R

ron sterba

Well Known Member
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
 
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.
 
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
 
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.
 
Skyview now supports it.

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.
 
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..:)...)
 
Last edited:
But you are not measuring current with a shunt...

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/catalog/inpages/umaAmmetershunt.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....
 
ccsmith51 said:
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/catalog/inpages/umaAmmetershunt.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....
Click to expand...

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...:D
 
Hey Gil, i wasn't directing the "you" in my post to you. :p I meant "you" to be anyone reading my post. :)
 
Greg Arehart said:
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
Click to expand...

To get rid of the possible voltage short on an exposed current shunt, install the shunt in the ground wire.
 
ccsmith51 said:
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/catalog/inpages/umaAmmetershunt.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....
Click to expand...

Yes. You are reading the voltage drop across the resistor. Remember ohms law. V = I * R or I = V / R. In other words, the current is directly proportional to the voltage reading and the mV meter can be calibrated to read AMPS.

The Dynon EMS D10 sensor kit comes with a 60 Amp 60 mV shunt. How do I know this, I purchased one from Stein Air at AirVenture 2012 and will be installing it shortly.

You are correct in many being 50 mV. I have 5 or 6 of them in my spare parts box and all are 50 mV. The spare ones I have all are different current values but all the same 50 mV voltage.
 
RV6_flyer said:
.....

The Dynon EMS D10 sensor kit comes with a 60 Amp 60 mV shunt. How do I know this, I purchased one from Stein Air at AirVenture 2012 and will be installing it shortly.

You are correct in many being 50 mV. I have 5 or 6 of them in my spare parts box and all are 50 mV. The spare ones I have all are different current values but all the same 50 mV voltage.
Click to expand...

Or, if you don't have a big alternator, a 50 Amp, 50 mV shunt would keep the Dynon EMS happy...:)
 
Thanks Gary it was good reading in WiKi. Learned a lot. Every new builder should read it! Bob it was very helpful also that I'm a SKYVIEW 10" guy. ( one display). With a alternate, the HILL sensor sounds like a good way to go with my DYNON unit. Bob thanks for the DYNON configuration, very helpful! Gil I like the the down to earth analogy to make the connection.It rounds out my overall picture & functionality of the SHUNT. Chris, thanks did look up that shunt in A/C Spruce. Nice picture. I'v seen them under cowlings on firewalls and wondered about them. I went to Grand Rapids Technology/ Avionics and found a picture of the CS-01 for $70 bucks. Range is +/- 100 amps. So I'm on my way over another hurdle in this 9A project.
Thanks again everyone. Much appreciated.
Ron in Oregon
Vice Pres EAA chpt 292.
 
What's the value of the shunt? For example, my VP-50 reports, say, 14.3 volts with the alternator on, and it reports my total amps being drawn. What is the important information I'm missing out on by not having a shunt installed?
 
LettersFromFlyoverCountry said:
What's the value of the shunt? For example, my VP-50 reports, say, 14.3 volts with the alternator on, and it reports my total amps being drawn. What is the important information I'm missing out on by not having a shunt installed?
Click to expand...

Bob,

The VP-50 has the current sensing function built in. So with a VP-50 installed there is no need for a shunt, unless you want to add a dedicated meter to show amps.
 
You must log in or register to reply here.