....Background.... Yesterday when I was printing, I found that the temperature reading jumps from 258 to 270, with nothing in between. (I know 258 is very inaccurate, it couldn't be that hot) Later I found that the table generated by ./createTemperatureLookup.py --r0=6360 --t0=100 --r1=0 --r2=4700 --beta=3990 --max-adc=1023 Just do not give enough resolution at the first band. Now I solder a 3k ohm in parallel with the 4.7k, making r2=1818. Much better resolution. Now I fire up my heater, no matter what it could only reach 215! Heat is losing way too fast. Previously the upper limit is 285. I didn't change any other beta value. (The beta is just comes from the datasheet). ....Ask.... Oh well so now I fully understand what it means "...Although the properties of ABS are fixed, it’s hard to get a dead-on calibration of the thermistor..." [blog.thingiverse.com] Perhaps I should go and buy a IR thermometer gun, I just saw one selling at ~USD20 (RMB 120). Though I just wonder, without that, what does everything one use to tune their thermistor? Or people just go ahead and use thermocouple instead? https://reprap.org/forum/read.php?14,27172,27172#msg-27172 Sat, 13 Jun 2026 13:59:23 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?14,27172,27423#msg-27423 https://reprap.org/forum/read.php?14,27172,27423#msg-27423
I think both work equally well unless you want to go above 300C.]]> nophead Mechanics Fri, 11 Sep 2009 12:28:23 -0400 https://reprap.org/forum/read.php?14,27172,27327#msg-27327 https://reprap.org/forum/read.php?14,27172,27327#msg-27327
I think there are something we can do in the firmware to combat with loss thermocouple. Say if the temperature wasn't raised for X degrees C in Y seconds, something is going wrong (a loose thermistor/thermocouple) and hence e-stop should be triggered.]]> sam0737 Mechanics Wed, 09 Sep 2009 02:07:06 -0400 https://reprap.org/forum/read.php?14,27172,27299#msg-27299 https://reprap.org/forum/read.php?14,27172,27299#msg-27299
[builders.reprap.org]

Your all-metal extruder won't fail like that, but a malfunctioning heater could possibly burn some feedstock.

Wade]]> Wade Mechanics Tue, 08 Sep 2009 15:53:34 -0400 https://reprap.org/forum/read.php?14,27172,27296#msg-27296 https://reprap.org/forum/read.php?14,27172,27296#msg-27296
I spent 15 minutes on the noise though. I forgot the motor is grounded to my toolhead, and the thermalcouple is not isolated. Then when I spins up the motor, the measured temperature jumps -50 to +50 around the real temperature.
It's solved by putting a slice of Kapton tape over the measuring point.

With a thermistor running side by side, I can see how much different there were...]]> sam0737 Mechanics Tue, 08 Sep 2009 15:36:42 -0400 https://reprap.org/forum/read.php?14,27172,27203#msg-27203 https://reprap.org/forum/read.php?14,27172,27203#msg-27203 What is the difference between AD595CQ (Cerdip) and AD595CD (TO-116)?

They are just the same footprint, with one of them have a metal plate over it. Functionally what are the differences? Which one is better?

While I am waiting for the thermocouple and chip, I milled my first usable PCB!
[picasaweb.google.com]#
(Surely it could be faster and easier with wire-wrap board, but I don't have one now)]]> sam0737 Mechanics Sun, 06 Sep 2009 13:51:00 -0400 https://reprap.org/forum/read.php?14,27172,27198#msg-27198 https://reprap.org/forum/read.php?14,27172,27198#msg-27198
Now I am going to buy a thermocouple-K and AD595 and see how it goes.]]> sam0737 Mechanics Sun, 06 Sep 2009 10:55:23 -0400 https://reprap.org/forum/read.php?14,27172,27175#msg-27175 https://reprap.org/forum/read.php?14,27172,27175#msg-27175
I've got a thermocouple for my multimeter that I use to check things, but I also just use thermocouples on my extruder. I didn't want to mess with temperature calibrations, especially since extruders are fairly sensitive to small changes in temperature.

One thing to check though, is noise. I find that when I have grounding problems anywhere between the thermocouple and the PC, my temperature readings start jumping around by 20 or 40 deg C. When everything is good, the noise is less than 1 deg C.

Wade]]> Wade Mechanics Sun, 06 Sep 2009 03:21:16 -0400 https://reprap.org/forum/read.php?14,27172,27174#msg-27174 https://reprap.org/forum/read.php?14,27172,27174#msg-27174
There is a simple kit, which you can pretty much free form anyways on veroboard, from MakerBot.
I haven't got my machine up and running yet so its just an idea.]]> Grogyan Mechanics Sun, 06 Sep 2009 03:16:54 -0400 https://reprap.org/forum/read.php?14,27172,27172#msg-27172 https://reprap.org/forum/read.php?14,27172,27172#msg-27172 ....Background....

Yesterday when I was printing, I found that the temperature reading jumps from 258 to 270, with nothing in between. (I know 258 is very inaccurate, it couldn't be that hot)

Later I found that the table generated by
./createTemperatureLookup.py --r0=6360 --t0=100 --r1=0 --r2=4700 --beta=3990 --max-adc=1023

Just do not give enough resolution at the first band.

Now I solder a 3k ohm in parallel with the 4.7k, making r2=1818.

Much better resolution.

Now I fire up my heater, no matter what it could only reach 215! Heat is losing way too fast. Previously the upper limit is 285.

I didn't change any other beta value. (The beta is just comes from the datasheet).

....Ask....

Oh well so now I fully understand what it means "...Although the properties of ABS are fixed, it’s hard to get a dead-on calibration of the thermistor..." [blog.thingiverse.com]

Perhaps I should go and buy a IR thermometer gun, I just saw one selling at ~USD20 (RMB 120). Though I just wonder, without that, what does everything one use to tune their thermistor?

Or people just go ahead and use thermocouple instead?]]> sam0737 Mechanics Sun, 06 Sep 2009 02:36:35 -0400