BEI sensors gray code absolute encoder

[m_primucci]

Hi,

Currently i have a Nemicon 10 bits Gray code absolute encoder, and the conversion between Gray code to binary code works fine.

Now, we buy a BEI sensors, CHM5, 10 bits gray code absolute encoder and the conversion seems to be wrong.. There are a different Gray code codification? I read in another forum that some encoders need a NOT input for gray bits...

Someone works with those encoders? There is a different codification methods?

Thank you and best regards!!

 

[widelto]

Just check P/N of new encoder to be sure that specs are the same as the old one.

 

[bernie_carlton]

The documentation at BEI for the CHM5 type encoder shows an SSI transmitted signal using RS485 type pairs. It said nothing about the resultant code being in the Gray Code format. Do you have a system which receives an SSI signal?

Edit - after further Googling I see that the CHM5 comes in SSI and parallel format. Assuming it's a parallel then, if it says Gray Code then it can have only one format. I'll assume both are 1024 bits per revolution. If they are of a different resolution then please post.

 

[shooter]

gray code is not defined fully, so the bits can be on a different position.

 

[bernie_carlton]

For more precise help please supply the complete part numbers for both encoders.

 

[m_primucci]

Encoder code

Hi,
Thanks to all for the answers!!

The codes are:

Old: Nemicon ASC-SP10-GT, H10-200-00, 10 bits gray absolute encoder

New: BEI Sensors CHM5_10//5C5G//10//C3R020 (parallel Output)

Best regards

 

[bernie_carlton]

The Nemicon shows "Negative Logic" for its output. Also the BEI outputs for 10 bit would be 'D3' to 'D12' (pins 6-15). Did you take these into account?

 

[m_primucci]

The Nemicon shows "Negative Logic" for its output. Also the BEI outputs for 10 bit would be 'D3' to 'D12' (pins 6-15). Did you take these into account?

The first thing it is interesting, if the former logic have this fact into account (i didn't do this part), the channels must be "negated" when the conversion to the binary system is done, right? And if then the BEI encoder have "direct logic"... everything goes wrong. Let me check with the former logic...

About the second: yes, the BEI encoder uses the D3 to D12 pins only, the first 3 are totally useless (no changes during a turn).

Thank you in advance for your answers!!

 

[bernie_carlton]

The 'negating' would have to occur before the conversion from Gray to binary takes if a standard function was used.

If a hand coded Gray to Binary function was coded (and it isn't very hard to do) then they may haven taken the negative logic into account when writing it.

You wouldn't actually use 'negate', you would need an 'invert' function. Be sure to not invert bits not part of the input.

 

[m_primucci]

The 'negating' would have to occur before the conversion from Gray to binary takes if a standard function was used.


You wouldn't actually use 'negate', you would need an 'invert' function. Be sure to not invert bits not part of the input.

Thanks for your answer!!! It was the "invert" function before the gray to binary conversion and once I removed, everything goes right..

One important thing: this BEI encoder has a direction bit (white/Blue cable), if the encoder have one direction of movement, it is highly recommended that you connect to 0 V (white) or +V (brown) depending on direction, because if you leave free and accidentaly goes to ground, the direcion of counting can be inverted (this haapen during test).

Thanks a lot and it was very useful this post!!!!