Adapting 2 wire PT100 to 4 wire
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@bearer that's what's odd about the pic with the hot end. If you follow that link I put in the first post it leads to David's blog but that pic isn't there, that's why I wanted the link, so I could see the page it came from. I've searched high and low to find that info, I'm amazed you found it for me, you certainly have my thanks but can you give me the link please, I'd like to get to the bottom of why I can't see it and you can.
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@samlogan87 Thanks Sam, I read somewhere on here about the 0.4 ohms equating to 1 degree, I suppose an extra foot of wire needed to reach the controller wouldn't make that much difference as you say. I think I'll forget all about adding the extra wires, I don't have sausage fingers but I have 67 year old eyes that don't work all that well even with my reading glasses on
Keith
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@samlogan87 said in Adapting 2 wire PT100 to 4 wire:
When you actually look at the lengths of the runs we use for the printers, it is not necessary to run a 4 wire sensor.
It's not just about the length, it also helps reject the electrical noise interference from being run alongside other wires like the heaters and endstops and steppers.
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@phaedrux I would be very interested to know how much of an effect it has. We have 3 wire ones running parallel to sometimes 500A continuous loads and we don’t tend to have to many issues with temperature.
Kind Regards,
Sam -
Well going from reports here on the forum switching to 4 wire has helped some people.
I'm not an electrical engineer though. My understanding stops at 2 wires good, 4 wires better.
For what it's worth I run about 2 meters of 4 wire PT100 in a bundle to the hotend along with the heater, BLTouch, 2 fans, and stepper wires, and haven't had any issues.
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@kayjay said in Adapting 2 wire PT100 to 4 wire:
@bearer that's what's odd about the pic with the hot end. If you follow that link I put in the first post it leads to David's blog but that pic isn't there, that's why I wanted the link, so I could see the page it came from. I've searched high and low to find that info, I'm amazed you found it for me, you certainly have my thanks but can you give me the link please, I'd like to get to the bottom of why I can't see it and you can.
I combined to two for you to help illustrate the instructions in the wiki.
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@bearer Yes, it had just come to me that that was what you had done. So in actual fact, that may not be the solution. It could still be that it is wired the same as a two wire.
Never mind, I'll stick with it as a two wire, if I get discrepancies I'll search out a genuine four wire PT100
Thanks again
Keith
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@kayjay said in Adapting 2 wire PT100 to 4 wire:
So in actual fact, that may not be the solution. It could still be that it is wired the same as a two wire.
No, that photo is correct.
From the PT100 wiki page: https://duet3d.dozuki.com/Wiki/Connecting_PT100_temperature_sensors
To connect a 4-wire PT100 sensor:
Connect the two wires that go to one end of the PT100 resistance element to pins 1 and 2 (it doesn't normally matter which wire in each pair goes to which terminal)
Connect the two wires that go to the other end of the PT100 resistance element to pins 3 and 4 -
@bearer Do you mind if I add your image to the PT100 wiki?
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@Phaedrux I think that would be up to whomever I "stole" the pictures from (David/Wiki) to help illustrate.
But it that side of things is okay, then as far as I'm concerned use it as you see fit.
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@phaedrux It may not be an accurate image, unless David can confirm that is how he connected his conjured 2/4 wire PT100.
It may well be correct but without confirmation it may lead someone up the wrong path so to speak.
Keith
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@kayjay said in Adapting 2 wire PT100 to 4 wire:
@phaedrux It may not be an accurate image, unless David can confirm that is how he connected his conjured 2/4 wire PT100.
It may well be correct but without confirmation it may lead someone up the wrong path so to speak.
Keith
Yes the image is accurate.
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@phaedrux Is there actually a PT100 wiki or is it just part of another, bigger wiki. Just looked for it and can't see it. If there is one can you give me the link please?
Thanks very much
Keith -
@bearer said in Adapting 2 wire PT100 to 4 wire:
pretty much covered in the docs?
https://duet3d.dozuki.com/Wiki/Connecting_PT100_temperature_sensors
as to the why kelvin connection style is prefered is covered in detail here https://en.wikipedia.org/wiki/Four-terminal_sensing
You'll probably ignore this too, but...
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@dc42 excellent David, that settles a whole heap of concerns .... made me a happy bunny too !
