Gerry on Thu, 21 Jan 2021 23:45:18 -0500
typed in rec.crafts.metalworking the following:
On Thu, 21 Jan 2021 09:56:16 -0800, pyotr filipivich
wrote:
John Doe on Wed, 20 Jan 2021 17:09:48
-0000 (UTC) typed in rec.crafts.metalworking the following:
pyotr filipivich wrote:
Spehro Pefhany typed:
John Doe wrote:
https://www.amazon.com/gp/product/B00LJLV8AK
Was planning to buy one of their new calipers, but my 0.0 mm
resolution Mitutoyo still works fine.
I need to know the dimensions of a rod, to stop guessing whether it's
really 7.9 mm or actually 7.99 mm.
I would think such measuring devices jump to the next number when the
zero threshold is reached (going up) or crossed (going down). Will
see!
For just a few dollars (a small fraction of a stimulus check) mo
https://amzn.to/3iswLnc 0.001 mm / 50 microinch resolution.
One advantage to a non-digital micrometer - you can see if the rod is
almost 7.9mm or almost 8.0mm. (one of the reasons I like my dial
calipers.)
That depends on resolution, not whether it's analog or digital.
I think the reason I go crank on analogue is that in another life
I am dealing with the measurement of time and distance, before the
adoption of positional notation and decimal fractions. Back when
everything was Integer Math, fractions of a unit were expressed in
ratios of whole numbers. And if you were Roman, in base 12 (1/12th was
the 'unit' for most fractions. E.G. 'half' is 6/12th) Relatively
'simple' but some numbers didn't work out E.G.. twenty two to seven
(22/7) is the ratio of circumference to diameter. But Pi is not a
'rational number. And I'm digressing badly.
It also depends on if you need a specific size, or a "go-nogo"
evaluation. And the precision required or needed. When I was turning
drill cores (for oil rigs) spec was for 8" diameter with +.250 -
0.000 tolerance.So I set a non measuring caliper at 8 1/4 inches and
when the band got to where this fitted "it's done".
Some of the other processes were not just on the order of +/- 001
but holding +/- .0004 over the entire 16 feet. "And that's why those
guys got the big bucks" On manual machines, too. (powered by belts
from a water wheel! "Why when I was a boy, we didn't have these fancy
dial calipers, we had to use our fingers!" Blah, blah. Yes, factory
was old.)
Regardless of resolution, I can see if a measurement is closer to
N or N+/-[unit of resolution]. Is that 7.90001 or 7.99991?
IMHO, It doesn't matter the resolution or the number of decimal
places. I can interpolate +/- 1/2 the least significant digit. As
the saying goes "two plus two equals five for large values of two and
small values of five". I.E., 2.4 displays as Two, and 4.8 displays as
Five.
Of course, it helps if you can read an analog clock.
Also depends on resolution, given limited space for its display.
Yep. No sense putting a wrist watch on the wall - you can't see
the 'clock' let alone read it. (Heck, without my glasses, I can't see
the wall.)
With a digital display, only one dial is required, can't do that with
analog.
With a digital readout - you get to do the math. Be that inches,
millimeters, hours, seconds, degrees (arc) or degrees (temperature)
miles per hour, furlongs per fortnight, or parsecs in the old
Republic.
(On a side grumble, I've been looking to replace a garden thermometer.
Dial face, with two little arms which indicate high and low temps
since the last time they were reset. No longer made, but you can now
get a digital thermometer which you can press buttons until the min /
max temps are shown. Of course what was formerly accomplished at a
glance now requires an operator. And batteries. Which is another
"ought" I have against digital mics etc: batteries. Maybe if I used
them more often than once a year it would be different.)
It isn't like I am totally opposed to modern tech. I do
appreciate the digital temperature scanners at the club. I'd hate to
have to get a temperature reading the 'old fashioned way' with a
temperature sensing strip placed on my forehead. B-)
See: Lee Valley - Item AB803, Min-Max Thermometer
See also, shipping to the states. It is not worth (to me) the 30
bucks.
Yes, I know I'm whining. Part of being an old fart is asking why
"digital" or "computerized" is deemed to be an improvement on what
works? How precise do the measurements _need_ to be? Like I've said,
I'm retired - most of frequently the answer the question "What time is
it?" is "Tuesday, mid morning." Same applies to measurements. Some
times I do need to know the size of 'this' to within a thou. Sometimes
.... ten feet "plus or minus a quart." will suffice.
E.G., Do I really need to know that it is precisely 38.567 degrees
Fahrenheit in that corner of the yard when what I want to know is
whether it got below freezing?
Do I really need to know if this Ethernet cable is precisely 9
feet 11 and three quarters inches, if I just need to know "Will a ten
foot cable reach from here to there?" (And yes there have been
occasions when the cable is just a smidge too short, so something will
have to be moved.)
--
pyotr filipivich
"With Age comes Wisdom. Although far too often, Age travels alone."