The barretter provides a linear relatonship between power absorbed and its resistance, but it is rather fragile and will not withstand electrical overloads well. The thermistor is more robu and sensitive, but the resistance change is not linearly related ti the temperature or, therefore, the power absorbed (see Fig 3.1) The MWT530 therefore uses a thermistor-type bolometer in way that its non-linearity does not matter.