Where to learn how to better use diagnostics graphing?

It is assumed that you have already carefully read the instructions in the DIAGNOSTIC section; therefore, there is no need to repeat here what has already been explained in the instructions.

As you will have seen, there are many loggable parameters (currently 55 different parameters, but more are often added with new releases). Although brief, the descriptions are sufficient to explain what the various parameters represent.

To get a clear and complete idea of what the graphs for each parameter can indicate, you need to have a good multidisciplinary knowledge of electronics, mechanics and how RC helicopters work. It is therefore not possible to explain everything here, as it would require writing a manual of several hundred pages containing all the necessary basic concepts.

The diagnostic graphs are used to:
- Optimise the model setup
- Diagnose the health of the model over time
- Help identify the causes of any problems.

There are also many other parameters used for firmware development that are not made available to end users because they are useless without a thorough understanding of how the firmware works.

For these reasons, when we are asked for remote assistance, it is essential that you send us at least one recorded log file, the event file and the flight controller configuration file. Otherwise, without being able to see the model in front of us, with the transmitter turned on and the flight controller connected to the PC, it is impossible for us to “see” how the model behaves.
We have written about this here:
https://www.msh-electronics.com/forum/support/when-you-ask-for-support

and also here:
https://www.msh-electronics.com/faq/#Q01

Despite this, 90% of the support requests we receive still do not have any of these files attached, which we have to ask for each time before we can start responding, wasting time and delaying our responses to users, given the possible delays caused by different time zones, which can cause responses to be delayed by a full (working) day.

To understand the meaning of the graphs of the various parameters, all you need is logic, a little common sense and to have seen at least once in your life how an oscilloscope works.

As we cannot explain in detail here the possible meanings of the graphs for each of the 55 parameters, here are just a few simple examples of some curves:

Servo Voltage (see also SatVoltage): This is the voltage of the Servo Bus that powers the receiver, flight controller and servos.
The curve should be as straight and “clean” as possible. If there are significant voltage drops, it means that the BEC (or the battery in combustion engine models) is not supplying enough current or that some device (usually servos that are under load and stress) is drawing more current than it should. If, on the other hand, the voltage is straight but dirty, it means that the contact resistance of the connectors and the voltage drops in the cables are excessive. You need to check that the secondary outputs of the BEC are also connected, that you are using extension cables with sufficiently high cable cross-sections and that the connectors have gold-plated contacts with low contact resistance (the connectors on our flight controllers are already gold-plated and, although more expensive than tin-plated contacts, they do not cause high contact resistance).
It may be necessary to add an electrolytic filter capacitor which, in addition to filtering noise, also acts as an “energy reservoir” to compensate for high current peaks, even if they are short-lived.
All linkages must be disconnected from the servo uniballs and checked one by one to ensure that there is no friction or strain when moving by hands the model's control commands. If this is not the case, clean, unblock, lubricate and grease the parts.
If, on the other hand, you are checking the “ESC Battery Voltage” parameter and there are significant voltage drops, this means that you are using a battery with a “C” value that is too low for the ESC and motor requirements, or the cables are too long and thin, or you are using a connector with a maximum current value that is too low and of poor quality (non-gold-plated but brass contacts). As a result, the ESC may shut down due to the ESC's LVC protection.

RPM: here too, the curve should be as straight as possible (perfectly straight is impossible; a variation of 5% is acceptable) so that the torque generated by the main rotor, which must be compensated by the tail rotor, is as constant as possible, allowing for even better tail stabilisation. Furthermore, since the maximum rotation speed of the model depends on the speed of the blades, having stable RPM means having consistent rotation speeds on the three axes of the model with respect to the commands given by the pilot, making control much easier.
If there are constant frequency oscillations in the RPM graph, it means that the ESC governor and the flight control unit governor are active at the same time and are in conflict with each other because while one governor increases the RPM, the other governor, which sees the increase, tries to reduce it, causing this sawtooth-shaped indentation of varying width on the RPM curve.
If there are occasional short-lived constant increases in the form of square waves in the RPM curve, it means that something is slipping, causing the motor to suddenly lose load (for example, the one-way bearing, the pinion on the motor shaft, the motor shaft on the motor case or the crown on the main shaft may be slipping).
By comparing the RPM curve with the other collective and cyclic pitch curves, you can check whether the relative pre-compensations of the proactive governor need to be increased or decreased.

RxFrameRate: allows you to check that the signal received by the receiver and sent to the flight controller is at a constant repetition frequency without data loss and is always valid. If the Frame Rate curve indicates increases in the time between one valid data frame and the next, it will be necessary to investigate further to understand whether the receiver is powered by a clean and constant voltage (see above ‘Servo Voltage’), whether the antennas are visible and not shielded by the carbon frame, which is conductive and acts as a shield to radio signals, or shielded by other metal parts, or whether the receiver is disturbed by power signals passing too close to the receiver and/or antennas (battery cables, motor cables, ESC cables, which can emit strong interference).
In case of problems with the received signal, you can ‘dig deeper’ with the other QOS (Quality Of Signal) parameters such as Fades, Frame loss, and Holds (see explanations in the answer to question 29 in the FAQ section).

In general, when there are problems with one of the five output signals from the flight controller (XxxxxOut), you can check whether the same problems are already present in the corresponding signals coming from the receiver and going into the flight controller (RxXxxxxxx).

Other parameters are obvious, such as temperatures, to understand if there is a short circuit (CPU temperature rises) or problems with the ESC, which is undersized or poorly adjusted and heats up more than normal, or if it exceeds the maximum limits and is about to melt (in which case the signal that is also transmitted to the transmitter via telemetry and an alert would be triggered, requiring the motor to be stopped immediately and the aircraft to descend to the ground by autorotation).

These are just the most obvious and simple things, although they could be explored further. It is pointless to go any further and explore them in greater depth because, as already explained, it would take too long.