NTC 3950 Cartridge HT-NTC100K how to config ?

dc42

You can use B3950 C0 in your M305 P1 command. However, as there are no resistance/temperature tables published for that thermistor, and quoted B values are normally only valid at quite low temperatures (e.g. 25c to 75C), expect the temperature readings to be inaccurate at typical printing temperatures.

darrklogik

Hi There. I recently purchased a Keenvo 240 VAC silicon bed for my CR-10 5S from aliexpress. They supplied the HT-NTC100K B3950 thermistors with the bed, and a data sheet for this representing Temperature @ given resistance value. Please see attached pdf. I hope this helps you guys. Note, I replaced my standard 12VDC bed with this new keenvo bed, and simply cut and soldered the existing thermistor sensor wire leads coming from the CR-10 computer box. I threw the old metallic hotbed with its doublesided tape stuck-on thermistor out. I figured I didn't need it anymore. After firing it all up, it worked magically. I didn't configure any settings or reflash any firmware. I matched the temperature display with a laser IR gun, and they matched. I guess I got lucky. Octoprint also reported the same temperature as the IR gun. There was a few degrees difference, but once it all stabilized, the temperatures matched.

0_1541668153724_NTC-Thermistor-R-T-Table.pdf

darrklogik

Temperature/Resistance tables for the HT-NTC100K B3950 thermistor straight from china land.

The guys on the keenvo store via the Aliexpress phone APP gave me this pdf datasheet. Hope it helps you guys set this up for the Duet3D board!

After looking at the latest Marlin Firmware, I noticed the thermistor for the CR-10 5S 12VDC hotbed is set to "no# 5":

5 : 100K thermistor - ATC Semitec 104GT-2 (Used in ParCan & J-Head) (4.7k pullup)

So you would define your extruder thermistor like so:
#define TEMP_SENSOR_0 5

Maybe it matches the resistance/temeprature curve at lower temperatures? Looking at the "ATC Semitec 104GT-2" thermistor table, it does look different. See attached PDF.

At 0 deg celcius, they differ by 26 ohm (out by ~1.5 deg c)
At 10 deg celcius, they differ by 8.6 ohm
At 20 deg celcius, they differ by 1 ohm.
At 30 deg celcius, they differ by 2.7 ohm
At 40 deg celcius, they differ by 2.5 ohm
At 50 deg celcius, they differ by 2.4 ohm (out by 2 deg c)
At 60 deg celicus, they differ by 2.5 ohm
At 70 deg celcius, they differ by 2.1 ohm (out by 4 deg c)
At 80 deg celcius, they differ by 1.7 ohm (out by 5 deg c)
At 100 deg c, they differ by 1.2 ohms (out by 8 deg c)
At 150 deg c, they differ by 0.41 ohms (out by 14 deg c)
At 200 deg celcius, they differ by 0.5820 ohm - 0.4393 ohm = 0.1427 ohm (out by 18 deg)
At 240 deg celcisu, they differ by 0.2737 ohm - 0.2065 ohm = 0.0672 ohm (out by 15 deg)

Looking at the data extract above, its reasonably accurate at lower temperatures. I would say 0 deg c up to 75 deg c. However, its get more innacurate above 100 deg c., and gets steadily worse. It's definately unusable above 200 deg c. So you could use marlin thermister Type No# 5, for the HT-NTC100K B3950 thermistor, for temperatures below 100 deg c for the hotbed for example.

Links to datasheet:
[https://e3d-online.com/100k-ohm-ntc-thermistor-semitec](link url)
[http://www.atcsemitec.co.uk/gt-2-glass-thermistors.html](link url)
[https://www.keenovo.com/NTC-Thermistor-R-T-Table.pdf](link url)

0_1541669367568_GT-2-glass-thermistors.pdf

0_1541668949826_NTC-Thermistor-R-T-Table.pdf

dc42

If you have the resistance vs. temperature table, go to the configurator at https://configurator.reprapfirmware.org/, then the Heater page, then click on "Calculate thermistor coefficients or choose preset". Enter the resistance and temperatures at 25C and at 2 other point of interest from the table, for example the upper and lower temperatures that you normally use while printing. The calculator will then tell you the beta and C values to use. For example, if I enter the nominal resistance at temperatures of 25C, 190C and 250C from that table, I get beta=4130 and C=1.739356e-7.

darrklogik

It looks like the No# 60, #11 or #13 in the Marlin firmware is the correct one to use for the HT-NTC100K thermistor. Im not sure what it is in the Repetier firmware though... As long as the Beta is 3950 it should be good to go...

Veti

unfortunately it is unclear what actual thermistor is been used when it says HT-NTC100K.
the value of 3950 applies to low temperatures and can lead to been quite far off at high temperature.

marlin uses a beta value of 4100 for the Hisens 3950 1% up to 300°C for hotend.
and if found this to be more fitting for my catridge

I have found one table for this on aliexpress and from my calculation i came up with a beta value of 4066.
https://www.aliexpress.com/item/1PCS-trianglelab-Thermistor-Cartridge-350-for-E3D-hotend-v6-heater-block-Maximum-support-to-350-degrees/32843785247.html

but looking at the range above 200 degree you get an accuracy range from -6% to + 6%. Thats a range of 24 Degrees.

With the problems that has caused me i decided to order a pt1000 and try my luck with that.

dc42

@veti said in NTC 3950 Cartridge HT-NTC100K how to config ?:

unfortunately it is unclear what actual thermistor is been used when it says HT-NTC100K.
the value of 3950 applies to low temperatures and can lead to been quite far off at high temperature.

marlin uses a beta value of 4100 for the Hisens 3950 1% up to 300°C for hotend.
and if found this to be more fitting for my catridge

I have found one table for this on aliexpress and from my calculation i came up with a beta value of 4066.
https://www.aliexpress.com/item/1PCS-trianglelab-Thermistor-Cartridge-350-for-E3D-hotend-v6-heater-block-Maximum-support-to-350-degrees/32843785247.html

but looking at the range above 200 degree you get an accuracy range from -6% to + 6%. Thats a range of 24 Degrees.

See my earlier post about how to use the configurator to find suitable B and C parameters for the M305 command if you have a R-T table for the thermistor. That will give you more accurate readings than just using a B value.

Veti

unfortunately i don't have the thermistor table for mine.
I thought about getting a Digital Laser Infrarot Thermometer, but the pt1000 was cheaper
For now i use the Marlin value which seems to work.

ignacmc

@dc42 Please correct me if I am wrong, but if I enter the following values in the Configurator:

T1: 25ºC R1: 100000 Ohm
T2: 190ºC R2: 719 Ohm
T3: 250ºC R3: 230 Ohm

These values should be the same as yours as they are taken from the NTC-100K datasheet by Keenovo.

Then I obtain BETA= 5041(vs your 4130) and C=1.739356e-7 (same as yours)

What I am doing wrong?

dc42

@ignacmc using https://www.thinksrs.com/downloads/programs/therm calc/ntccalibrator/ntccalculator.html I get 1/B = 5041 too. The 1/B value is the value you should use for the M308 B parameter when you also give the C parameter.

However, it might be better to pick a lower temperature for the middle value, e.g. 150C. The datasheet gives the resistance as 1770 ohms, which gives 1/B = 4981 and C = 1.63283e-7.

ignacmc

@dc42 Thank you David for your quick answer and sorry for reopening a thread almost 3 years old

I usually print in ABS and since T3 is not used for BETA calculations, I had thought to use T2=255 ºC as the middle value, and T3=290 ºC since it is the theoretical maximum hot end temperature...Am I doing right?

By the way, both the RRF configurator and the SRS Thermistor Calculator use a default value of 10K (10,000 Ohm) instead of 100K (100,000 Ohm) for R1, which can induce to errors for a NTC100K thermistor.

Using the values of:

T1=25 ºC R1=100000 Ohm
T2=255 ºC R2=211.4 Ohm
T3=290 ºC R3=122 Ohm

I obtain quite different BETA values: 4956 in the RRF Configurator and 4216 in the SRS Thermistor Calculator. How can this be?

I understand that the line to use in config.g should be like:

M308 S1 P"e0temp" Y"thermistor" T100000 B4956 C1.587780e-7

Thank you in advance for your time.

dc42

@ignacmc the Beta value given by the SRS calculator is for when you want to ignore the third temperature-resistance pair and not use a C parameter.