Contact thermometers differ from regular thermometers in that they are connected to a heating coil, and are hence able to both sense and control the current temperature. In doing so, they allow experiments to be performed under a constant temperature. Contact thermometers work using a negative feedback loop: once the desired temperature has been reached, the heating coil is deactivated; when the temperature falls, the heating coil is reactivated.
Os termómetros de contacto diferéncianse dos termómentros habituais en que se conectan a un cable que se quenta e que, polo tanto, permiten percibir e cotrolar a temperatura. Con iso permiten poder realizar experimentos baixo condicións de temperatura constantes. Os termómetros de contacto funcionan mediante un mecanismo de retroalimentación negativa: unha vez que se acadou a temperatura desexada déixase de quentar o cable; cando a temperatura baixa, reactívase o mecanismo que quenta o cable.