FAS settings

[Sp1k3]

Hi Guys,
When testing the new current sensor from FrSky I found that it is +10% off target. So I did some research in the forum and found this post viewtopic.php?f=7&t=4&p=86325&hilit=FAS+offset#p86332
but it is rather old.
Just so that we understand we eachother, lets take an equation y = a*x+b is the FAS offset = b or a? And if the FAS offset is b then how do I program a? Is there any new feature for that? Or is FAS offset =a? In which case I should set it to -10% and this would solve my accuracy issue.
Thanks Sp1k3

[MikeB]

The FAS offset value is 'b'.
If you do need to scale the FAS value then have a look at the "Scalers" (under the Globals menu index).

Mike.

[Sp1k3]

Thanks Mike,
But for the sake of simplicity, wouldn't it make more sense to have an "FAS multiplying" factor as well in the next release?
Clearly there are other solutions, but this would be such a simple thing to add in the telemetry window. And quit frankly said I think it would be useful to many. Just a thought.
In any case thanks for the tip.

-One more question concerning the FAS sensor, I have the 150A one and I was wondering if the sensor on board actually calculates the mAh and sends it to the Rx or as I believe what it is happening, the sensor only sends the current, and the radio is then integrating it to get the mAh?
BR
Sp1k3

[MikeB]

How are you determining the sensor is 10% out?
I'll think about adding a FAS multiplier.

Yes, the sensor just sends the current and this is integrated in the radio to give mAh.

Mike.

[jhsa]

With a Scaler as Mike said, you can multiply, divide, offset, etc the value from ANY source, whether is telemetry or not. If you just need to multiply it is even easier and you can give the scaler another name that you use in the mixer, Voice Alerts, Logical switches, etc. In my opinion making duplicate settings makes things less user friendly/more confusing, and also makes an already super crowded menu (Telemetry menu) even more crowded.
This kind of situations are the reason the Scalers exist, so we might as well use them. And if we have problems with the calculations (I always do ) we ask here on the forum and someone will help.

Just my 2 cents

João

[Sp1k3]

@ Mike
I found that out by measuring the mAh from the FAS sensor and from a second sensor in series, then I confirmed the second was right when I recharged the battery to full charge. I'm using it on a car so that values change pretty quickly and the sampling time on the radio is pretty slow so it could be an error caused to the slow integration or it could be to the different current readings.
Let me run one more test which high current 40A or so to see if the current value is off or if it is just an integration issue. Typically the mAh is calculated on board then the sampling frequency of the integration is much higher and more accurate, but here I suspect that the radio is doing this integration which could be the cause of the issue.
Now I just need to figure out a test bench for this, my wife is going to be thrilled
@Joao
if the current measurement is accurate then I agree, but if it is a common problem then I think that such a modification would be simpler for the basic newbie user like me.
Sp1k3

[jhsa]

The problem is that might not only be a multiplication problem? perhaps you also need to apply some offset? Maybe the problem is caused by component tolerances? Then the scaler gives you more options to adjust to a correct value..

João

[Sp1k3]

Alright measurement results show that the current is slightly higher than what is measured, but not 10% as measured by the capacity difference.
However what I observed is that the current value is oscillating a lot, while the other 3 ampmeters I had were reading steady values. SO I think the problem is really the fact that the sensor itself doesn't really read steady but is constantly oscillating around the target value not very accurately...
I guess there is no way to correct that.
But at least this means that the measured value is pretty much fine as is.

Sp1k3