Gallery, Projects and General > How do I??

DRO calibration

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Hmmmm (number 4?) I think my parallels are 6" long......

Wait, 123 blocks..... two = 6"......... put together, mike, and go.

Back to square 1....  :wack:

John Rudd:
I seem to be missing something here…..
My  understanding of calibration is to have a zero and span adjustment and possibly a linearity …..( I come from an instrumentation background….think pressure gauges et al)

So for a dro, mine for example doesn’t afford such adjustments…’s a standard dro readout and glass scales…

So could you elaborate on the process for calibrating yours Steve please?

Okay so here's the tentative procedure:

1) clamp a bar across the table.
2) indicate it square in the y direction
3) lay two 123 blocks together and check their length with micrometer
4) place them against the bar
5) bring the indicator up to blocks
6) zero the indicator, DRO, (and out of curiosity) the mill dials
7) remove blocks and crank to the stop
8) check readings
9) adjust : (DRO reading / Actual length) X Present Lines Per Inch setting = New setting
10) repeat 4 thru 8 as a check

John, the above wasn't an answer to you -- just typed while you posted.

My scales are inexpensive capacitative scales of unknown specs, re-purposed into a DIY bluetooth DRO unit. The software for that does allow calibration (it is designed to use many different kinds of scales with different lines per inch resolution) So yes it is possible to calibrate initially to match the scales.

Yes most commercial scales are made to a high standard, so you can depend on the mfr's statement of resolution. But in my case that info is not available. So in a sense I'm reverse engineering.

And apparently these scales have a non-standard (meaning non-intuitive metric or inch) resolution of approximately 2560 lines per inch. I wanted to see just how close I could get by actual measurement to the reality of these scales, as installed.

So well, this isn't what you would normally do, but it is an interesting problem, and will help us (meaning me) learn a little more in the process.


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