Fuel Calibration Issues - Tank 3 & 4

[jwachman]

Firstly, I have worked through the forum site and can't find a reference to my exact issue, hence I am adding my own post.

Configuration. EMS D-10, EFIS D-10A and HS34. All running version 5.0, and woking fine on the DSAB. Main tanks connected to EMS, Tank 3 & 4 connected to HS34.

HS 34 tank connections function, and the sensors register, but I keep having problems.

All tanks are 40 ltrs, all have identical sensors.

The main tanks are calibrated correctly, and during the calibration I noted the sensors start at a reading of about 135 and reduce at about 15 intervals to finally read about 30. Each addition of 5 ltrs calibrates successfully, and there are no bumps in the calibration.

Now on to the tank 3 & 4 problems. The HS34 is correctly connected and the 1K resistors are fitted and connected to the 5V exciter line. (This had been the problem in a previous post of mine).

However, when I run the calibration the sensor initially reads about 35, and drops 2-3 with each addition of 5 ltrs. Each time I add 5 ltrs the calibration states "no fuel was added, did you want to accept this reading" (or similar words), I select Yes. This happens for each addition of 5 ltrs. Eventually, I fill the tank and select full. The calibration says that it works, but when I next apply power, the tanks have CAL above them, and need re-calibrating.

It appears the issue is related to the fact the sensor only reads 35 to 5, not 135 down to 40, as per the main tanks connected to the EMS.

I can't understand why the input via the HS34 doesn't function the same as the main tank.

Can you please assist. I have completed all the fault inding I can.

Many thanks.

Jon :-/

 

[DBRV10]

Check your sensor connection, you may be off the wrong end of the Potentiometer.

Sounds like the more you put in the voltage is dropping (inverse to what the other is. The sweeper is the analogue input and the supply is the "end" of the pot, so swap ends and see what happens.

Just a wild guess!

 

[jwachman]

David,

Thanks for your info. The system is connected correctly. I can test the system with the inboard tank fuel sender, and another I use for system testing. In all cases when connected to the HS34 the readings are different. They still function in the same manner - the larger calibration number for empty, getting smaller for full.

It shouldn't matter if the sender is "upside down" as it is the difference that matters.

The issue here is that when connected to the HS34 the 'range' from full to empty is reduced.

Can't work this out.

Cheers

Jon

 

[dynonsupport]

The fix here should be simple. When hooking a fuel sender to the HS34, you should use a 200 ohm pull-up to 5V, not a 1K. Using a 1K will give you a much smaller range, since the fuel sender is only about 100 ohms.

I see the EMS install manual recommends a 1K, but we should probably change this.

 

[jwachman]

Thanks for your quick reply. I will action this and add a post to this when completed, to detail the results.

Cheers

Jon

 

[jwachman]

Dear Dynon,

I have half of the problem solved. I changed to 200 ohm resistors and the scale has improved to about 135-40.

I then calibrated the tanks and all seemed to work very well.  I then disconnected the tank senders at the wing (as I have folding wings).

Now I have turned the system back on and tanks 3 and 4 now flash CAL. Tanks 1 and 2 are fine.

Why does the system keep dropping the calibration results?

Can you please assist.

Many thanks

Jon :-/

 

[dynonsupport]

Just to be clear - you did calibrate tanks 3 & 4 individually, correct? After calibration, did you change any of the GP inputs away from fuel tank 3/4? And which GP inputs are you using?

One thing to try would be to calibrate, then manually shut the EMS down by holding the right button (rather than using master).

There's also a chance (we'd have to research this) that the HS34 GP inputs won't store a calibration properly (this would be a bug, but still a fact of life if it's the case). The solution here would be to use the EMS GP inputs instead, and move whatever is on them to the HS34.

 

[jwachman]

Thanks for your quick reply.

So on to the answers:

Yes I have calibrated the tanks seperately, and have not touched the GP inputs nor configuration.

I will try shutting the EMS down seperately this weekend and check.

Now the GP inputs - Here I don't have much flexibility.

There are 3 GP inputs on the EMS, I am using two of these for the Rotax CHT, and have no option to move these to the HS34. Apart from the physical problems of changing the wiring in a completed aircraft.

Therefore, with only one GP input left on the EMS, I thought it better to use the inputs on the HS34.  I used HS34 GP inputs 1 and 2.
If there is a bug, I would rather wait for a fix than change the wiring.

So there appear to be two actions. I need to try shutting the EMS down seperately, and if possible you could see if the may be an issue with the HS34.

I'll update this on the weekend.

Many thanks.

Jon

 

[jwachman]

Dear Dynon,

Well I have finished the fault finding, and the issue appears linked to the HS34.

I have a spare fuel sender that allows me to conduct multiple quick calibrations. Emptying the tank each time would be a killer.  I manually move thew spare sender with each 5 litre addition at about the same amount as when fuel is added into the tank.

All the calibrations work fine, so long as the power is left on. After being told the calibration is succesful and returning to the fuel tank page, i can use the spare sender to test the tanks. This works fine, all cautions and warning work as well. Then sender works for tanks 1 & 2 as well - no issues.

The issue comes when the power is turned off. I have tried both ways, just shutting down the EMS and turning the battrey off.

Either way the calibration is lost. When the EMS boots up again both tank 3 and 4 show CAL. Nothing I do stops this happening.

As I explained below, I can't rewire the system as I only have one spare EMS GP input.

I am content to wait for a 'fix' for the software.

Please let me know what you think can be done to overcome this problem.

Many thanks

Jon :-/

 

[dynonsupport]

We've added that to our list of bugs to be investigated, but it might be a bit before we have an update on this.