Measuring device

1. A measuring device for measuring a physical variable with:

a converter configured to convert an input variable present at a measurement input into a measurement signal and to provide the same as an output variable;

a processing unit configured to process the output variable of the converter; and

a signal generator, configured to generate a test signal on a basis of a specification, wherein the test signal corresponds to an output variable of the converter and an input variable of the converter corresponding to the specification;

wherein the processing unit is configured to be connected, via a switching element, either to the converter or to the signal generator.

2. The measuring device of claim 1 , wherein the measuring device is configured to measure an electrical variable.

3. The measuring device of claim 2 , wherein the measuring device has six measurement inputs and is configured to measure a voltage and a current of a three-phase line, respectively, and wherein the signal generator is configured to generate six corresponding test signals.

4. The measuring device of claim 1 , wherein the measuring device is configured to be connected to a computer system and is configured to receive the specification for the test signal from the computer system.

5. The measuring device of claim 1 , wherein the specification comprises a phase shift, a frequency, a harmonic, an effective value, or a combination thereof, and wherein the signal generator is configured to generate the test signal on the basis of at least one of these parameters.

6. The measuring device of claim 1 , wherein the switching element comprises an electronic switch and the measuring device is configured to switch the switching element as a function of a control signal.

7. The measuring device of claim 6 , wherein the measuring device is configured to query a security feature comprising a password, an electronic identifier, or a combination thereof, to switch the switching element.

8. The measuring device of claim 1 , wherein the measuring device is configured to communicate via a Modbus-interface and to receive the specification via the Modbus-interface.

9. The measuring device of claim 1 , wherein the measuring device comprises:

an output interface and the processing unit is configured to output the processed output variable via the output interface.

10. The measuring device of claim 1 , wherein the switching element comprises an electronic switch in a microcontroller or a transistor.

11. A method for testing a measuring device for measuring a physical variable, the measuring device comprising a converter configured to convert an input variable present at a measurement input into a measurement signal and to provide the same as an output variable, the method comprising:

switching a switching element to connect a processing unit of the measuring device to a signal generator of the measuring device, wherein the signal generator is configured to generate a test signal on a basis of a specification, and wherein the test signal corresponds to an output variable of the converter and an input variable of the converter corresponding to the specification;

receiving the specification for the test signal at a control input of the measuring device;

outputting the test signal by the signal generator based on the specification to the processing unit; and

processing the output test signal by the processing unit.

12. The method of claim 11 , further comprising:

outputting the processed test signal via an output interface of the measuring device.

13. The method of claim 11 , wherein outputting the test signal comprises outputting an indication that the output is based on a test signal.

14. The method of claim 11 , wherein a security query is performed before switching the switching element, and wherein the switching element is switched to the signal generator based at least in part on a result of the security query being positive.

15. The method of claim 11 , wherein a display for displaying a switching position of the switching element is output when the switching element connects the signal generator to the processing unit.

16. The method of claim 11 , wherein the specification comprises a change in a parameter to represent an erroneous signal.

17. The measuring device of claim 1 , wherein the measuring device has two measurement inputs and is configured to measure a voltage and a current of a single-phase line, respectively, and wherein the signal generator is configured to generate two corresponding test signals.

18. The measuring device of claim 10 , wherein the transistor comprises a metal-oxide-semiconductor field-effect transistor (MOSFET) or a bipolar transistor.

19. The method of claim 11 , wherein receiving the specification comprises receiving the specification via a Modbus-interface.

20. The method of claim 16 , wherein the parameter comprises a phase shift, a frequency, a harmonic, an effective value, or a combination thereof.

21. A method for testing a measuring device comprising:

switching a switching element to connect a processing unit of the measuring device to a signal generator of the measuring device, wherein the signal generator is configured to generate a test signal on a basis of a specification;

receiving the specification for the test signal at a control input of the measuring device;

outputting the test signal by the signal generator based on the specification to the processing unit; and

processing the output test signal by the processing unit,

wherein a security query is performed before switching the switching element, and wherein the switching element is switched to the signal generator based at least in part on a result of the security query being positive.