[jtrout19]

Hey guys So a gentleman added some stuff to the wiki about the HKPilot Power VI PDB for me. It has a built in V and I sensor. I had to calculate values for the thing since it is a 120a and wiki only covers 180a 90a and 45a. Thing is I finally got around to double checking my Current value last night and it was way off. I used a fluke multimeter and found at rest my quad only pulls about 500mA
The setting I had calculate had it pulling 1.75a. So using the value from fluke I came up with a new current value of 12.6. Which would mean if my calculations are correct that it has a current sensitivity of 79.36mV/A. This to me seems to be a value more appropriate for a lower amperage sensor and now a 120a. Any Ideas on this?

[f5soh]

https://librepilot.atlassian.net/wiki/display/LPDOC/Configure+a+Current-Voltage+sensor#ConfigureaCurrent-Voltagesensor-SettingFlightBatterySettingsProperties

Maybe related:



Last test to do is flight and compare the energy consumed with the energy you put in battery after charging.
I usually set the factor for a little more energy displayed in osd (5/10%) so that safe to go back to the base and protect the battery.

[jtrout19]

Ok i will do this and report back. I dont want the wiki to have wrong info that is why i am double checking.

[TheOtherCliff]

It's more important for it to measure the high current accurately.

I would use my most accurate high current amp meter and make sure it was accurate at the top end, or at hover power, or what ever power setting you use most, or the highest value the meter can show.

Do some current sensors have a low current setting as well?  Like high speed and idle mixture needles on a nitro motor?

Be aware that your standard balancing lipo charger will tell you that it puts in more juice than it takes out if you do a balance charge from storage voltage, then a storage from full charge.  There are a couple reasons.  Some charge energy comes out as heat and the balancing process is not measured correctly by the charger.

[jtrout19]

Fair enough i use a fluke meter so that is what will get used to do the measurement.

[TheOtherCliff]

That probably only goes to 10 or 20 amps?  So just use enough throttle to load it to that during testing / calibration?

Internet wisdom has it that you might consider buying a hobby "watt meter" which generally does amps, and usually up to 100 amps or so.  These are helpful to make sure you are not over amping your motors when you are learning and experimenting with different sized props.

[jtrout19]

Good point didnt think about that. I will get a watt meter

[HighAltitude]

I "inherited" a Team Blacksheep 50 A current sensor in a box of miscellaneous stuff from a friend.  I'd like to use it with Revo boards in my quads.
Does anybody know the current factor for this item?
Thanks

[TheOtherCliff]

A little experimentation should get you a number. 

Start with a reasonable number and if it is off by a factor of 2.173 you multiply or divide your guess by 2.173 and you should have it exactly.

The most important thing is that you make sure you don't over volt it.  Most of our stuff can only use 0 to 3.3v so your sensors must put out signals in this range or risk damaging your OSD/FC.

[HighAltitude]

Thanks Cliff -
GetFPV sells this unit, so I've emailed them for the info if they have it.
Failing that, I'll set up a test system by tethering one of my large electric fixed wing aircraft that can draw 40 or 50 A, connect the current sensor in series with my Watt's Up wattmeter between the battery and the ESC, and record the voltage on the sensor leads of the current sensor at several throttle settings/amp draws.  With the data, I can make a table and/or plot to check the linearity and calculate a current factor.  There's a pretty good description of how to add the sensor in the How To section of the Librepilot Manual, so it should go pretty well once I know the current factor. 
I'll be using Micro MinimOSD for display, so it'll probably take some experimentation with configuration to get the output I want.