100 ohm ptc reading

[temtronic]

You need to post what RANGE of temperature you expect to use it for.
It's NOT designed for say, home thermostat controller.

Jay

[Ttelmah]

You need to understand these are not at all like normal NTC thermistors.
These are designed to just do the job of switching things off when they
overheat. So the response curve, is very flat below this, then rises sharply
at the switching temperature. As such making a measurement is going to
be awkward, and inaccurate. Even a 'normal' thermistor has quite an
awkward curve to deal with, but at least is is a reasonably gentle curve.
The maths in the standard thermistor code is designed to handle the NTC
curve, not the PTC curve.

The quoted response is around:

[MCUprogrammer]

How to read a log chart. How is the value 3000000 obtained in the 70 C and 130 C graph in the data network of the PTC sensor. Does anyone knows?
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[MCUprogrammer]

I will limit the current according to the resistor value I read. I want to print the temperature equivalent in the resistor I read. Yes I know. PTCs are used for protection circuits, not temperature measurement. But I will do so. I will only print the temperature corresponding to the resistance value I read.
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[temtronic]

I think you're confused how he charts/graphs are laid out.
there are 3 sensors per graph
The first graph(TPT1006-N) has your 'Tsense = 70*C' sensor,dotted line.
@70*C it's about 400r, @130*C it's 3Mohms

you can make a table of *C vs resistance using the graph. It is 'rough', NOT accurate and NOT linear.


Jay

[MCUprogrammer]

thank you mr jay.
what about ex_sk_temp_thermistor used in example
tempf = (float)(thermistor_convert(adc))/10.0;
Why are we doing the "/10.0" at the end of this code. Also, if we are going to do the conversion to celsius, will we do "/10.0"?
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[temtronic]

I don't have that example program ( I have older compiler version...) but did read that the thermistor_convert function returns a value to 2 decimal points ( ie: 98.62 )

the /10 would make that value 98.6 perhaps that's what the programmer sends to his display device ? There is a hardware cost to show more digits,both physical and software costs.

How many 'decimal points' depends on application. For me , I don't need to know it's 86.123456 *F outside, 86 *F is fine... well too hot for me,really .

Jay

[MCUprogrammer]

I am using version 5.105. I thought it was specific to converting that value to Fahrenheit.
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[temtronic]

yes, that function converts the ADC reading into *F based upon the data you supply for the RTD sensor.
If you wanted *C, simply take the function result (*F value) and convert to *C.