Hey Raza... Yea you are right, my meter give temperature like 150,151 but not like 150.1,150.2 so it is accurate up to one degree.
My Multimeter probe is of thermocouple and problem was that thermocouple response time is much faster then thermistor. I took three points at 25 degree, 100 degree and 250 degree. 25 degree was easy as the temperature at night was falling too slow and thermocouple stayed there for minutes.
hard part was to get resistance of thermistor at 100 and 250 degree centigrade. for that i used a small baking plate, put the plate over thermistor and thermocouple (tied together) and put iron on top (I modified the iron so it run continuously). At 100 degree temperature was still increasing but i put up the iron a little bit so temperature stayed there for a minute. same i did for 250 degree. Though my iron shape is totally changed from bottom, so you need a tough one.
Then i put these values in the following table
**broken link removed**
And now i have error maximum of 1 degree using S-H model. So i think its good.
Can't use surface touched base sensors because i am modifying my laminator so it should not touch the rollers.
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now i am thinking something else, an Idea to implement (if i got the time). Temperature calibrators are very expensive. so
I am going to use a small black metal box with a heater wire inside controlled by a Triac. The temperature of that box then can be controlled as well as maintained by Triac by triggering it at certain angles. What do you guys think?