RCOUT not all equal

I am trying to verify if my ESCs/motors are balanced. I did an ESC calibration and the copter seems to fly well.
ESC are ZTW Spider 30A opto. Motors are Sunnysky X3108S-720.
Checking the RCOU.Cx values from the latest 12 minute flight, mostly in AltHold mode (minimal changes of throttle) in relatively calm conditions, I get the following min/max/avg values:

RCOU.C1 125/224/186
RCOU.C2 125/244/195
RCOU.C3 125/244/203
RCOU.C4 125/244/200

What are the units for these values?
Any idea why the C1 max and average values would be about 15-20 less than the other 3 motors?

I think that is fine, they will never be 100% the same
the flight controller is making adjustments there to keep it stable
this is one of the things that is checked in the analyze logs. Acceptable limits are on the docs wiki
but your lowest to highest is is a 17 variance, that is pretty good

I also see that RCIN.C3 values are 982/1888/1401. Why such a big difference between rcin and rcout?
Does this mean the ESC calibration is off?

Looks like you’re using oneshot with your ESC’s. The timing period for oneshot is much shorter than standard PWM which is why you’re seeing such a big difference between RCIN and RCOUT.

Even if you weren’t using oneshot, APM Copter’s automatic hover throttle learning would mean that mid-stick on your transmitter (~1500) wouldn’t mean you would see 1500 output to your ESCs. Instead you would see the PWM value required to give enough thrust to maintain a hover which varies depending on your motors / props / payload etc.

Either way, this all looks very normal to me.

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That must be it. I just enabled oneshot125 (mot_pwm_type 2) after upgrading to v3.4.

Hence the min values of 125 . . . .

1.Check your frame, make sure the barycenter is at the right place.
2.Check KV number of your motors, make sure you are using the same. Same check to ESCs
3.Reset and re-program your ESCs

if you still face issue, exchange the motor and ESC with another arm’s