thermistor table data

Discussion in 'E3D-v6 and Lite6' started by danman78, Mar 22, 2015.

  1. danman78

    danman78 New Member

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    hello, I have an e3d v6 hot and that I cannot find the thermistor table that works for it. using mendal firmwareI have used table 5 table 1 and table 8. I have an external multi meter with a thermistor probe that I have tested with other hot and to determine its calibration. using table 5 the temperature was reaching about 30 Celsius below what I was setting it at around the 200 range and would grow to almost a hundred Celsius indifference at the two at range so it to 80 I was reading 200 on the multimeter. using table 8 I'm about 20 Celsius different at about 220 Celsius so when I set it to 220 its reading at 200. I've searched forums the internet this page and I just can't seem to find the solution to this problem I have other thermistor is that I can use but I would really like to keep it stock. do you have any advice for information regarding what tables to use for this hot end... I love this product and have just measured the temperature with my external thermistor in order to get the right tense but I would be glad to have it work properly with the software especially since now I am starting to print abs and the temps I have to set it to reach above safe according to the software even though it's only around 260. Thanks.
     
  2. Mike Kelly

    Mike Kelly Volunteer

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    So the thermocouple was reading 30 degrees above the thermistor?

    Are you measuring from the same point?
     
  3. licensed2hench

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    I to have been having a problem creating an accurate Thermistor Table.

    I have a modified Da Vinci 1.0 running Repetier 9.2 firmware. It uses a modified circuit for the thermistor. It adds a 10K resister in parallel to the thermistor. So I can not use the firmware preset table. This also made using many of the on-line table generating tools difficult.
    I eventual worked through the math and made my own spread sheet to calculate a table using the specifications from the link provided on the e3d website.

    The table I calculated works and I am having good results but there is a specific temperature error.
    It reads cooler them measured, growing more inaccurate as temperature increases.
    Ranging from 115°C measured at 120°C (off by 5°C) to 200°C measured at 220°C (off by 20°C)
    I am measuring at the edge between the heater block and the heater capsule. I expect a bit of a temperature difference between the surface and inside, but the thermistor reads off even when rested at room temp. Reporting 20°C measured at 24°C (both by probe and the bed thermistor).
    The measurements are consistent over multiple tries and configurations. And my filament print results seem to match the measured temperature as opposed to the reported. :|

    The thing is I can not figure out what is causing it. I have played with the math and my variables and have not found anything that could create this specific increasing temperature error. :?

    Does anyone have any ideas what factor may be causing it?
    Anyone have any experience with this kind of constant temperature error or any idea what I may be missing?

    With this printer I am having to make a lot of assumptions. Any one of these could be the source of my problem.
    1 - my math could be wrong. (Here is a link to a write-up I did on another board for anyone who wants to take a look)
    2 - my resistor values could be wrong. (I am going off the SMD codes [103]=10K, [427]=4.7K Playing with these values effects the table, but I have not found anything to match the same spread. It seems to cause greater inaccuracy at low temperatures and become more accurate as it heats up.)
    3 - the circuit could contain addition components I am unaware of. (A real possibility here, something I will investigate further.)
    4 - my bit rate could be wrong. (I am taking these values on faith as I have no way to confirm them. But playing with these values causes the number to go into wild ranges.)
    5 - my over sample rate could be wrong (I am taking these values on faith as I have no way to confirm them. But playing with these values causes the number to go into wild ranges.)
    6 - Thermistor Data. (I am using this datasheet for the 104GT values. Could I be doing it wrong?)

    Any input would be appreciated. Thanks!
     

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