Extended-length digital vernier scale - Page 1
Forum section: electronics / general

author: MarkMLl
author_rank: Frequent Contributor
timestamp: August 31, 2022, 07:21:55 pm
content: I posted this link as a StackExchange answer earlier in the day since I thought it was likely to help somebody, but after being criticised for procedural reasons deleted it to avoid further grief. However I think it's a cool enough hack that it's worth sharing while I've still got the reference to hand:https://hackaday.com/2021/08/05/custom-caliper-tracks-for-when-youre-going-the-distance/The gist is that somebody's discovered that with a bit of clever PCB fabrication it's possible to get cheap vernier calipers to operate over substantially more than the typical 150mm (6") they're intended for, and since many of these can be easily modified to emit serial data they can be used anywhere that a length can usefully be read electronically: machine tool readouts and so on.MarkMLl

author: mendip_discovery
author_rank: Super Contributor
timestamp: August 31, 2022, 07:37:46 pm
content: Well you can buy 1000mm vernier calipers easy enough. Better still buy a linear encoder from Mitutoyo and get advantage of a glass scale and a resolution of 0.0001mm vs 0.01mm. A firm in the uk will also sell you vernier caliper type scale in common lengths for not a lot.So this seems to have come up with a inaccurate and complicated solution to somthing easily fixable.

author: thm_w
author_rank: Super Contributor
timestamp: August 31, 2022, 10:14:10 pm
content: Cool.igaging and others sell these as a kit for a reasonable price up to about 24". But I could see a situation where you wanted a very very long measurement axis and had to do custom.You can also get a mag sensor and up to 50m of tape:https://www.aliexpress.com/item/3256801612324604.htmlThis is the DRO adapter the person is using:https://www.touchdro.com/

author: Warpspeed
author_rank: Contributor
timestamp: August 31, 2022, 11:15:19 pm
content: These cheap calipers sometimes do have an external serial port. The problem is there is no standard communications protocol, even if you can source a suitable plug. Data speed, number of bits, MSB or LSB first is not even established. Its all a real can of worms.I suppose anything is possible, but its hardly worth the effort.Linear incremental quadrature encoders (for machine tools) are readily available for any length up to several feet.

author: thm_w
author_rank: Super Contributor
timestamp: September 01, 2022, 10:18:20 pm
content: Quote from: Warpspeed on August 31, 2022, 11:15:19 pmSee the link above where most of the common protocols are documented. Easy enough to solder the plug or some use USB connectors.But effort wise, yes this is hobbyist area of interest, anything other than that you just buy the industrial grade parts.

author: mzzj
author_rank: Super Contributor
timestamp: September 03, 2022, 07:43:23 pm
content: This would have been nice option 15 years ago. Nowadays you can get 1000mm linear glass scale with less than 50usd/eur

author: Warpspeed
author_rank: Contributor
timestamp: September 03, 2022, 11:55:34 pm
content: These machine tool sensors also use incremental quadrature encoding, which just means a simple hardware up/down counter will work, or some simple home brew microcontroller code.It also makes combining two of these sensors to drive a single readout possible.A milling machine will usually have a vertical quill, as well as being able to move either the knee or whole milling head up and down.This complicates things if you have a digital readout on the quill, and a second digital readout on the knee or milling head.Move one, and you lose your zero on the other.By combining the outputs of two quadrature encoders its possible to move both or either without losing your zero.This would be very much more difficult to do with a pair of direct reading caliper readouts.