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PT100

Started by alesbedac, Feb 21 2014 06:49 PM

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#1 alesbedac

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Posted 21 February 2014 - 06:49 PM

Hi All,

 

i am trying to get working PT100 sensor on Analog inputs.

3V3 is connected to one wire and second wire is connected to the analog input.

But the incoming value is not logical for me (0,53xxxxx) ..Is there abnybody who wants to help me.

 

I feel the wiring is not good do you want to help me please ?


#2 CW2

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Posted 22 February 2014 - 09:20 PM

Short answer: the PT100 is a resistive sensor, so you cannot connect it directly to an analog input.   Long answer: You'd have to use at least a voltage divider circuit, so you can measure the voltage drop over the sensor and make sure to use low current - usually up to [only] 1 mA, to prevent sensor damage and also reduce self-heating. PT100 is a precision sensor and getting accurate measurements require non-trivial circuits - for example, PT100 has about 20 ? difference in temperature range 0 - 50°C, which at 1 mA translates to 20 mV; also the parameters of microcontroller's ADC has to be considered. I'd recommend you to do some more research and have a look at articles like PT100 sensor - help a beginner? or Can't get a precise reading with PT100 temperature sensor. You might end up with the bridge configuration plus op-amps, or a specialized IC...


#3 alesbedac

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Posted 26 February 2014 - 03:38 PM

Short answer: the PT100 is a resistive sensor, so you cannot connect it directly to an analog input.   Long answer: You'd have to use at least a voltage divider circuit, so you can measure the voltage drop over the sensor and make sure to use low current - usually up to [only] 1 mA, to prevent sensor damage and also reduce self-heating. PT100 is a precision sensor and getting accurate measurements require non-trivial circuits - for example, PT100 has about 20 ? difference in temperature range 0 - 50°C, which at 1 mA translates to 20 mV; also the parameters of microcontroller's ADC has to be considered. I'd recommend you to do some more research and have a look at articles like PT100 sensor - help a beginner? or Can't get a precise reading with PT100 temperature sensor. You might end up with the bridge configuration plus op-amps, or a specialized IC...

 

thanks for very cool answer....i will go for investigate the URLs...


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