Drift in Measured Fuel readout

[bernardsv]

I am seeing drift in the readout of my Capacitive senders.
Today when I first turned on the Master Switch, Fuel Computer Quantity read 25.2, Measured Fuel in Tanks read 19.5. Individually, the tanks read 10 and 10 Gals. Over a ten minute period, the Measured fuel Quantity increased to 23.9. Individually, Left and Right tanks increased to 11 and 11. The engine was not running. A battery charger was connected to my battery for the ten minute period.

Two questions.
1. What is causing the drift in both Left and Right readouts? They both trend upwards.

2. Why does the sum of the two tanks not equal the total 'Measured Fuel'?

 

[dynonsupport]

Are you using capactive sender converters that Dynon makes, or a capactive probe by another company?

Is this new behavior after it working, or is this a new plane?

What software version are you on?

Did you power up the capacitve probes after SkyView was turned on?

To answer the "non matching" question, we always round down the fuel displayed on the EMS screen, so that it always under-measures which is the safe thing to do. So if you have 11.95 and 11.95 gallons in each tank, we'll show "11" in those tanks. However, the "measured fuel" page does not round, as it is trying to be as accurate as possible when on the ground. Thus, 11.95+11.95 is 23.9.

 

[bernardsv]

Are you using capactive sender converters that Dynon makes, or a capactive probe by another company?
Dynon senders. Purchased three years ago. They've been in use for one year. Both senders share a common power source. How dependent is their output on power supply stability?.

Is this new behavior after it working, or is this a new plane?
The plane is one year old. I'd not seen drift until this event but I've not previously observed these displayed values for longer than perhaps one minute.

What software version are you on?
12.2 running on replacement touch screen EFIS installed one week earlier.

Did you power up the capacitve probes after SkyView was turned on?
Power is applied simultaneously.

 

[dynonsupport]

Were you running 12.2 before your upgrade?

We added more filtering to fuel levels in 12.0 to prevent alarms when the fuel was low and sloshing around. We have had some reports that it might be too long with capacitive senders and we are reducing this some in the next release. It should only be an issue if your capacitive senders are powered on after SkyView is fully booted however.

The converters are not sensitive to aircraft voltage.

 

[bernardsv]

Were you running 12.2 before your upgrade?

Yes, I've been running 12.2 since its release.

 

[bernardsv]

When turning on power today, the "Measured fuel" in tanks read 22.4 on my Left EFIS while the Right read 24.0. Both units are SV D1000T, running 12.2. Curious as to how such an anomaly can be explained.

 

[dynonsupport]

You turned the screens on at different times.

Fuel level is calculated locally by each screen from the voltage sent by the fuel level sender. There's also a 1 minute filter to prevent slosh from causing issues with fuel readings. If you turn one screen on while the sender is at 25 gallons and the other on when it's 23 because the fuel is sloshing around, then it will take about a minute for them to both read 24.

 

[bernardsv]

Power is applied to both screens and capacitive senders simultaneously. However since each screen has a slightly different boot time, and the senders are drifting at power-up, this would explain how each screen displays a different initial fuel quantity. I've not yet observed the displays over a longer period to confirm that they eventually equalize.

 

[bernardsv]

When I 'Accept' measured fuel quantity, the warning message clears but this condition is not saved when I power down. The warning message returns when I turn power back on. Since I don't have a backup battery, I turn off each screen using button 1. According to the instructions, this is an 'orderly' shutdown which should include saving fuel quantities to memory.
An explanation of this behavior would be appreciated.

 

[dynonsupport]

It should save the fuel on board. When it powers up is the fuel on board the old number, or the one you accepted? Trying to figure out if the alert is wrong, or if it's not saving the fuel quantity.

Can you give us some more information about the system? How many screens, what software version, and how soon after you press accept are you shutting down the system? Does it happen every time, or just sometimes?

 

[bernardsv]

It should save the fuel on board. When it powers up is the fuel on board the old number, or the one you accepted?


Can you give us some more information about the system? How many screens, what software version, and how soon after you press accept are you shutting down the system? Does it happen every time, or just sometimes?

The quantity I accepted is displayed.
Two screens running 12.2 sw.
Shutting down about one minute later.
This happens every time.

 

[dynonsupport]

Does it do it if you shut the screens down in a different order or boot them up in a different order?

What if you boot one, accept, shut down, and then boot just it again?

If you can get it to happen and then pull a datalog from both screens we can probably figure it out too.

 

[bernardsv]

What if you boot one, accept, shut down, and then boot just it again?

I did this, both screens now function correctly.
Thanks for your help.