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PTC probe extension , considerations


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Hi ALL,

I need to run a longer cable from the PTC bricklet to the the PT100 probe (the one from your shop).

I used 2 x1mm^2 sensor cable  to extend the 1m that comes with the probe. 7m long.   

Do you think that can affect the results much?

I have some concerns , as that is an important readout I have 2 sensors in exactly the same location, glued together with a thermal glue into one blob attached to the pipe.

They are about 1-1.1 degree apart, and output looks a bit noisy.  (I read them every 2 seconds)

image.thumb.png.141f312d816b3997019967a50f7460f5.png

What do you think?

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Hi,

as far as I understand your description you use a 2-wire probe, right? For a 2-wire probe there is no wire resistance compensation. One possibility would be to connect the 2-wire probe with 4-wires, such that you can compensate for the wire resistance.

Regarding noise a longer cable might induce more noise. In this case a 4-wire connection should also improve the situation.

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  • 2 weeks later...

Ok so I rewired the setup and now 2 sensors (Output 1, Output2)  are 4 wire (7m extension).  3 named Noel are old setup (2 wire 7m extension).

And for comparison I added Poiol skimmer to the graph that is same PTC probe on 2 wire directly to PTC bricklet  on the same RPI HAT. 

As you can see the extension is the problem , adding 2 wires did not improve the noise. Probe directly into the bricklet is super clean.

What else could be a problem here?

TIA

 

image.thumb.png.c14a48b55c54f46d68dce2da7e433f75.png

Edited by xsherlock
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Hi Sherlock,

is it possible that you send me a picture of your extension? The connection at the sensor and at the Bricklet is what I like to see.

I'm pretty sure that you have done that right, but sometimes it is much easier to see it on a picture that to explain it by words.

You have configured the PTC Bricklet for 4-wires, right?

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