There is provided a device for monitoring sterilization of a material with steam comprising at least one layer, having incorporated therein an isomeric indicator, capable of undergoing at least one color change and optionally a controller for said indicator capable of influencing the time and temperature required for said color change when contact with steam. The base has an electronic card holder for holding an electronic card. A temperature sensor senses temperature and proves a temperature signal to a microcontroller. The multiplier modulates the transmission signal output from the filter.