Showing results for 
Search instead for 
Did you mean: 

Strange software behavior for absolute encoder decoding

Go to solution

Hi all

First of all.. Sorry for my bad english.. 

My software is behaving quite strange...

I have a test set-up with a driveline with a gear placed as illustrated in "System set-up".

I have two 32 bit absolute encoder rings (the encoder rings has different diameter) and 4 identical renishaw readheads.

The readheads are connected to two SEA 9521 module on a cRIO-9047.

In order to decode the raw data input from the readheads I'm using the software examples made by the SEA company.

I have attached the code in a ZIP file (I'm using the file "SEA-9521_GetPosition_Standard (FPGA)/SEA-9521_GetPosition_Standard (FPGA)_FPGA")

I did put in the right module configuration as shown in "Front panel" below.

The problem / strange behavior is the following:

- The software are working perfectly when configured for R3 and R4. R3 goes from 0 -> 360 deg, R4 goes from 0 -> 360 deg
- If I switch to R1 and R2 only one of the readsheads are working properly (though all readsheads are wirred the same way). (R1 goes from 0 -> 360 deg, R2 goes from 0 -> 192 deg ish)
- If I on the block diagram switch position of the readheads in the I/O Node R2 goes from 0 -> 360 deg and R1 goes from 0 -> 192 deg.
- When the software are working for R3 and R4.. Why isn't it working for R1 and R2???

I really need help for this one...

Thanks in advance!

0 Kudos
Message 1 of 4

Hey mkstech, 


You're english was perfect 🙂 

I'd try reaching out to SEA gmbh Technical support as they're going to have the best knowledge of the project examples. 

Their website has a support link here or an email


Best of luck!

0 Kudos
Message 2 of 4

Wild guess...


Could this be a timing issue?


Does slow it down help?



Retired Senior Automation Systems Architect with Data Science Automation LabVIEW Champion Knight of NI and Prepper LinkedIn Profile YouTube Channel
0 Kudos
Message 3 of 4
Accepted by topic author mkstech

Hi Ben

We managed to figure out what the problem was.. 

The readhead which didn't work was actually only suited for an encoder ring with a larger diameter (100mm)... 


And the encoder ring we had was 52 mm 🙂

0 Kudos
Message 4 of 4