Help with Slice Engineering 300º Thermistor on Duet 2

[st3phen]

I purchased a Slice Engineering 300º thermistor for use with my Duet 2 Wi-Fi, replacing an E3D thermistor.

It came with a dire warning about requiring configuring firmware for it. It says to choose "100K thermistor - ATC Semitec 104NT-4-R025H42G" in the Heater tab of the RepRap Configurator. There is no thermistor of that type in the table. There is a Slice High Temperature Thermistor preset, but that is meant to be used with the 450º thermistor, not my 300º thermistor. The values of the 300 and 450 are very different!

I also tried to generate a Custom Heater Parameter on the configurator, but its results were very different from what Slice provides.

These are the RT firmware tables Slice provides.

The table shows an R25 value of 100,000Ω ±3% and a ß value of 4267 ± 2%.

The M308 command I've devised is this:

M308 S1 P"e0_temp" Y"thermistor" A"Mosquito" T100000 B4267 C0 R4700	; configure Sensor 1: Hotend temp: pin_name, sensor type, DWC name, thermistor resistance @ 25º, ß value, resistor value

Is that correct?

It seems that 4700 may be the correct R (pull-up resistor) value based on previous iterations of Slice's table. But, I am not at all certain what, if any, value to give to the C (Steinhart-Hart C coefficient) value.

I've searched the Duet forums, Slice's website, my printer's Facebook page, Facebook in general, and the Internet in general, and am failing to find the correct answer. Thank you.

[dc42]

@st3phen, that thermistor sounds the same as the E3D one, which is the default, as well as being an option in the online configurator.

[st3phen]

@dc42 Thank you, David. I saw the E3D item (Semitec 104-GT2) in the configurator and that it differed from the Semitec 104NT-4-R025H42G designated by Slice. The T values between Slice's 104NT and E3D's 104-GT2 are the same at 100,000, the ß values between them are similar (4267 vs 4725), and I guess I can calculate the C coefficient. But, does my M308 code seem safe enough to avoid Slice's overwrought fire hazard warning?

[Phaedrux]

@st3phen I think the Dire warning is because people will try to disable the heater protections when it doesn't work at first which is where the fire risk comes from.

If you can derive sane values for the thermistor based on what you know about it, you should be ok.