This is not so much an installation question as a general electronics question. My ammeter on my 180 is wired so that it will show both a positive and negative current flow. Why, though, would the flow be negative? I have not paid much attention to it but sometime the flow is negative an entire flight until I turn on several heavy/flow electronic devices like the landing light.
Ammeter reads negative flow
- Thread starter dahugo
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vlittle
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- May 7, 2006
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Sounds like your ammeter shunt is in series with the battery and indicates whether current is flowing into (charging) the battery or out of (discharging) the battery. Normally, when done this way, a positive current is charging current and a negative current is discharging, so your shunt sensor wires are probably reversed.
When you turn on heavy loads, your alternator may not keep up, so the battery takes over and thats why your ammeter changes from negative to positive. FYI, these type of ammeters should always read around zero in normal conditions.
An alternative and more common installation is to put the ammeter in series with the alternator and measure the current provided. This does not provide any indication of battery charge/discharge current, but does allow you to manage your electrical loads.
Vern
Vlittle, I appreciate your response. However, I just went to www.savvyaviator.com where I upload my flight data every several months.
I spot-checked about a dozen flights over the past 6 months and spot-checked the amperage during the flights. The amperage goes shows a slow, gradual but noticeable decline from charging (10 to 12 amps thru 5 amps) to a low but noticeably increasing discharge for every flight.
After every flight, when the plane is hangared at home, we put it on a slow trickle charge.
Because of that I don't believe we have anything wired backwards.
What would cause an increasingly declining and increasingly negative amperage flow?
Could this be a sign of an alternator going out?
I spot-checked about a dozen flights over the past 6 months and spot-checked the amperage during the flights. The amperage goes shows a slow, gradual but noticeable decline from charging (10 to 12 amps thru 5 amps) to a low but noticeably increasing discharge for every flight.
After every flight, when the plane is hangared at home, we put it on a slow trickle charge.
Because of that I don't believe we have anything wired backwards.
What would cause an increasingly declining and increasingly negative amperage flow?
Could this be a sign of an alternator going out?
RVDan
I love flying!
What does voltage look like in the same time frame? It should be contstant.
Do you know how the shunt is wired in the system? If it is between the battery and the bus it should always show positive as it is indicating the current flow to and from the battery (from= negative on the gage) If this is actually happening, the alternator voltage must be below the battery voltage which means the alternator or voltage regulator has failed.
Do you know how the shunt is wired in the system? If it is between the battery and the bus it should always show positive as it is indicating the current flow to and from the battery (from= negative on the gage) If this is actually happening, the alternator voltage must be below the battery voltage which means the alternator or voltage regulator has failed.
RVDan, I'm not sure how to describe the voltage. If I knew how to insert pictures in a forum post I would provide the information. The webpage allows me to post with two attachments, so I will do that. One is with the amperage clearly registering properly, and one is with the negative amperage. You can see what the voltage does in each.
Attachments
RVDan
I love flying!
The first one looks perfectly normal on voltage and the amps look a bit jittery but without knowing what equipment is on at the time is probably just fine. Voltage sags a bit at the beginning with the extra load from recharging the battery and is otherwise quite stable.
The second graph is a problem and what is really interesting is the variance in output current with no corresponding variance in voltage. Something tells me it is a data acquisition problem, particularly if your battery isn't dying. Try the EMS ground reference maybe?
The second graph is a problem and what is really interesting is the variance in output current with no corresponding variance in voltage. Something tells me it is a data acquisition problem, particularly if your battery isn't dying. Try the EMS ground reference maybe?
Thanks RVDan,
Just to make sure we don't have a short somewhere I am going to take the cowl off tomorrow and snoop around in there. If there was a short something else would have happened and we would have smelled smoke by now, but just to be safe....
I am also going to double check wiring from Dynon to current source....
Just to make sure we don't have a short somewhere I am going to take the cowl off tomorrow and snoop around in there. If there was a short something else would have happened and we would have smelled smoke by now, but just to be safe....
I am also going to double check wiring from Dynon to current source....
RVDan
I love flying!
I don't expect a short, but rather a bad connection, one that has a bad crimp, is loose or has corrosion on it.