- Joined
- Feb 28, 2019
- Messages
- 499
TLDR: is this a good choice (below) for the finest resolution indicator that I'll probably own?
--------------------------
Looking to add a high resolution test indicator to my collection (excuse is to measure run out on a high speed spindle).
Specs in catalogs are a little confusing base on my expected definitions.
Graduation -
This is easy, the space between the marks on the dial, (mostly) has nothing to do with accuracy or resolution only how hard or easy it is to read or determine values between the marks.
Accuracy -
How close it comes to the actual TRUE measurement as defined by NIST (or whatever it is) (see also calibration and certification). Most hobbyists don't need super-accurate as we are not trying to make stuff to share with someone else and if our .001 is really .00091 it doesn't matter.
Resolution -
What's smallest value that can be observed, like with a telescope (aperture determines this) the mechanics of test indicator limit the smallest distance it can detect.
I'm looking at this indicator:
The graduation is half of the accuracy. I'd expect the resolution to be less than the graduation maybe 0.00001?
Meaning, you can detect differences less than 0.00005 but if you are trying to measure a difference you can't be sure that it's better than 0.0001
So if I was to put this on a spindle and rotate it, I could observe the needle swinging back and forth. If it stays between to marks, I still can't say for sure that the run out is less than 0.0001 (accuracy) despite the fact that two marks indicate a travel of 0.00005? Looking at others it seems that accuracy is often a bigger value (2X) than the graduation.
[I took a break and did some more research before posting]
I got the manufacturers part number from the MSC catalog and looked up what the manufacturer actually has for specs and poked around a bit....
So clearly, MSC has mis-labeled the manufacturers info. MFG has RESOLUTION as 0.00005
They don't have GRADUATION - but the picture clearly shows that the graduation is 0.0001
MSC has flipped them around.
Moral of the story is don't trust the catalog info?
--------------------------
Looking to add a high resolution test indicator to my collection (excuse is to measure run out on a high speed spindle).
Specs in catalogs are a little confusing base on my expected definitions.
Graduation -
This is easy, the space between the marks on the dial, (mostly) has nothing to do with accuracy or resolution only how hard or easy it is to read or determine values between the marks.
Accuracy -
How close it comes to the actual TRUE measurement as defined by NIST (or whatever it is) (see also calibration and certification). Most hobbyists don't need super-accurate as we are not trying to make stuff to share with someone else and if our .001 is really .00091 it doesn't matter.
Resolution -
What's smallest value that can be observed, like with a telescope (aperture determines this) the mechanics of test indicator limit the smallest distance it can detect.
I'm looking at this indicator:
The graduation is half of the accuracy. I'd expect the resolution to be less than the graduation maybe 0.00001?
Meaning, you can detect differences less than 0.00005 but if you are trying to measure a difference you can't be sure that it's better than 0.0001
So if I was to put this on a spindle and rotate it, I could observe the needle swinging back and forth. If it stays between to marks, I still can't say for sure that the run out is less than 0.0001 (accuracy) despite the fact that two marks indicate a travel of 0.00005? Looking at others it seems that accuracy is often a bigger value (2X) than the graduation.
[I took a break and did some more research before posting]
I got the manufacturers part number from the MSC catalog and looked up what the manufacturer actually has for specs and poked around a bit....
So clearly, MSC has mis-labeled the manufacturers info. MFG has RESOLUTION as 0.00005
They don't have GRADUATION - but the picture clearly shows that the graduation is 0.0001
MSC has flipped them around.
Moral of the story is don't trust the catalog info?
