Duet temperature chart reading not smooth, spiky

[Sculpt Fabricator]

I have a new hot end that has 3 Pt100 sensors and the main sensor started getting
a really spiky, fluctuating, reading.
Would this be a sensor problem. or connection problem ?

[jay_s_uk]

@Sculpt-Fabricator looks like a connection/noise problem.
3 or 4 wire PT100 are less susceptible to noise than a 2 wire

[droftarts]

@Sculpt-Fabricator see https://docs.duet3d.com/User_manual/Connecting_hardware/Temperature_connecting_PT100#troubleshooting

If the sensor readings are subject to interference, some approaches to reduce noise include twisted wiring, isolation from noise sources, shielded wiring, better grounding of components. Canbus 2-wire cable has been recommended in the past, as it is double shielded with a ground core to attach to a ground pin. Check other connections, eg plugs, in the wiring for loose joints, too.

Ian

[Sculpt Fabricator]

@droftarts and @jay_s_uk
Thanks for the info, I just broke down the hot end and check the wires at the top of the sensors.
If it was interference wouldn't all three sensors be doing the same thing. They are all running the same
route to the daughter boards.

they are all two wire sensors, non shielded wiring.

after braking it down they are all smoothed out. we will see if it comes back when we start printing.

[Sculpt Fabricator]

its fine now 35 layers into the print

Is there a style of connector that people like for these sensors, I am using JST SM connectors.