Thank you @oliof! I walked around the université for ferrites but it worth it.
After connecting one ferrite in the power input of the power input of the Scanner, the noise was reduced in this device but it still is not enough to get a good value
I noticed the noise in the temperature sensors didn’t changed, so I added a second ferrite in the power input of the Duet 3 Main Board 6HC. Now I have noise-free temperature readings
I will wait for the filters and try to get someone with électrique knowledge to see what is happening. I will update this post once there are news.

Some good news! (sorry if I don't use the right technical terms).

More information about the printer that electrical members mentioned:

• the motor cables are long (more than 2m for Y and more than 1m for X) and not shielded (we changed this at the end).
• the X and Y motors are bigger than needed (we are moving them with 2.5A but they are least 6A).
• the 24V cable to the Board 3 6HC is 1m and I belive there are 5m to the scanner.

Yesterday, we removed the ferrites and measured with a probe the 24V line. Just turning on Y motor was enough to see how the noise increased a lot. As the motor cables and the 24V cables travel next to each other in the printer, they believe there is interferance. The next step was to change the motor cables for shielded ones and it improved the results.

Today, the line filters arrived and after installing them, the problem seams to be solved. One filter is close to the extruder+scanner and one is the Board 3 6HC.

Some good news! (sorry if I don't use the right technical terms).

More information about the printer that electrical members mentioned:

• the motor cables are long (more than 2m for Y and more than 1m for X) and not shielded (we changed this at the end).
• the X and Y motors are bigger than needed (we are moving them with 2.5A but they are least 6A).
• the 24V cable to the Board 3 6HC is 1m and I belive there are 5m to the scanner.

Yesterday, we removed the ferrites and measured with a probe the 24V line. Just turning on Y motor was enough to see how the noise increased a lot. As the motor cables and the 24V cables travel next to each other in the printer, they believe there is interferance. The next step was to change the motor cables for shielded ones and it improved the results.

Today, the line filters arrived and after installing them, the problem seams to be solved. One filter is close to the extruder+scanner and one is the Board 3 6HC.

Thank you @oliof! I walked around the université for ferrites but it worth it.
After connecting one ferrite in the power input of the power input of the Scanner, the noise was reduced in this device but it still is not enough to get a good value
I noticed the noise in the temperature sensors didn’t changed, so I added a second ferrite in the power input of the Duet 3 Main Board 6HC. Now I have noise-free temperature readings
I will wait for the filters and try to get someone with électrique knowledge to see what is happening. I will update this post once there are news.

Hello!
We have a X1000 Y1000 Z30 printer to study the behaviour of filaments in the first layer. We installed a laser scanner next to the extruder and we are having some problems. Maybe you can help us!
We have a Duet 3 Main Board 6HC with the PT100 Daughter and a Duet 3 Tool Board. Two big motors and one smaller are connected to Main Board with a lot of temperature sensors. The extruder is controlled by the Tool Board (disconnected until we fix this issue). The bed and ambient temperature are controlled by another device.
We have a new 24V-20A power supply (just changed due to this issue) that powers the two boards and the laser scanner. When the motors are off, the output of the scanner presents no noise at all, but once we turn on the XYZ motors the output is useless. We noticed that some sensors present some temperature noise too.
We tried a similar setup in a smaller printer without issues, so we believe is something related to the wiring.
We tried different groundings and checked every single connector. The current grounding is similar to this one : https://forum.duet3d.com/topic/6498/grounding-kossel-mini-frame/4 (consider that the extruder is disconnected for now).
We also tried disconnecting the Z motor that is close to the scanner, but same result...
The scanner supplier suggested that there may be a power supply or a electromagnetic problem. We changed the power supply and the problem is still there. We ordered some DC line filters but we are looking for suggestions that we can try in the next days.
Thanks!