Hybrid voltage supply for a measuring instrument

A measuring system, comprising:

• an electronics, comprising:
• a load circuit having a circuit input, at least one microprocessor, and at least one linear voltage regulator;
• a power supply circuit formed by one or more direct voltage converters, the power supply circuit including a circuit input, a first circuit output, a second circuit output, and a rechargeable electrical energy storer having a nominal capacity and completely charged providing a cell voltage of voltage level of nominal value equals or greater than 3 V (volt), wherein the energy storer is electrically connected with the second circuit output of the power supply circuit in such a manner that the cell voltage of the energy storer or a voltage proportional thereto lies on the second circuit output;
• and
• a protection circuit including a first circuit input, a second circuit input, and a circuit output,
• wherein the circuit input of the load circuit is at least at times electrically connected with the first circuit output of the power supply circuit in such a manner that in the case of an output voltage on the first circuit output of the power supply circuit an electrical current flow is enabled, from the first circuit output to the circuit input and/or an energy flow from the power supply circuit to the load circuit is enabled,
• wherein the circuit output of the protection circuit is electrically connected with the circuit input of the power supply circuit,
• wherein the first circuit input of the protection circuit is adapted to be electrically connected with a circuit output of an external energy supply providing a supply voltage for the electronics, and wherein the second circuit input of the protection circuit is electrically connected with the second circuit output of the power supply circuit, in such a manner that an input voltage applied to the second circuit input corresponds to the cell voltage provided by the energy storer,
• wherein both the power supply circuit as well as also the protection circuit have, in each case, at least two operating modes,
• wherein in a first operating mode of the power supply circuit its energy storer is switched to the first circuit output in such a manner that the cell voltage provided by the energy storer or a voltage proportional thereto is applied to the first circuit output as a first output voltage,
• wherein in a second operating mode of the power supply circuit, its circuit input is switched to its first circuit output,
• wherein in a first operating mode of the protection circuit, its first circuit input is switched to its circuit output
• wherein in a second operating mode of the protection circuit its first circuit input and its circuit output are electrically isolated from one another, and
• wherein the protection circuit is adapted in the first operating mode to monitor the cell voltage applied to the second circuit input to determine whether its voltage level has exceeded a predetermined maximum value lying above its nominal value and, in given cases, automatically to deactivate its first operating mode or automatically to switch from its first operating mode into its second operating mode;
• and
• electrically coupled with the electronics, a measuring transducer, which is adapted to register at least one physical or chemical measured variable and to transduce the registered measured variable into at least one measurement signal representing the measured variable.