Experimental Measurement System

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Sep 16, 2013, 05:40 PM
rgsparber

Experimental Measurement System

I wanted an excuse to learn how to program an Arduino (computer system on a chip) so decided to see if I could improve the performance of a $10 Harbor Freight caliper. The results are shown in these two videos. The first shows the basic functionality of automatic hold, automatic minimum detection, and automatic maximum detection. It also shows half of the measured value at all times. This can be handy if you are working on a lathe and you measure diameter yet the cutter in-feed is marked for radius.

The second video shows how gage blocks can be used to build an error correction table that improves the accuracy of the caliper.

One possible future feature that would be very easy to add would be a go/no-go test. The display screen would show "below", "OK", or "above" and not bother the minimally trained user with an actual number.

I would be interested is hearing other suggestions for new features.

Thanks,

Rick

The basic system:

Digital Caliper Measurement System (first of two videos) - YouTube

Improved accuracy using gage blocks:

Digital Caliper Measurement system (second of two videos) - YouTube

For full details, please see

http://rick.sparber.org/CBOO.pdf
Sep 17, 2013, 08:38 AM
kbalch

Hi Rick,

Looks great, as always. Do you have a page on your site for this project, or just the YouTube videos? For the sake of consistency, I'd prefer to have all of your projects linked back to your own site.

If not, no problem. I can always link to this forum thread.

Ken
Sep 17, 2013, 08:48 AM
rgsparber

Ken,

I will be writing this up soon but wanted to test the waters with the videos first. I was hoping to gather a few suggestions for new features before finishing the programming and starting the docs.

Rick
Sep 17, 2013, 10:49 AM
kbalch

Rick,

Got it. Just post in this thread again when you're ready and I'll add it to the database.

For a work-in-progress, it looks quite usable. I'm looking forward to seeing the finished version.

Ken
Sep 19, 2013, 05:45 AM
rgsparber

Quote:

Originally Posted by kbalch

Hi Rick,

Looks great, as always. Do you have a page on your site for this project, or just the YouTube videos? For the sake of consistency, I'd prefer to have all of your projects linked back to your own site.

If not, no problem. I can always link to this forum thread.

Ken

Here you are:

http://rick.sparber.org/CBOO.pdf
Sep 19, 2013, 11:53 AM
kbalch

Thanks Rick! I've added your Experimental Measurement System to our Measuring and Marking category, as well as to your builder page: Rick Sparber's Homemade Tools. Your receipt:

<div id="blocks"> <div class="block b1 pngfix"> <div class="bimg"> <div> <a href="/experimental-measurement-system"><img src="/uploads/61256/experimental-measurement-system.jpeg" alt="Experimental Measurement System" /></a> </div> </div> <div class="head pngfix"></div> <div class="left pngfix"></div> <div class="right pngfix"></div> <div class="blockover b1 pngfix"> <div class="title"> <a href="/experimental-measurement-system">Experimental Measurement System</a> <span> by <a href="/builder/Rick+Sparber">Rick Sparber</a></span> </div> <div class="tags"> tags: <a href="/tag/caliper">caliper</a>, <a href="/tag/arduino">Arduino</a>, <a href="/tag/software">software</a> </div> </div> </div> </div>
Sep 20, 2013, 09:05 AM
rdhem2

Sorry but I am confused. You calibrate the caliper then measure a .060" block. Display shows .059".

What are we to think?

Caliper is not accurate.

Block is actually .059".

Sorry if I am thick between the ears.
Sep 27, 2013, 02:32 AM
Workshopshed

I am following this with interest. I've been working on a rotary sensor and calibration is also a challenge.
Sep 27, 2013, 04:26 AM
rgsparber

Quote:

Originally Posted by rdhem2

Sorry but I am confused. You calibrate the caliper then measure a .060" block. Display shows .059".

What are we to think?

Caliper is not accurate.

Block is actually .059".

Sorry if I am thick between the ears.

The block is accurate at .0600 and the caliper is reading a thou low. The computer corrects the error and puts the result on its own display as .0600. Could you be looking at the wrong display?

Rick
Mar 13, 2015, 12:01 PM
kbalch

This thread has been moved to the Must Read subforum. Congrats (and thanks) to Rick for making such a valuable contribution!
Oct 14, 2017, 06:51 PM
pfredX1

I tried to improve the performance of those HF calipers by taking them apart, deburring them, and cleaning the grinding sludge out of them. The results of that were mixed.
Oct 14, 2017, 08:53 PM
rgsparber

Quote:

Originally Posted by pfredX1

I tried to improve the performance of those HF calipers by taking them apart, deburring them, and cleaning the grinding sludge out of them. The results of that were mixed.

I have found a wide variation in HF calipers probably due to a variety of suppliers. I try them out in the store and if rough, just move on to the next box. The best ones are great. The rest are not worth buying. Once I have a mechanically sound caliper, this does not mean it is accurate. But as long as the error doesn't change, my system can cancel it.

Rick
Oct 19, 2017, 10:58 PM
Paul Alciatore

Rick,

That looks like a wonderful idea. I am planning to install some scales and perhaps one caliper on my mill for a shop made DRO and I will want to bring the readings from those scales and caliper to a central display so I am very interested in the code used to pick up the caliper's readings. I will be watching this thread so please do publish more on this.
Oct 19, 2017, 11:06 PM
Paul Alciatore

I have several of the Chinese import calipers and have found that the biggest problem with them is the fit between the beam/scale and the sliding head. There are a couple of small screws that are intended to allow you to adjust the fit and clearance, but that adjustment is difficult. I suspect that the beam/scale is not ground to a uniform width along all of it's length so you must have some slop in places so that other places will allow movement. Probably the biggest improvement you could make to them would be to carefully spot the beam/scale and then bring down the high spots. Of course, you would need to keep it straight during this procedure. This is probably the first, big difference between the imports and the quality brands.

Quote:

Originally Posted by pfredX1

I tried to improve the performance of those HF calipers by taking them apart, deburring them, and cleaning the grinding sludge out of them. The results of that were mixed.
Dec 5, 2019, 12:58 PM
Carnel

Hi Rick, an eye opener for me. Never had the idea of connecting my caliper to my scope. Tanks!
Do you know these sites:
Chinese Scales
https://www.instructables.com/id/Rea...n-Arduino-USB/

Cheers,
Harry
Dec 5, 2019, 05:38 PM
rgsparber

Quote:

Originally Posted by Carnel

Hi Rick, an eye opener for me. Never had the idea of connecting my caliper to my scope. Tanks!
Do you know these sites:
Chinese Scales
https://www.instructables.com/id/Rea...n-Arduino-USB/

Cheers,
Harry

I am familiar with the Shumatech site. The instructable article was new to me. I was not comfortable with how they interfaced the Arduino with the caliper. They do say it is a bit of a hack. IMHO, the hard part is figuring out which data format you have. After that, the driver software is not too bad.

Rick