I am new to ArduCopter APM 2.5 and I am struggling to get it stable enough to fly. I have issues with spontaneous flipping and losing ESC calibration. What I discuss below may (or may NOT) be an issue, but at least I can reproduce the issue and measure it with some certainty.
Setup: + config, no props, quad and board leveled , ESCs calibrated, 11.4 VDC input from regulated power supply, throttle up one click above off, no hands on Tx.
Observed: Front and Rear motors run 9200 (+/- 400) RPM. Right and Left motors run 6300 (+/- 100) RPM. There is some small drift over a few seconds. The +/- drift occurs over tens of seconds. Randomly about every 30 to 50 seconds the RPM will blip ( I cannot tell if it blips up or down) and return to previous state. This has been observed several times over periods of ten to twenty minutes. There is no overheating. There are no loose connections. Voltage and current are stable. I used both a laser strobe and a strobotach for RPM measurements and they agree within about 100 RPM, depending on the severity of the drift.
Here is a screen shot of the pulses going into the ESCs. The pulses are steady and show no noticeable difference in length over time.
Here is a shot using the strobotach. Neither silver lines should not be blurred. I did not have enough flash strength to capture all discs at once and get a decent photo.
Question: Is this an issue or not? I would expect all motors to run at the same RPM.
Any and all comments are welcome.