linear rotary encoder

I’m will be trying to control a hydraulic motor and the existing analog encoder is a … ncoder.asp

The unit is 360 degree angular range version (1024 bit).

I’ve ordered the RMC150-h1 and need to know is there an option for this kind of rotary feedback?



For rotary feedback, the RMC supports quadrature (A+,A-,B+,B-,Z+,Z-), SSI, or resolver. The RMC does not support rotary analog feedback.

For absolute rotary feedback, we recommend using an SSI encoder. For incremental feedback, we recommend quadrature encoder feedback.

For rugged transducers and small form factors, resolvers work as well, although the Resolver module on the RMC150 is more expensive than the other modules, and there are some velocity limitations with resolvers (3000 rpm for 14-bit resolution, 600 rpm for 16 bit resolution).

I was afraid of that, I do have the SSI version … ncoder.asp
of that encoder, does your SSI module cover it as well?

Is it possible to add it to the H1 module in the future?


I looked in the datasheet, and it will not work due to some ways the signal works that are not really standard.

Unfortunately, we have no plans on providing rotary support for analog feedback. Analog is rather noisy, and that can present problems with rotary control. Quadrature, SSI, and resolver are better suited, and are more common as well.

So, it seem this product will not work with the RMC. Is there a specific reason you want it, such as size? Do you know of other encoders that you can use?

I also want to just verify that you are using the hydraulci motor for multiple revolutions. Occasionally, someone uses a motor for less than one revolution, in which case, the rotary support is not required.

Not Work? Why?

I have two modes for the hydraulic motor, cyclic, follows a sine wave, max 180 degree rotation. Then I have variable speed mode in constant rotation in one direction, which could be in open loop.

Thanks again,

The RMC expects a stop bit after the data is complete. Since the RMc cannot use the status bits, it must send only 10 clock bits. However, it also requires a stop bit to be low after the data. When sending only the 10 bits, the next bit sent by the AMCI is the status bit, not the stop bit.

Another problem is that the AMCI sets the data line low when receiving the first clock pulse. The RMC expects the data line to be high until the first data bit, which is after the second clock pulse.

I called AMCI to verify that the device actually behaves this way. They informed me that it does, and gave me the part number of the chip they use that generates the SSI signal (, … ers/AS5043).

We are confused as to why the chipmaker would make an SSI output that is not in line with the SSI standard as originally designed by Stegmann ( Unfortunately, we have been seeing more and more non-standard SSI designs. We hope to eventually make modifications to our SSI design to accomodate some of them, but it is very difficult to foresee what other non-standard changes will be made.

For your constant rotation in one direction, even if it is open loop, it would be much easier to do with a rotary device compatible with the RMC (see [url]SSI Rotary Absolute Encoders]). You could perhaps do it with the analog device you have, but then you would have to disable some of the error functionality, and in general it would not be as nice as it otherwise could be.

The AMCI is a nice small, robust, IP67 encoder and it was cheap. It’s the first time for SSI for me though. Will be looking for another compatible SSI unit.

Have you guys have an updated list of SSI encoders other then what’s posted on your web site?

Thanks for your help.

Unfortunately, we don’t have anymore than what is listed on the site. We do appreciate suggestions.

Thank you,

Jacob Paso

Iv’e found a mechanically same encoder

How do I found out if they have gone off SSI standard?

Thanks again.

I called and left a message asking for an SSI timing diagram. We’ll have to see how long it takes for them to get back.

Received the email dialog from Tim and Dan at and got the thumbs up. Do you concur?

I understand they are going to send you a sample to test. Please post your results.

Thanks again,

Yes, it appears that it will work. It sounds like they’ll send you one first. It may not be until release time that they send me one.

The encoder works! :smiley: :smiley: :smiley: :smiley:

Cool! Hopefully we will get one here soon.

I also updated our SSI Rotary Encoders recommendations page: [url]SSI Rotary Absolute Encoders]