Confusion about Semitec 104GT-2 B value in documentation
-
dont confuse the beta value with the Steinhart Hart equation
https://en.wikipedia.org/wiki/Steinhart–Hart_equation
The problem with beta values is that they are only valid for the specified temperature range. ie. 25-50.
Once you go beyond that the error can become significant. There the Steinhart Hart equation will provide better results.You can not compare Beta with Steinhart Hart Constants.
-
Thanks for the reply but I do not think I'm confusing those... there is a direct contradiction in the documentation as I quoted -- that is the confusion.
-
that statement is not correct
-
@bot said in Confusion about Semitec 104GT-2 B value in documentation:
Thanks for the reply but I do not think I'm confusing those... there is a direct contradiction in the documentation as I quoted -- that is the confusion.
I agree. There is a contradictory statement. A quick gander at E3D's instructions https://wiki.e3d-online.com/E3D-v6_Assembly#Configure_Firmware_.28Easy.21.29 shows that they also recommend using the (higher) B4725 value in combination with the C7.06e-8. So my best guess is that is what we should use, despite the apparent contradictory words which state that the B value to use will be lower when a C values if also used.
-
i calculated the b and c value for a b3950 thermistor table and the b value went up as well.
-
@veti said in Confusion about Semitec 104GT-2 B value in documentation:
i calculated the b and c value for a b3950 thermistor table and the b value went up as well.
Can you confirm that when you include a C value, the B value increases (which is contradictory to the statement in the Wiki)? I think we can all understand that when the B value is quoted for 25 deg C, then a higher value will be needed for around 200 deg C. The confusion arises from the inclusion of a C value as well as a B value, where the Wiki indicates in words that the B value should be lower, yet the example given shows a higher value is used.
-
using this table
https://www.makeralot.com/download/Reprap-Hotend-Thermistor-NTC-3950-100K.pdf
using 25 and 50 gives = Beta 3948 K
using 25 180 and 220 gives = R25: 100000 Ω β: 5071 K C : 1.793806e-7 -
@veti You haven't directly answered the question but from the numbers you've quoted, I'll take it that the words in the Wiki are incorrect and that when using a C value, the B value increases, rather than decreases as stated.
-
@bot said in Confusion about Semitec 104GT-2 B value in documentation:
However, here, you can find the following quote:
For greater accuracy, use a C parameter as well (note, the correct B value to use will be lower with a C parameter than without one).
4725 is clearly higher than 4388, but it is stated that with a C parameter the B value will be LOWER, not higher.
The note was wrong so I have corrected it. Thanks for pointing this out.
-
Excellent thank you everyone for the help.