SSI linear measuring system on SMC30 module: referencing issue

I can't answer your question directly.  However, I can tell you that, if the encoder is being read properly, then the SMC30 is NOT your problem.  The SMC's are merely devices to provide interface to a telegram format.

The problem appears to be in your CU setup as to home position offset. 

Dear TechTeam,

thank you for your answer.

Please find attached the screenshot you requested.

The "LU for 10mm" is not set to 100 (according to the explanation in the Application Note, this value could be different... is right?).

The homing is made by setting p2507=2.

I've tried to set p496=30, but it seems to be disabled (I don't undestrand why; in another project I can modify it...)

Thank you for your support (I've open a case to hotline too...)

Best regards

Hi TechTeam,

the datasheet of the MTS sensor is this.

I think the problem is not in the encoder, but in the drive parametrization (as explained above, connecting the same encoder on a PLC SSI input card, it works well, without problems of any thing).

It may be usefull to see the raw data from the SSI telegram; can you explain why the modification of parameter p496 is forbidden, so it is no possible to give access to the diagnostic features?

Another thing I've not fully understood, is the meaning of XIST1 and XIST2.

Reading the Sinamics manuals, seems that XIST1 stores the incremental value of an encoder, and the XIST2 stores the absolute value. In my case, the encoder is absolute, but XIST2 register is always 0. XIST1, instead, seems to assume a value near to zero each time I switch on the system, then increases if I move the axis in one direction, or decreses (and then goes in overflow) if I move the axis in the opposite direction. It behaves as if the encoder was incremental!

Where is stored the "absolute information"? How, exactly, the position bits from SSI telegram are interpreted and converted in the internal rapresentation of the actual position? Is there a document which explain clearly this?

Thank you very much for your support,

Best regards

 Hello, I have the same problem. Did you solve it?

mircoaie3

Hi TechTeam,

the datasheet of the MTS sensor is this.

I think the problem is not in the encoder, but in the drive parametrization (as explained above, connecting the same encoder on a PLC SSI input card, it works well, without problems of any thing).

It may be usefull to see the raw data from the SSI telegram; can you explain why the modification of parameter p496 is forbidden, so it is no possible to give access to the diagnostic features?

Another thing I've not fully understood, is the meaning of XIST1 and XIST2.

Reading the Sinamics manuals, seems that XIST1 stores the incremental value of an encoder, and the XIST2 stores the absolute value. In my case, the encoder is absolute, but XIST2 register is always 0. XIST1, instead, seems to assume a value near to zero each time I switch on the system, then increases if I move the axis in one direction, or decreses (and then goes in overflow) if I move the axis in the opposite direction. It behaves as if the encoder was incremental!

Where is stored the "absolute information"? How, exactly, the position bits from SSI telegram are interpreted and converted in the internal rapresentation of the actual position? Is there a document which explain clearly this?

Thank you very much for your support,

Best regards