring

[BobTurner]

A shunt is a low value resistor. A conventional meter cannot handle 50 amps, so you put it in parallel with a shunt. Maybe 0.5 amps flows thru the meter, all the rest of the current flows thru the shunt. The meter is calibrated with the shunt so it reads 50 even though only 0.5 amps is flowing thru it.

An alternative is to use a Hall sensor. this detects the magnetic field around the wire, and can handle large currents like 50 amps without using a shunt. I prefer this approach, one less connection to make.

[Greg Arehart]

Bob,

Suggestions on cost/where to get a Hall sensor? Do you know if they will work with, say, the Dynon (which is apparently set up for using a shunt)? Weight, compared to a shunt? I agree that such a sensor would be preferable to the exposed (in most cases) shunt.

Thanks,
Greg

[BobTurner]

GRT sells them, they come standard with the GRT EIS. $60 I think. I don't know if Dynon supports them, they do take a different circuit than a shunt.

[Bob'sRV6A]

per Dynon Support:

We slip-streamed multiple AMPS monitoring capability into SkyView recently by adding support of the GRT CS-01 Hall Effect Current Sensor which connects to one of the three enhanced general purpose inputs - Pins 8, 22, or 31. A (one, or more) CS-01 can be displayed on the EMS page in addition to the AMPS Shunt.

Of course, you can also display AMPS on the EMS page that is being generated by the optional VP-X.
? Last Edit: Dec 16th, 2011 at 3:25pm by Dynon Support ?
they also wrote:
The CS-01 is a hall effect current sensor that GRT Avionics sells. Connection and configuration instructions are in the latest SkyView Installation Guide on our site.

[az_gila]

Analogy - use flowing water to represent electricity flowing.

Imagine a pipe with water flowing in it.
Put a slight, but known, restriction in it.
Now, the pressure drop across that slight restriction will be proportional to the water flow rate.

This lets us use pressure - which is easier to measure - to determine water flow rate.

Back to electricity --

The shunt is just a slight, but calibrated, resistor inserted into the line that we want to measure current (=water flow.....)

[ccsmith51]

You are measuring the small voltage drop across the shunt. Typical shunts will have a 50 millivolt or 100 millivolt drop across them at rated current. They are very linear so are very accurate from 0 to rated current.

I have a 30 ampere, 50 millivolt shunt ( http://www.aircraftspruce.com/catalo...metershunt.php ) in my RV-4. It is connected to a meter on my panel that displays 0 - 30 amperes. But because the shunt signal is a voltage, 0 - 50 mV, the meter is actually a voltmeter that has a display that reads in amperes.

So, technically you are not directly measuring current, instead directly measuring voltage but coverting it to a calibrated current reading....

[az_gila]

Originally Posted by ccsmith51

You are measuring the small voltage drop across the shunt. Typical shunts will have a 50 millivolt or 100 millivolt drop across them at rated current. They are very linear so are very accurate from 0 to rated current.

I have a 30 ampere, 50 millivolt shunt ( http://www.aircraftspruce.com/catalo...metershunt.php ) in my RV-4. It is connected to a meter on my panel that displays 0 - 30 amperes. But because the shunt signal is a voltage, 0 - 50 mV, the meter is actually a voltmeter that has a display that reads in amperes.

So, technically you are not directly measuring current, instead directly measuring voltage but coverting it to a calibrated current reading....

I never said it did...

The shunt is just a slight, but calibrated, resistor inserted into the line that we want to measure current (=water flow.....)

I just said where it is located...

[ccsmith51]

Hey Gil, i wasn't directing the "you" in my post to you. I meant "you" to be anyone reading my post.