NTC Thermistor substitution possible?

[bletchmonster]

Hello all, one for the electronickryists. We have an ageing ISE10 washing machine that has sailed past it's 10 year guararantee without issue! But now it's attention seeking. It doesn't seem to be heating the water.
The heating element seems to test out ok, but the tempreture sensor thermistor does not, I'm getting a resistance of 60 ohms, the book lists it at 6.1 to 3.8 K Ohms ( this is definitely a teeny bit of knowledge is dangerous situation, but that goes for most of what I do).
It's an Asko part that seems to have a six week lead time on it, so I was wondering if it's possible to substitute a thermistor of similar values. It's simply held against the outside of the drum so the simplest of bodging can sort the mounting, it's the numbers I can't deal with. I was wondering if anyone can guide me , tell me if it's even possible if only for a temporary bodge/ experiment? I (think)I have attached a pic of the part and the asko manuals resistance values for the thermistor.
Thanks, Ed

 

[Seadog]

I'd give it a go with whatever you can find.
By comparing the resistance values against temperature you'll be able to gauge at which point it'll cut out.

 

[bletchmonster]

Thanks Seadog, that's where I'm struggling, correlating those nice simple values to what I can find. I need a thermistors for dummies guide

 

[Seadog]

Do you have the original component number?
If so, the spec sheet should provide values. Or that what you've already listed?
Edit: I assume that theyvalues from the machine manual?
It shouldn't be difficult to find something with similar values, as long as it present a few kΩ to start with it's going to work after some fashion.

 

[voipio]

The "calibration curve" of NTCs will depend on the recipe used to make the NTC material. NTCs can have their resistance values given at 20 or 25degC, so that may be a starting point, but they are also more often rated using so-called beta values (or B-value). Based on the resistances at 10 and 30 degC, I make the B-value for the NTC data given in the resistance table to be 3881, so look for one having a value close to this. A B-value of 3950 should be close enough. There's a handy calculator here, for you to have a go yourself:

NTC Thermistor Beta

The way resistance of a thermistor decreases is related to a constant known in the thermistor industry as beta (β). Learn how to calculate Beta.

www.ametherm.com

 

[bletchmonster]

Do you have the original component number?
If so, the spec sheet should provide values. Or that what you've already listed?
Edit: I assume that theyvalues from the machine manual?
It shouldn't be difficult to find something with similar values, as long as it present a few kΩ to start with it's going to work after some fashion.

The spec sheet I've given is for a very similar Asko machine. I think Asko built the very short lived Ise10 machines. A lot of parts are interchangable between the two brands.

 

[bletchmonster]

The "calibration curve" of NTCs will depend to some extent on the recipe used to make the NTC material. NTCs can have their have resistance values given at 20 or 25degC, so that may be a starting point, but they are also more often rated using so-called beta values (or B-value). Based on the resistances at 10 and 30 degC, I make the B-value for the NTC data given in the resistance table to be 3881, so look for one having a value close to this. A B-value of 3950 should be close enough. There's a handy calculator here, for you to have a go yourself:

NTC Thermistor Beta

The way resistance of a thermistor decreases is related to a constant known in the thermistor industry as beta (β). Learn how to calculate Beta.

www.ametherm.com

Thank you, I'll pursue that.

 

[voipio]

Look for devices with a B-value of 3950, and a resistance at 25degC of 5kOhms. Sorry, didn't make it clear in my previous posting. Busy doing other things at the time.

 

[bletchmonster]

Look for devices with a B-value of 3950, and a resistance at 25degC of 5kOhms. Sorry, didn't make it clear in my previous posting. Busy doing other things at the time.

Thank you again, your intial B value vastly improved my understanding of what I was looking at , That's really helped

 

[bletchmonster]

Update, I ordered a couple of thermistors based on @viopio advise, superglued one to the back of the defunct one and hey presto the washer is heating the water again for, I suspect, the first time in ages.
If the new one fails I will look into encapsulating the next one in some sort of heat transfer resin.
I wanted to establish the thermistor would cure the issue before going to town on it.
Thanks again for the advise, a few pennies worth of a component has saved many pounds and a six week wait.
It would be good to have a forum data base of nla/expensive part substitution success, but God knows how it could be catalogued to be of any use.