Can not find Model/Value of Thermistor.

[nmbb]

Machine: Autoclave.
Brand/Model: SANYO MLS-3780
Manual: (Sorry search option not working on this PDF)



Hello guys, this autoclave running with 2 thermistors already connected TH1 and TH3(on CN1,CN2 sockets). One for the water temperture and second one for chamber temperature. But there is another emtpy socket for optional third thermistor CN2 wich is for TH2 for object temperature. I wanna add the third thermistor TH2 to CN2 socket. But i can't figure what model/brand/value i need to use. In manual document, there is no info about TH1 and TH3 model number it says;







The only data in manual document is thermistor temperature/reference resistance chart;






According to this chart, if im reading correct, on room temperature 25c (Centigrade) TH1/TH3 value sohuld be 1390KOhms. So i go to mouser.com to check all brand thermistors and check bunch of thermistor manuals and can not find any thermistor matching 1390K ohm at 25C.


Also for your info here is the circuit diagram area about TH1,TH3,TH2(optional);






You guys can help me about finding what brand or value thermistor i need to use for TH2? Actually i want to find exact Model thermistor as same with TH1 and TH3. if i can find the exact brand thermistor i would be way happy.


And for your info, in the setting menu of the machine, there is thermistor calibration option. So it looks like i can use closer value thermistor and calibrate it. But its my second option. I want exact brand first.


THANKS FOR READING! And i would be greatfull if you can help me.

Regards..

[petehall347]

Re: Can not find Model/Value of Thermistor.

is the rest of the circuit actually there for the intended thermistor ?

[redwire]

Re: Can not find Model/Value of Thermistor.

It's an oddball thermistor to have such a high resistance 1,390k ohms at the reference temp 25°C. That's used only for high resolution at high temperatures. Nobody really uses that high a value part. Any moisture gives high readings. The circuit has 5 range select transistors which seems overboard for accuracy.

I would measure an existing thermistor resistance at room temp to see if it's close to the table. Sometimes there's typos and things are way off.

Looking at Japanese NTC thermistor manufacturers, Semitec and Murata, TDK but nowadays that value is just not used. 1MEG is the highest I saw.
I calculate the beta would be around B=4650K. It's in a glass package I assume.
There is GE/Amphenol TH513J44G which is 1,388k at 25C but low B=4491K means the curve is out.

[nmbb]

Re: Can not find Model/Value of Thermistor.

It's an oddball thermistor to have such a high resistance 1,390k ohms at the reference temp 25°C. That's used only for high resolution at high temperatures. Nobody really uses that high a value part. Any moisture gives high readings. The circuit has 5 range select transistors which seems overboard for accuracy.

I would measure an existing thermistor resistance at room temp to see if it's close to the table. Sometimes there's typos and things are way off.

Looking at Japanese NTC thermistor manufacturers, Semitec and Murata, TDK but nowadays that value is just not used. 1MEG is the highest I saw.
I calculate the beta would be around B=4650K. It's in a glass package I assume.
There is GE/Amphenol TH513J44Gwhich is 1,388k at 25C but low B=4491K means the curve is out.

Thank you so much for reply. The thermistors in metal tube shield so i can not see what package it is. So this old thermistor is probably is 10MEG?

I'm gonna measure TH1 or TH3 resistance at 25C tomorrow. Btw, the autocalve does not show temperature under 20C, it says on LCD "Low Temperature" Maybe its just software ignores under 20C or maybe its about the termistor. Actually this machine needs to run accurate at 110 TO 130C. So could be software ignore, because under 60C is never neccesarry for any modes to run. I just want to add this detail, maybe helps.

And, if i use any thermistor like TH513J44G, B value causes problem? Or calibrating temperatures manually(Done by couple steps, 48C, 74C, 100C, 118C, 135C) service menu settings would be fine?

And i want to to add that, this machine is my own. I bought it for my mushroom cultivation, it was broken and i repair it. Works fantastic! To repair i have to read tens of times the service manual, and i had deep feelings about Japan Engineering every step when i work with it. Software and mechanics and all safety procedures, quality mechanical parts, logics, pcb,connections.. EVERYTHING is awesome, i always love Japanese devices, but its first time i own such a complicated device. To be honest, im feelimg a strong emotional bond with my baby. I love her.

[nmbb]

Re: Can not find Model/Value of Thermistor.

is the rest of the circuit actually there for the intended thermistor ?

You mean the circuit for TH2 compotents mounted on pcb? I guess, yes. Because, there is Object Temperature button on Front Panel, and its active, i mean i can press it and little LED turns on. If you want, i can unplug TH1 from socket (CN1) and connect it to TH2's (CN2)socket and check. Btw, i share the PDF on first post, whole circuit there.

[nmbb]

Re: Can not find Model/Value of Thermistor.

Update:

Ok guys, i just measure TH1 resistance at 60C, its 270K. Looks like chart is accurate. My multimeter is very cheap chinese yellow one. I assume there is some miss measure my ohm meter. So, looks like its gonna hard to find kind of old thermistor.

So if i use like 100K/300C max glass package thermistor which ppl use it on 3D Printers, and if i calibrate it on autoclave settings, do you think software can handle B value and lower resistances? Or becasue of complicated range select circuit i need to use closer value of 10MegOhm ish?

Waitin your replies, thank you!

[Per Hansson]

Re: Can not find Model/Value of Thermistor.

If you can calibrate the curve the thermistor redwire suggested is a good example.
It actually exists in a version with a beta value of 4599K which I think is the correct part: TH513F45GBSN
I calculated a beta value of 4583 from your datasheet print above so this is close enough.
In the part number "F45" F=Tolerance 1% and 45 is beta value in range 4500K to 4599K

https://www.newark.com/amphenol-adva...ded/dp/77Y5088

[nmbb]

Re: Can not find Model/Value of Thermistor.

If you can calibrate the curve the thermistor redwire suggested is a good example.
It actually exists in a version with a beta value of 4599K which I think is the correct part: TH513F45GBSN
I calculated a beta value of 4583 from your datasheet print above so this is close enough.
In the part number "F45" F=Tolerance 1% and 45 is beta value in range 4500K to 4599K

https://www.newark.com/amphenol-adva...ded/dp/77Y5088

Thank you so much. Redwire thank you too.