Slice Thermistor Config Issues - Again



  • M308 S1 P"e0_temp" Y"thermistor" T500000 B4723 C1.196220e-7    ; Slice high temp thermistor from configurator
    M308 S1 P"e0_temp" Y"thermistor" T500000 B4682 C1.143895e-7     ; Slice from DC42 thread with forum member

    I know this has been covered before and I have tried both of these M308s with my Hemera and copper heat block. However in both cases the temperature I read on 2 different thermocouple meters( a fluke and another nist traceable meter) are 14 degrees below what dwc shows @220c. The thermocouple probes were under the silicone sock next to the nozzle. No portion of the leads leading to the probe were exposed. I have used these meters and technique on v6’s and never read more than 3-4 degrees cooler than dwc read.
    Is there any way to just configure an offset? The difference @250 is 16 degrees so close to the same. Thx



  • Unfortunately there isn't to my knowledge .... it would be a great idea to have an offset that is configurable. There are the L*** and H*** parameters for M308 but when I was trying to correct for an offset, they were highly unsatisfactory. I ended up tweaking the B parameter until the displayed temperature was within a reasonable margin of what my independent meter showed.
    Just try and add or subtract 200 from the B value and you will quickly see if you need to add or subtract to the original value to get you into a better ballpark.
    The actual temperature that is displayed isn't really terribly important and only needs to be better calibrated if you run multiple printers and you run the same filament on more than one printer so that you can transfer the settings used on one printer to the next printer without having to tune the settings for each printer seperately.



  • Different to the normal E3D thermistor? Your C value looks out?

    Screenshot_20200228-074208.png



  • @DocTrucker A Slice Engineering thermistor is different to a Semitec 104 or whatever it is that E3D use. I believe that it can go to very high temperatures.



  • @deckingman Hemera = The extruder formerly known as Hermes = E3D?

    Edit: Missed the "Slice" in the title! 😄



  • In that case have a read through calculating the Steinhart-Hart values. Seems you've got a temperature sensing test equipment you can trust?

    Here's a start:

    https://www.thinksrs.com/downloads/pdfs/applicationnotes/LDC Note 4 NTC Calculator.pdf


  • administrators

    @4lathe said in Slice Thermistor Config Issues - Again:

    M308 S1 P"e0_temp" Y"thermistor" T500000 B4723 C1.196220e-7    ; Slice high temp thermistor from configurator
    M308 S1 P"e0_temp" Y"thermistor" T500000 B4682 C1.143895e-7     ; Slice from DC42 thread with forum member

    I know this has been covered before and I have tried both of these M308s with my Hemera and copper heat block. However in both cases the temperature I read on 2 different thermocouple meters( a fluke and another nist traceable meter) are 14 degrees below what dwc shows @220c. The thermocouple probes were under the silicone sock next to the nozzle. No portion of the leads leading to the probe were exposed. I have used these meters and technique on v6’s and never read more than 3-4 degrees cooler than dwc read.
    Is there any way to just configure an offset? The difference @250 is 16 degrees so close to the same. Thx

    If possible, I suggest you check the calibration of the Duet by substituting a fixed resistor for the thermistor and checking the reading. The R-T table for the Slice thermistor can be downloaded from https://www.sliceengineering.com/pages/documentation. So a 1K resistor should read close to 280C, and a 2.2K resistor should read close to 230C.

    You can choose the T, B and C values in RRF to get the reading to match a R-T table exactly at any 3 temperatures. These temperatures should be fairly widely spaced so as to get reasonable accuracy over the entire range of interest to you. For example, if I choose 25C, 200C and 400C then the calculated parameters are T500000 B4723 C1.196220e-7, which are the values used in the preset in the online configuration tool. Using these values, the maximum error over the range 25C to 500C is -0.7C which occurs at 250C.

    I have found it difficult to get accurate readings for thermocouples touching the heater block. The problem is that it's hard to get good thermal contact between the thermocouple tip and the heater block, and the thermocouple leads conduct heat away from the tip.

    Which Duet are you using, and which firmware version?



  • Using Duet wifi and 3.01 rc2. I will get the resistor and start with checking that.



  • @dc42 just to wrap this up, I got the resistors. The values with the 1k and 2.2k were with .5degrees. I then redid the t,b,c values using the slice table but at a narrower range - 190 to 270. The results with the 2 meters are now 2.5 degrees low at 220. Good enough for the government. My printing is all close to that anyway.
    Thx for the help!


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