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current sensor calibration
#1
Hey all,

I'm trying to calibrate the current sensor, but my power meter is doing a strange readings  Cry Cry Cry Cry
I did a short video to show you what's going on:


Anyone know whats going on here and how to solve this?  Thinking

Thank you and sorry if im posting this in the wrong section.
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#2
Big Grin

I'd say your meter is broken!

The safest and easiest way to calibrate your quad's current sensor is by comparing the reported mA/h used with what your charger puts back in. Start with a fully charged battery, fly for what should be at least half to 3/4 of the pack's capacity, note how many mA/h the flight controller says you have used and then re-charge the battery in charge mode, not balance charge mode. Note how much the charger puts back into the battery.

Then, take the reported mA/h figure, the replaced mA/h figure and the setting of the current meter scale on the flight controller and apply the following calculation:

amperage_meter_scale = old_amperage_meter_scale * (reported_draw_mAh / charging_data_mAh)

Repeat the test. You may need to recalculate a second or third time to get it as accurate as you can.
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#3
That was my first thought... broken meter.
I bought a good quality clamp meter, and I have the same strange readings.

I would like to know what is causing these readings Thinking Thinking
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#4
Please, there's no need to write your messages in such a huge font. My reading glasses are working perfectly well! Wink

If these readings are for real, you are experiencing an intermittent short circuit and my first suspicion would be that the screws you have used to mount your motors are too long and are causing the motor windings to short to the frame. Alternatively, something else on your build is shorting out. It would seem that the small amount of vibration that the running motors cause is sufficient to provoke whatever is causing the short.

Some clear pictures of what you have built and how you have put it together would help, as would a description of what quad you have built and with what hardware. Your video only shows a symptom and all I can do is guess at the cause.

Is this the first quad you have built? How experienced are you at building electronics?
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#5
Hi unseen,  Big Grin
Sorry for the huge font, i was not screaming or something like that, my english is not very good and I made a copy paste from google translate and the font was that size, sorry for that.
Also sorry for the lack of info, in this reply I will try to put everything as explicit as possible.

My setup:
Flight controller: Genuine Omnibus Flip 32 f4 V3 Pro http://www.readytoflyquads.com/flip-32-f...bus-v2-pro
PDB: Matek PDB-XT60 W/ BEC 5V & 12V https://www.banggood.com/pt/Matek-System...rehouse=CN
Esc's: Racerstars 20A 4in1 https://www.banggood.com/pt/Racerstar-RS...rehouse=CN
Motors: DYS Fire 2600 KV http://store.rotorriot.com/dys-fire-2206-2600kv-motor/
FPV Cam: HS1177 http://store.rotorriot.com/xat-600m-hs1177-fpv-camera/
VTX: Eachine ATX03 mini https://www.banggood.com/pt/Eachine-ATX0...rehouse=CN
Receiver: Frsky x4r sb https://www.banggood.com/pt/FrSky-X4R-SB...rehouse=CN

This is the third quad i built, but is the first with a current sensor.

This is how everything is connected (amazing paint skills):
[Image: b8tik1.jpg]
Things I've tried to figure out the problem:
I searched with the multimeter for short circuits and did not find anything.
I turned off the fpv system but nothing changed in the readings.
I put hot glue on all the welds


My quad is flying very well, without oscillations, nothing gets hot.... i dont really undrstand what's going on  Thinking Thinking
If you need more info or pics just tell me.
Hope you can help me with this info  Smile
[Image: PlLnz]
Reply
#6
Ahh... a PDB and an Omnibus with a current sensor and a 4-in-1 ESC eh?

I'm not 100% certain of how you've wired things up, but this is a tricky one to get right sometimes. As the quad flies well and doesn't fall out of the sky, it does tend to minimise the chances of a short, but I'm at a loss to understand why an external device would show huge peaks in current draw without them actually happening.

What your Omnibus is showing in your video seems about right for the motors spinning at low speed, so let's assume that your current sensor on the flight controller is wired correctly and is working properly.

When the current draw on your external meter rises and falls, the voltage remains constant. If you really were suddenly drawing 48A from your battery, the voltage would certainly drop. There is no way it would still remain stable at 15.53V unless you are running the quad from a high capacity regulated power supply instead of a battery.

Are you using a battery during that test?
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#7
Yes, im using a battery.
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#8
OK. Well that kills off that theory.

You say you verified what your power meter was showing with a clamp meter? If so, then I'm completely mystified.
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#9
Well i give up......
I dismounted the quad, made new welds, insulsted everything with hot glue, and still have very weird readings on power meter and clamp meter.
Huh Huh I dont know what to do anymore  Huh Huh

Anyway thank you for your help.
If anyone reads this in the future and knows what's going on please reply
[-] The following 1 user Likes Nefer's post:
  • unseen
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#10
Put it this way:

If the quad flies just fine, calibrate the current sensor using the battery charge method that I described and leave the strange behaviour you are seeing from your power meter as a curiosity.

There's no point worrying about it if everything else is OK and you'll get accurate calibration results using the charge out/charge in calculation.
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#11
I Will do that. 
Once again thank you  Thumbs Up
[-] The following 1 user Likes Nefer's post:
  • unseen
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