I don’t know if it’s completely analogous, but in medicine, when a patient has a particular set of symptoms, there are usually a list of diagnoses that can be generated from most likely, to least common.
As a hobbyist using a timegrapher, I have a general sense when looking at rate, amplitude, and beat error, in terms of what’s in the range of acceptable, and what’s not.
What I don’t have a grasp on, is for every one of these parameters, when each is either out of range high, or out of range low, what it
tends to indicate could be the cause of the problem in the watch. Can any of our esteemed watchmakers or tinkerers fill in the blanks? To keep things simple, we can limit to dial up, or maybe dial up, crown down and crown left, at full wind. And whatever else I forget or didn’t know, that figures into the equation. I realize I am probably distilling out a complex set of variables into something simple, but nonetheless:
Rate:
1) high:
2) low:
Amplitude:
1) high:
2) low:
Beat Error:
1) high:
2) low:
It's tough to give a good concise answer to any of this. Some my immediate thoughts were to ask more questions, because they are very vague and the question really has several layers to it. At the same time some of these could have many different causes.
So for example the rates - high or low rates could just be a matter of regulation, which is simple to resolve. But no watchmaker I know would regulate based on rate alone, without ensuring that the watch is performing well in other ways, such as the balance amplitudes. If the rates are fast and the remainder is good, then it's likely just a regulation issue. If the balance amplitudes are all low, then rates are not the problem - the watch needs servicing or repair.
Another example is balance amplitudes. Too high is typically a barrel issue, so too much braking grease, or an incorrect mainspring. However in some instances it may be related to the adjustment of the pallet fork jewels, or even wear on the escape wheel.
For low amplitude, it could be so many things that it would be difficult to list them all. It could be something as simple as a screw being installed in the wrong location causing drag on the barrel (I've actually seen that one personally, so it's not something I'm making up), or it could be dried oils, debris in the movement, too weak of a mainspring, etc.
Low amplitude may be low in all positions, or low in just one position. What I've described just previous is for low amplitude in all positions. But if there's say good amplitude dial down, but much lower dial up (common) I'll be looking for wear on the balance staff and the cap jewel when I take the watch apart. So certain details may lead you to look more closely at a specific area, but the diagnosis would only be confirmed when you find the physical thing that you are looking for - if that makes sense.
Here's a link I was able to find to the Witschi training course - it's a pdf that explains some basics of how these machines work, and gives some troubleshooting for basic things...
Witschi+Training+Course.pdf (squarespace.com)
Note that the remedies offered don't give you a lot of detail sometimes, like when they say "overhaul" the watch.
From a very practical stance for a watchmaker, when I get a watch in I perform some pre-service testing, to see what the timing is like, if there are any functional issues with winding, setting, when the date changes, how well the chronograph works, etc.. But in the end I know I'm taking it apart anyway, so really the detailed diagnosis comes when the watch is coming apart, or after it's apart, cleaned, and I can inspect all the parts.
If I have done my job properly when doing the actual work, then there won't be any diagnosis when the movement has been serviced and is running, because I'll have resolved all those issues in the watch already.
Hope this helps.
Cheers, Al