A probe comprises a resistive element configured to be brought into thermal contact with an entity to be sensed. A measurement system applies a plurality of heating pulses to the resistive element by driving an electrical current through the resistive in element and measures an electrical response of the resistive element to the heating pulses in order to determine information about either or both of the composition and state of the entity. The measurement system generates an output signal using the measured electrical response, wherein the output signal is generated by progressively offsetting the measured electrical response such that, in the event of an average temperature of the resistive element changing between different heating pulses due to a drift in the average temperature of a portion of the entity being sensed, a variance over the plurality of heating pulses of a value of the output signal at a predetermined common reference point within each heating pulse is reduced.