How find correct M305



  • Hi,

    i have changed thermistor of nozzle, and i am having issues with extrusion.... i can try some things.... but i suppect that Nozzle temperature sensor its not given me the correct values....

    How i can fin the correct values for my temperature sensor?

    In this moment, i have:

     M305 P0 S"Cama" T100000 B4138 C0 R4700 ; Set thermistor + ADC parameters for heater 0
     M305 P1 S"Extrusor" T100000 B4138 C0 R4700 ; Set thermistor + ADC parameters for heater 1


  • datasheet or measure the resistance at two known temperatures with a multimeter. (water saturated with ice and water at a rolling boil are the two easiest diy temperature refrences).

    link to calculator to help work out the beta value https://www.ametherm.com/thermistor/ntc-thermistor-beta



  • Buff.... not easy...

    i have access a cooking thermometer ...

    I can select a temperature in the DWC, and see the actual temperature with the kitchen thermometer.

    The circumstance is, for example, I start in config.g with:

    M305 P1 S "Extruder" T100000 B4138 C0 R4700

    A- I select a temperature of 200º in DWC
    B- When in DWC has reached that temperature, I measure the temperature with the kitchen thermometer, and for example I read 180º.

    What value of the line M305, would have to adjust so that the temperature that I see in DWC 200º, approaches the real measure with the kitchen thermometer 180º?

    How do the different parameters of M305 affect the reading of the temperature?



  • the easy solution is to buy a thermistor with a datasheet, the other solutions are to measure or trial and error.



  • @bearer think o will do trial /error.... Beta value, suposse is B in M305. No?



  • Another option.... That someone have used before... Buyed termistor in aliexpess, lThist...

    In some point of description males refence as model B3950.... Maybe.... Later try



  • in the absence of testing, with the infrared thermometer, I think I've found it ..., or almost I am in the way
    I've changed in config. G the value of B in M305, by which he puts in the description of the product in Ali Express ... and now the temperature only goes 0.1 degree, with which he reads the bed ...



  • @peirof said in How find correct M305:

    Buff.... not easy...
    i have access a cooking thermometer ...

    You can use 0C and 100C calibration points using water as described here https://www.tegam.com/how-to-calibrate-a-temperature-probe/ and other places.

    If you are not close to sea level you may need to adjust the values accordingly.



  • Hi,

    today test.... something still wrong.

    I have a multimeter with temperature sensor included... supposing its working ok....

    1- I have put in config.g this line: M305 P1 S "Extruder" T100000 B3950 C0 R4700, the main change its B3950- Why i have put this valour for Beta, because where buy it, say it...
    2- I have a multimeter... this multimeter has a temperature sensor... let thinking its working ok, the readings are correct.
    3- I have do a "test range", with a old heater block, a heat cartdrige, termistor and temperature sensor of multimeter...

    And i have do the test...

    4- I have, by DWC, temperature of Nozzle raises 50º.... and start raising.
    5- When tempearture reaches, this stops raise, arround 50º... but the readings in tempearture sensor of multimeter reach arround 70º, 20º degrees more of commanded. This have sense... For this the clogs, the filament fuses in heat sink, and produces clogs...

    Provisional conclusion

    I have wrong B value.

    How affects B value to readings, the idea its do a trial/error, until discover correct value....

    If i want that Duet reads more temperature that actual read.... what i have to do? Raise B? How many?

    thanks



  • @bearer said in How find correct M305:

    datasheet or measure the resistance at two known temperatures with a multimeter. (water saturated with ice and water at a rolling boil are the two easiest diy temperature refrences).

    link to calculator to help work out the beta value https://www.ametherm.com/thermistor/ntc-thermistor-beta

    if you can measure both the resistance of the thermistor, and the temperature this should help you find the correct beta value.



  • @peirof said in How find correct M305:

    I have put in config.g this line: M305 P1 S "Extruder" T100000 B3950 C0 R4700, the main change its B3950- Why i have put this valour for Beta, because where buy it, say it...

    the value of B3950 is for the range from 25C to 50C.
    however they tend to differ by quite a margin at temperatures in the range of the hotend.

    my suggestion to you is to replace the thermistor with a know one.
    like a Semitec 104gt-2


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