Pt100 temp woes

Sakey · 15 Apr 2017, 10:22

I seem to have a problem with my PT100 sensor and cant really pinpoint what is causing it.

I followed DC's guide and did everything but when I get to printing the temperature seems to fluctuate like I have a loose connection. This cant be replicated when not printing though (i did the jiggle test ). Its odd because its stable until it starts to print. Caused a print to fail when it over shot the safe temp limiter with one of its spikes.

Any Ideas?

Edit: I should mention have I seem to have had nothing but problems with the sensor since I got it. I have rewired it twice and changed to a cat5 cable as its constantly changing temperature. better than it was but not perfect as you can see in pic…

dc42 · 15 Apr 2017, 12:18

Do you have it wired in 2-wire or 4-wire mode?

Where the temperature rises sharply a little, that suggests you are using 2-wire mode and you have a poor connection. Where it has dropped rather more slowly, that's probably the fan coming on, or the print deflecting print cooling air over the heater block.

To eliminate interference from the extruder motor wiring as a possibility, you could try printing with the extruder motor disconnected (turn the power off before disconnecting it).

Sakey · 15 Apr 2017, 13:04

Cheers DC, Its running in 4 wire mode and for this print the fan is constant. It was as peaking at 400c. I've made sure the wires are running their own track away from anything but i'll give the disablling the extruder motor a go. I think it is a lose connection to be honest but everything seems secure and can't replicate it when the print isn't going( wiggling wires etc).

gzcwnk · 18 Apr 2017, 07:03

I had this and it was electrical interference from the extruder stepper when it ran. Running dual shielded super flex microphone cable fixed it for me.