Resonance tag with temperature sensor
A temperature-history sensor includes a resonance circuit composed of at least a capacitor and a coil. The temperature-history sensor has a display for indicating a predetermined set temperature of the temperature-history sensor. The capacitor has at least a thermofusion material between electrodes of the capacitor, and the melting point of the thermofusion material is in the region of the set temperature.
1. A temperature-history sensor comprising:
a resonance circuit comprising:
a coil;
a first capacitor; and
a second capacitor,
wherein a change of an effective dielectric constant of each of the first capacitor and the second capacitor changes a resonance characteristic of the resonance circuit,
wherein each of the first capacitor and the second capacitor includes a pair of electrodes, wherein the electrodes of each pair face each other and are separate from each other via a gap,
wherein a first material becomes fluidized at a first temperature and moves into the gap or outside of the gap of the first capacitor, so that the effective dielectric constant of the first capacitor is changed, and as a result, the resonance circuit has a first resonance characteristic, and
wherein a second material becomes fluidized at a second temperature which is higher than the first temperature and moves into the gap or outside of the gap of the second capacitor, so that the effective dielectric constant of the second capacitor is changed, and as a result, the resonance circuit has a second resonance characteristic.