Linear quadrature encoders
Linear quadrature encoders
(OP)
I was recently looking for a cost effective linear quadrature encoder for measuring position of a press with a PLC. Basically I wanted something resembling a pneumatic cylinder, relatively rugged, with a straightforward quadrature interface. Absolute encoding would be a plus... Stroke needed is 14 inches.
I was surprised how hard it was to find something clean. Inductosyn devices seemed like a nice option, but it seemed their output signal options were bizarre; translators would be needed to get to useful signals, plus their mounting is sort of awkward. There were some options that had a physical sliding connection on the SIDE of the cylinder... very awkward mounting! String pot style encoders were another option, but the string seemed somewhat delicate and how do you zero them? Linear pots require analog inputs, and noise could be a problem.
I ended up with linear digital quadrature encoders from an Italian company Elap (http://www.elap.it/) which are available through a US distributor (http: //www.ghbi nroth.com/ Elap/Elap_ Linear_Inc remental_T ransducers). They are < $400 for 14 inch stroke devices. They aren't quite as rugged as I would like, but they should last for a while. One nice feature is that they have an optional index pulse at midstroke. By simply cycling my press through mid-stroke I have in essence an absolute encoder, with no limit switch BS required!
I'm just curious if anyone knows of similar devices I missed. Plus it would be nice to have an alternate part available. The month long August holiday in Italy was a bit of a pain (since I wasn't included!).
Thanks.
I was surprised how hard it was to find something clean. Inductosyn devices seemed like a nice option, but it seemed their output signal options were bizarre; translators would be needed to get to useful signals, plus their mounting is sort of awkward. There were some options that had a physical sliding connection on the SIDE of the cylinder... very awkward mounting! String pot style encoders were another option, but the string seemed somewhat delicate and how do you zero them? Linear pots require analog inputs, and noise could be a problem.
I ended up with linear digital quadrature encoders from an Italian company Elap (http://www.elap.it/) which are available through a US distributor (http:
I'm just curious if anyone knows of similar devices I missed. Plus it would be nice to have an alternate part available. The month long August holiday in Italy was a bit of a pain (since I wasn't included!).
Thanks.





RE: Linear quadrature encoders
For that, I have used Tempsonic transducers. http://www.mtssensors.com/index.php?id=130
They are absolute and rugged. Easy to install and easy to interface. Analogue output is the simplest. There are bus versions also. Not too expensive.
I used four of them with 1000 mm stroke to measure position of press tables in a press where temperature was an issue. Worked very well.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Linear quadrature encoders
Keith Cress
kcress - http://www.flaminsystems.com
RE: Linear quadrature encoders
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Linear quadrature encoders
Keith Cress
kcress - http://www.flaminsystems.com
RE: Linear quadrature encoders
Their mounting also seems awkward for a retrofit... a ridgid shaft with a ring around it? I see they do offer one unit enclosed into a package similar to a linear pot (resembling a small air cylinder). But that unit has very limited output signal options. I can go analog (current would offer reasonable noise resistance) but would need a 15 bit A/D to match the resolution of the Elap digital sensor. You won't get that on an entry level PLC.
RE: Linear quadrature encoders
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Linear quadrature encoders
RE: Linear quadrature encoders
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Linear quadrature encoders
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In the early days (1980's), the output signal was a design unique to the technology of LDT's - Magnetostriction. However, today standard output signals are available.
MTS invented the technology, but Balluff also has a very nice product line with different profiles and standard analog outputs such as 0-10V and 4-20mA.
They are easy to apply and accurate enough for most applications.
They are also rugged. I have used them in Plywood and Brick plants.
I love to use them whenever I have a linear application.
RE: Linear quadrature encoders
FYI, this link describes the technology:
http://
RE: Linear quadrature encoders