Ammeter/Loadmeter Sizing

[jweir43]

I'm looking at designing (for Kitplanes article) a voltmeter/loadmeter using one of those $10 digital meters and a few more goodies. The question is whether or not I can get away with using components rated for 30 amps (cheap and easy to find) or going to the 50/60 amp expensive stuff. $10 for the meter and $20 for the terminal strip seems to be a lot convoluted.\

Of course I could also say to use a thick piece of fiberglass and countersink holes for real bolts, but that seems to be a lot of unnecessary work. Besides, if you get vibration and the bolts loosen up you've got a lot of sparking going on in the machine.

Thoughts appreciated.

Jim

[Mich48041]

30 amps is fine for a small PM alternator but not for larger alternators.
A quick search on eBay and Amazon for "ammeter" results in some inexpensive digital meters with included shunts. But who knows what the quality of those shunts are. If the shunt fails, electrical power will be lost.
How about a hall effect current sensor, eBay item number:302703031130 or similar? Hall effect sensors do not compromise the aircraft electrical system.
Or how about an article about an inexpensive low voltage warning light, unless you have already done that.

[Mich48041]

Jim, here are a couple of ideas for future articles.
1. How to troubleshoot open and high resistance circuits.
2. How to troubleshoot shorted circuits.
Many people do not know the importance of applying a load to the circuit under test, especially when using a digital meter.
When it is advantageous to use the positive battery terminal as a voltage reference point.

[jweir43]

Originally Posted by Mich48041

30 amps is fine for a small PM alternator but not for larger alternators.
A quick search on eBay and Amazon for "ammeter" results in some inexpensive digital meters with included shunts. But who knows what the quality of those shunts are. If the shunt fails, electrical power will be lost.
How about a hall effect current sensor, eBay item number:302703031130 or similar? Hall effect sensors do not compromise the aircraft electrical system.
Or how about an article about an inexpensive low voltage warning light, unless you have already done that.

I should have been more specific. I could care less about the capacity of the alternator as this design is a load meter. How much current is being drawn by the aircraft system as opposed to how much the battery is charging/discharging as an ammeter will show.

The question then resolves itself as to whether measuring a 30 amp DRAW is enough or are there times when more current than this is being drawn?

Thanks,

Jim

[rv7charlie]

Some of the new auto style engine control systems can draw ~15A continuous, including the fuel pump. Add another 4-6A if both pumps run for t/o & landing. That would leave ~10A for the rest of the electrical loads.

What's the target 'market'?

Charlie

[rv8ch]

Jim, Not 100% sure this is on topic, but I use one of these from GRT:



My guess is that this is a pretty simple part, based on a bit of internet searching. I'd guess it would be cool to know how it works, and how to build one ourselves from basic components.

Thanks for your articles, I really enjoy them!

[Carl Froehlich]

A lot of options to experiment with measuring current. Here is one: https://www.amazon.com/bayite-Digita...current+sensor

Carl

[jweir43]

Originally Posted by rv8ch

Jim, Not 100% sure this is on topic, but I use one of these from GRT:



My guess is that this is a pretty simple part, based on a bit of internet searching. I'd guess it would be cool to know how it works, and how to build one ourselves from basic components.

Thanks for your articles, I really enjoy them!

This is exactly the concept; the only question that remains is how big is the hole in the center of the doughnut to pass a wire that will handle X amount of current.

I've got my choice of nearly a hundred cores and I want to make it as small as possible yet still make it capable of handling MOST of the folks that want to make one.

So the fundamental question still presents itself. How big does the hole in the doughnut need to be?

BTW, I'm shooting for a sensor using a hall-effect device and hope to keep it under $10 to build.

Jim

[GalinHdz]

This one (CS-01) has an internal diameter of .86" and can be used up to 100amps.


This one (CS-02) has a smaller internal diameter and can be used up to 50A.


FWIW: I use the CS-02 (50A) in my airplane with a #6AWG cable running inside of it to monitor instrument panel current draw on a DYNON SkyView system.