This seems to be evolving into an apples and oranges discussion.
I think I totally understand and fully agree what DaveBen is trying to say about the fundamental purpose of a good guage: to report accurate and actual measurements as they are dynamically changing in real time.
But I still don't think I understand how a "hard wired" or "analogue" guage is the only way, or the best way, to get real time accurate measurements.
The individual guages I installed over 10 years ago are not networked into a central processor like the Performax. I guess they are individual "old fashioned" guages. But I'm not sure that means they are hard wired, or analogue, either... and I'm the one who wired them!
We can break down what DaveBen is trying to get across about a good gauge into two steps:
1. Measure accurately. (in real time)
2. Tell us the measurement. (in real time)
Does it matter how those two steps get done, just so long as they get done?
On the three guages I installed, it appeared to me as though Step 1 was done by the "Probe / Sending Unit" which was attached directly (hard wired?) to the object being measured. Amd Step 2 was done by the "Guage Face" ...as that'd be the only way I could see the results from Step 1.
In looking at and handling my Sending Unit / Probes, it appeared to me that these devices converted a measurement of heat into a low voltage signal (Step 1), and then sent that low voltage signal electrically to the Guage Face to be processed and converted into needle movement so that I could see it (Step 2).
It did NOT appear to me as if they conducted all the heat they measured along that wire. The wire wasn't thick enough to handle that kind of heat, nor was it protective enough to keep the heat from dissapating somewhat before it reached the guage face.
So it seems to me that even with individual guages, there is some "signal processing" going on. The sending unit is processing measurements into an electronic value that the guage face module can then process and convert into needle movement that I can read. Since electricity travels at the speed of light, this processing essentially occurs in real time.
Instead of each guage head having it's own individual RE-interpretor of electrical signals that themselves are only the already converted signals from measurements taken by the sending units... why not send the signals from the sending units to a more capable central processor? What difference might it make if the processing to do Step 2 (telling me) takes place inside the guage head itself, or inside this central processor? It doesn't seem that either one gets as hot as the thing measured... since either one is still only receiving the electrical signals from sending units that took the heat and already converted the measurements into those signals.
Would the accuracy of Step 1 be effected by how Step 2 gets done? It doesn't seem so, if the goal of the processing of Step 2 is to report Step 1.
In the case of Ford's transmission temperature guage, that was NOT the goal, according to Mark Kovalsky, a popular car and truck forum citizen and forum moderator on some diesel truck sites whose previous career included a long tenure at Ford Motor Company working on the very automatic transmission (5R110W) that Ford's guage was developed to measure. Mark reported that this guage was intentionally "damped". In otherwords, the Step 2 function was made to respond differently (slower, and averaged, on purpose) than the real time reporting we all here agree that we prefer.
So the inaccuracy of Ford's transmission guage isn't the result of a centrally processed guage... it is the result of Ford's engineering design choice. From this example, it doesn't make sense to throw the baby out with the bath water and conclude that a more capable central processor is not as accurate as a similar type of processor located inside an individual guage head.
Thinking about automotive guages from 90+ years gone by, I was reminded of when I had to take the dashboard apart of my previous Ford pick up... a 1979. The design of that truck's guage cluster is almost 40 years old now, given the '73-'79 F-Series was designed prior to 1972. I had Ford's full gauge package in my Lariat F-250 Ranger XLT. Instead of idiot lights in all the little rectangles, there were factory guages. With the intrument cluster removed, I found that all of the guages were backed by a printed circuit piece of plastic, similar to a flexible motherboard (only the circuit traces were a Neandertholic 1/16" wide!). Even back then!