Data carrier comprising strain gauge means
A data carrier ( 2 ) comprises a data circuit ( 4 ) arranged on a substrate ( 3 ) and data transmission unit ( 10 ) being connected to the data circuit ( 4 ). The data carrier ( 2 ) further comprises at least one strain gauge unit ( 7 ) being adapted to measure strains exerted on the substrate ( 3 ) and to transmit a deactivating signal (DE) to the data circuit ( 4 ) if the measured strains exceed a defined deactivating strain threshold. If the data circuit ( 4 ) receives the deactivating signal (DE), the data circuit ( 4 ) interrupts a data exchange with an external data reader/writer ( 1 ) via the data transmission unit ( 10 ).
1. A data carrier comprising a data circuit arranged on a substrate and data transmission means being connected to the data circuit wherein the data carrier comprises at least one strain gauge means being adapted to measure strains exerted on the substrate and to transmit a deactivating signal to the data circuit if the measured strains exceed a defined deactivating strain threshold, the data circuit being adapted to interrupt a data exchange with an external data reader/writer via the data transmission means, if the data circuit receives the deactivating signal.
2. The data carrier as claimed in claim 1 , wherein the strain gauge means comprise at least one strain sensor arranged on or in the substrate and a strain evaluating circuit having a measuring input that is connected to the strain sensor, the strain sensor delivering a physical quantity that corresponds to the strains exerted on the substrate, and the strain evaluating circuit being adapted to compare the physical quantity delivered by the strain sensor with a threshold value of the physical quantity that corresponds to a deactivating strain threshold and to generate the deactivating signal if the physical quantity of the strain sensor exceeds the threshold value of the physical quantity.
3. The data carrier as claimed in claim 2 , wherein the at least one strain sensor comprises at least one electric resistor having a resistance value that varies with the strain exerted on the resistor.
4. The data carrier as claimed in claim 3 , wherein the electric resistor is configured as a poly resistor.
5. The data carrier as claimed in claim 3 , wherein the electric resistor is arranged on or in the substrate in a meandering configuration.
6. The data carrier according to claim 2 , wherein the at least one strain sensor is arranged in a peripheral region of the substrate.
7. The data carrier according to claim 2 , wherein the at least one strain sensor encompasses the data circuit at least partly.
8. The data carrier according to claim 3 , wherein the cross-sectional area and/or the meandering shape of the electric resistor is varied in different sections of the electric resistor.
9. The data carrier according to claim 2 , wherein at least a first strain sensor is arranged on an upper surface or embedded in an upper layer of the substrate and at least a second strain sensor is arranged on a lower surface or embedded in a lower layer of the substrate, preferably the first and second strain sensors being arranged in alignment with each other on opposite surfaces or layers, and a difference between output signals of the first and second strain sensors being used to evaluate the strain exerted on the substrate.
10. The data carrier according to claim 2 , wherein a plurality of strain sensors are provided, the output signals of the plurality of strain sensors are evaluated independently, and optionally different deactivating strain thresholds are defined for the strain sensors.
11. The data carrier according to claim 3 , wherein the electrical resistor is switched into a bridge circuit, the bridge circuit being adapted to measure the resistance of the electrical resistor.
12. The data carrier according to claim 9 , wherein the first and the second strain sensors are configured as strain-dependent resistors which are switched into a bridge circuit, the bridge circuit being adapted to measure the difference between the resistance values of the two strain-dependent resistors.
13. The data carrier according to claim 1 , wherein the interruption of data exchange via the data transmission means is maintained as long as the deactivating signal occurs.
14. The data carrier according to claim 1 , wherein a temporary occurrence of the deactivating signal is permanently stored in the data circuit.
15. The data carrier according to claim 1 , wherein upon the temporary occurrence of the deactivating signal, the data exchange between the data carrier and the external data reader/writer is permanently interrupted.
16. The data carrier according to claim 1 , wherein the strain gauge means are adapted to transmit a damage signal to the data circuit if the measured strains exceed a damaging strain threshold, the data circuit being adapted to permanently interrupt the data exchange with the external reader/writer via the data transmission means if the damage signal is received by the data circuit.
17. The data carrier according to claim 2 , wherein temperature-dependent changes of the output signal of the strain sensor ( 6 ) are monitored and logged in the data circuit.