@KyleG
I wanted to see if my lathe cross feed magnetic DRO was accurate. It is suppose to have 1 micron resolution, but what about the accuracy? So I purchased one of the cheaper digital display dial indicator. 0.001mm (1 micron) resolution with a 25mm stroke. I paid about $45 for it and connected the digital gauge to the lathe and compared its reading to the DRO.. But this left me with even more questions. It seems to be pretty good at measuring small differences if you are sliding it along a surface or even if you pull the plunger back and set it down on a surface repeatedly, but it turns out to be really hard to determine accuracy over the full stroke.
What do you used for a reference if you do not have anything that has been certified? I have a number of micrometers, but nothing that was certified in the last 10 years if ever. I even built a fixture to hold the digital dial indicator opposite a 1 micron resolution mechanical micrometer head and let the head push the dial indicator .... taking a reading from both and plotting the error. I found that even the cheap $45 unit appears to be accurate over the 25mm stroke to withing ~15 microns (~0.0005"). I think it may have even been better at the beginning, but I may have clamped it too hard or abused it before I started the measurement... causing some friction for the plunger.
More recently I purchased a slightly more expensive version of one of these from Clockwise. Amazon: "Clockwise Tools DITR-0105 Electronic Digital Dial Indicator Gage Gauge Inch/Metric Conversion 0-1 Inch/25.4 mm 0.00005 Inch/0.001mm Resolution with Back Lug Auto Off" There is also one with a probe tip set for just a bit more.
https://www.amazon.com/Clockwise-Tools-DITR-0105-Indicator-Resolution/dp/B08H4943GZ
or their store
https://www.amazon.com/stores/page/...b663-04d6-40a7-a4e3-9272a8cb582a&ref_=ast_bln
I paid about $63 (no probe tip set) because they promised to send an error curve, which they did. It is much better than the first as It is more robust, the parts inside are all metal, machined, thicker, etc.... and the plunger moves extremely smooth with no obvious friction. I also purchased the RS232 cable: "Clockwise Tools DTCR-01 RS232 Digital Indicator Data Transfer Cable" It has a small box with push button switch inline with the connection to the dial indicator and the USB port on my computer. Push the button and the data appears in Excel or Word and drops the cursor down one line to capture the next data point. Very slick and handy. It also has an external trigger so that you could automate getting the data with a computer or you could implement a foot switch. The cable costs about $40.
This DITR-0105 digital indicator has a 1 micron resolution and appears to function that way pretty well. Performing an entire 25mm stroke the accuracy seems to be ~ 7 micron worst case. I think this is pretty darn good for only $63. The Amazon seller even sent me a message asking if I was dissatisfied or had any problems. If so I was to simply say so and they would replace it. All of the metal parts in it are thicker and stronger and appear to be machine worked, rather than just cast or made from plastic. The inside guide is brass not plastic. The probe shoulder used for mounting is thicker and larger in diameter so is also better to clamp to. It uses a 3V coin Li-Ion battery (CR2032 I think) where as the cheaper unit uses a 1.5v button cell so it probably last longer and should be more stable. I have run them both for hours and the batteries seem fine.
By the way, while all of these digital micrometers I have looked up have an Off/On button this only turns off the display. So even if the display is off, and you move the probe the micrometer is still functioning to take data! The only way to truly turn off the power is to remove the battery. If you are going to store these things and not use them I would recommend removing the battery. When I got the devices from the sellers they both had batteries in them. But the batteries needed to be replaced. The $63 unit came with a spare battery 3V cell.
Anyway, I am going to purchase a couple more of these Clockwise units. There are a lot of these things being sold, but this Clockwise version appears to be the best of them unless you may want to spend a few hundred dollars. While a lot of the others say that their devices are cable ready they do not sell the cables..... Clockwise also seems to be one of the few sellers that sells an RS232 cable.
PS. There is also a Clockwise unit that is slightly cheaper model number which seems to end in "N", i.e. DITR-0105N which do not have the cable interface. There are also versions that only have 1/2" stroke or which only have 0.01mm resolution. The prices are cheaper.
If I ever finish with, and am happy with, my calibration procedure of these devices vs my micrometer heads or the lathe DRO I will post the results. However, I must admit that when one gets down to trying to measure distances to only a few microns a lot can go wrong in the process.
Dave L.