# Why thermocouple is an active transducer?

**URL:** <https://forumautomation.com/t/why-thermocouple-is-an-active-transducer/4176>\
**Category:** Temperature Measurement\
**Created:** [July 21, 2018, 6:09am UTC](https://forumautomation.com/t/why-thermocouple-is-an-active-transducer/4176 "2018-07-21T06:09:57Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![areejsidhik](https://forumautomation.com/letter_avatar_proxy/v4/letter/a/ee59a6/32.png) [@areejsidhik](https://forumautomation.com/u/areejsidhik)\
**Post date:** [July 21, 2018, 6:09am UTC](https://forumautomation.com/t/why-thermocouple-is-an-active-transducer/4176/1 "2018-07-21T06:09:57Z")

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The output of the [thermocouple](https://forumautomation.com/search?q=thermocouple%20) is voltage difference on its terminals that is proportional to the corresponding temperature .But when we look in to the case of passive transducers or sensors the output will be change in some passive electrical quantity such as capacitance ,resistance or inductance

Another way to find an active and passive device is , **if something requires power supply to operate it’s active otherwise it’s passive**

_ **Example for active transducers:Piezoelectric Type,thermopile,LVDT** __ **Example for passive transducers:RTD,Resistance Hygrometer,resistance thermometer** _