Ammeter Readings Fluctuate Wildly

[swbeyer]

My CTLS ammeter readings have always fluctuated greatly and seemingly randomly. Typically it ranges from around -8 to +12, but occasionally goes outside that range, primarily above it. In the past year, evidently the fluctuation range has become even greater because now I occasionally get high current warnings that last just a second or two. The dynon triggers this warning (red light and sound alarm) when the ammeter reading spikes over 25. Should I simply increase the alarm threshold to 30 ? Is 25 really a critical value ?

The root question is why should the ammeter fluctuate at all ? I've flown Skyhawks and Skycatchers and the ammeter reading is rock solid at one value. That makes sense to me. It makes no sense that the electrical current would fluctuate wildly. Is the Dynon ammeter giving invalid readings ? Would another ammeter show a constant value ?

On a recent flight of 2 hours I had roughly 12 instances of the high current alarm warning getting triggered, but on each occasion it went off by itself within 1 or 2 seconds. I've never had any other symtoms such as a blown fuse or other electrical problem. It's happened perhaps a 100 times over my last 30 hours of flight.

 

[skysailor]

Always start with the easy things first. Have you checked the connections at the shunt? Check them all but it seems more likely from your description the small indication wires may have a loose/bad connection. If the battery is staying charged the big wires are probably fine but you might as well make sure since you are going to be there anyway.

 

[swbeyer]

Thanks, I'll have a mechanic check the wiring.  Should the ammeter show a constant reading as in the Skyhawk and Skycatcher Garmin displays, or is a fluctuating reading normal for the Dynon display in my CTLS (Rotax 912 engine) ?

 

[jakej]

R59

Those symptoms are definately due to a 'bad' connection, perseverance will find it

Jake J

 

[skysailor]

Just like Jake says, the problem is going to be with a bad connection. If you are not seeing fluctuations in the panel lights or landing light, you are probably getting clean power and the fault will be found in a bad connection. The Skyview accurately reports the input given to it but when you find this problem you will have the steady readings you are used to. Check the connections and I think you will find your problem.

 

[swbeyer]

I think the ammeter readings are very steady until I flip the generator switch on, but I'll have to verify that when I go flying again in the next week or two.  I think that would suggest the avionics circuit is fine but when the generator comes online (connects to the circuit) it causes those ammeter fluctuations for some reason.

As you may know the Rotax 912 has no alternator, but instead has an integrated generator.  It runs whenever the engine is rotating and I presume the switch merely puts it online to the avionics circuit so the battery can charge.

 

[dynonsupport]

I think the ammeter readings are very steady until I flip the generator switch on, but I'll have to verify that when I go flying again in the next week or two.  I think that would suggest the avionics circuit is fine but when the generator comes online (connects to the circuit) it causes those ammeter fluctuations for some reason.

As you may know the Rotax 912 has no alternator, but instead has an integrated generator.  It runs whenever the engine is rotating and I presume the switch merely puts it online to the avionics circuit so the battery can charge.

We have had customer reports that the Rotax generator is, simply, electrically noisy. We haven't found a solution to this issue.

 

[jakej]

I think the ammeter readings are very steady until I flip the generator switch on, but I'll have to verify that when I go flying again in the next week or two.  I think that would suggest the avionics circuit is fine but when the generator comes online (connects to the circuit) it causes those ammeter fluctuations for some reason.

As you may know the Rotax 912 has no alternator, but instead has an integrated generator.  It runs whenever the engine is rotating and I presume the switch merely puts it online to the avionics circuit so the battery can charge.

In that case I'd also add an Electrolytic capacitor --- http://www.bandc.biz/electrolyticfiltercapacitor.aspx into one of the genny output wires, better for the radio too

Jake J

 

[swbeyer]

Ok, thanks for all the comments.  I'll verify that the ammeter fluctuations occur only when the generator is online to the circuit (I'm fairly certain that's true).  If so, I'll check with CTLS support as whether they're aware of this issue.  I'll also then check with ROTAX engine support to get some comments from them.  Surely they must know if their generator causes "electrical noise" and ampere fluctuations.

I'll post back whatever I find out ......

 

[jakej]

I should have mentioned also that I've noticed a few LSA aircraft from Europe have electrolytic capacitors fitted as standard equipment.

Jake J

 

[swbeyer]

I was out for a flight a few days ago and can confirm, as per my prior posts, that the ammeter only fluctuates when the Rotax generator switch is turned on.  So indeed there seems to be some sort of incompatibility between the Dynon ammeter and the current generated by the Rotax.

I will now try to survey some other Rotax plane owners to establish whether they are all also seeing the ammeter readings fluctuate.  Maybe everyone is seeing this ?

I'll post back when I learn more about the issue. 

 

[Roger_Lee]

Mine fluctuates too in my Flight Design CT, but it has fluctuated in other vehicles that I have driven too.

 

[swbeyer]

How much does your Flight Design CT ammeter fluctuate ?  Is it about the way I described it in prior posts ?  Have you ever gotten a high current alert ?

 

[Roger_Lee]

My Ct fluctuates between -2 to +3. Your fluctuations are too much. A bad connection some where. The CT is famous for a bad ground. I'm a CT service center. Give me a call and I'll tell you where to look and tighten them.
520-349-7056

 

[swbeyer]

Thanks Roger.  I spoke with Flight Design USA today and they had me send them an email with a detailed description.  So I'll await to hear back from them before giving you a call ..... thanks again !