Linear Encoders anyone? - Page 1
Forum section: electronics / general

author: smackaay
author_rank: Regular Contributor
timestamp: February 22, 2013, 04:51:33 am
content: So, I've been trying to design some measuring instruments in quantities of say 100 or so and I'm finding that getting linear encoders that meet my specifications are difficult to find. I was wondering if anyone has stumbled across something that might be useful because it's been an arduous journey thus far. I have found glass scales and stuff but they draw way too much power, are too large and are difficult to implement mechanically.My criteria are:Current draw 20ma or lessgood resolution/accuracy (.0005" inches or even .0001")Reasonably small size so its easier to implement since this is a handheld tool.a bit of environmental protection or resilience.I've found some stuff from austria microsystems that might fit the bill in the form of a magnetic encoder but the error on the magnetic strips is pretty high.Has any found, let's say, some excellent solutions, kind of like digital caliper sensors that are really low power, perhaps absolute or that meet the criteria? Any help is greatly appreciated.

author: AlfBaz
author_rank: Super Contributor
timestamp: February 22, 2013, 05:27:39 am
content: All I can think of for precision linear position measurement are Linear Variable differential transformers (LVDT)

author: AlfBaz
author_rank: Super Contributor
timestamp: February 22, 2013, 05:45:30 am
content: I remember reading an app note in an old National Semi Linear Applications Handbook that I have and just found it itsAN-301May be a little dated but gives you an idea of how to drive one

author: elCap
author_rank: Regular Contributor
timestamp: February 22, 2013, 05:55:19 am
content: You might find something herehttp://www.renishaw.comAs for LVDT there ones available with built in signal conditioner. Very easy to use, just apply voltage and read out a voltage prop to position.this from NI that might be useful:http://www.ni.com/white-paper/3436/en

author: fcb
author_rank: Super Contributor
timestamp: February 22, 2013, 09:59:14 am
content: I've used the AS5304 from Austria Microsystems (www.ams.com) in something similar.

author: DenzilPenberthy
author_rank: Frequent Contributor
timestamp: February 22, 2013, 11:05:11 am
content: I'd second having a look at Renishaw, they make all kinds of amazing encoders.http://www.renishaw.com/en/position-encoders--6331(But then I used to work for them so I would say that, wouldn't I?)

author: Hypernova
author_rank: Unknown
timestamp: February 22, 2013, 12:31:27 pm
content: Another vote for Renishaw from work too (linear servo motor), their sub micron resolution scales are pretty $$$ though.

author: robrenz
author_rank: Super Contributor
timestamp: February 22, 2013, 01:17:47 pm
content: Quote from: smackaay on February 22, 2013, 04:51:33 amI have built hundreds of units using the guts of the Mitutoyo absolute calipers to be used in an industrial environment. I build custom cases to house the electronics that are air purged and I just cut the scale bar off of standard calipers. In my case the customer wanted the visual display just like the caliper but if you need to interface you can use the SPC output versions and access the positional data. The other great thing about these is they only need to be absolute zeroed once. Rezero is only needed when you change a battery which is about 2 years life.

author: N2IXK
author_rank: Frequent Contributor
timestamp: February 22, 2013, 01:28:55 pm
content: LVDTs are excellent for precision linear measurements, and there are single-chip signal conditioning solutions available. Check out the AD598 and AD698 from Analog Devices.

author: smackaay
author_rank: Regular Contributor
timestamp: February 22, 2013, 01:34:05 pm
content: I looked at a lot of solutions, but never Renishaw. They have some good encoders. Thanks everyone!

author: AlfBaz
author_rank: Super Contributor
timestamp: February 22, 2013, 03:33:26 pm
content: Quote from: robrenz on February 22, 2013, 01:17:47 pmWhat a fantastic and cheap (if you dont use Mitutyo) idea... Filed away for future reference

author: jeroen74
author_rank: Frequent Contributor
timestamp: February 22, 2013, 06:48:11 pm
content: MicroE Systemsis another one. At work we use one of their sensors for micrometer precise positioning. Expensive stuff.