Why does pt 100 has three terminals while thermocouples like type k has two terminals only?

pt100 لها ثلاث اطراف وذلك لانها تقيس الحراره عن طريق التغير فى المقاومه وبالتالى لابد من اخد طرف ثالث كمرجع لقيمه المقاومه الناتجه من الاسلاك حتى تكون المقاومه الناتجه هى فقط من ناتج الحراره وليس من ناتج الحراره + مقاومه الاسلاك

انما type k وباقى انواع الثرموكابل طرفان فقط لانه يقيس الحراره عن طريق التغير فى الفولت حيث انه عند مرور حراره يتولد تيار بالمللى فولت وعن طريق جدول يمكن معرفه مقدار الحراره المكافئه للفولت الناتج

RTDand TC were used to measure temprature. PT100 gives100 Ohm at0C temp. Third wire in RTD is used to compensate/minimise the wire lenght resistance. TC works on Different , in it the voltage generated between the measuring end and guage end. so only two wires used.

PT100 refers to a100 ohm (at0 C) platinum resistance temperature detector RTD

Third wire used to compensate the wire lenght resistance

A thermocouple is a welded junction of two different metals. It produces a small voltage that is a function of temperature. Often thermocouples are used in pairs such as copper and constantan with the constantan wires connected together

الفرق اللى اعرفه ان ال pt100 بتقيس لحد400 درجه سليزيوس انما الtype k بيقيس لحد1200 تقريبا

cause pt100 measure by resistance so it should there a refrence

right answer for muhammed hafez

You only assume that the two current carrying leads have the same volt-drop. The third sense wire characteristics don't matter.The third wire senses the volt-drop of one of the current carrying wires, and the calculation bases its assumption that the other, unsensed volt-drop is equal to the first. Once the voltage across the RTD is known, Ohm's Law takes over.

PT100 refers to a100 ohm (at0 C) platinum resistance temperature detector RTD

          Third wire used to compensate the wire lenght resistance

لانه بيقيس عن طريق المقاومه

because pt100 measures the tempreature by resistance