The invention relates to an electronic device having an electronic unit having an energy connection for feeding the electrical energy required for operating the electronic unit and having an energy storage unit which supplies the electronic unit with the electrical energy required for the operation thereof by means of an electrical supply current. The invention further relates to a method for operating an electronic device which has an electronic unit having an energy connection and an energy storage unit, wherein an electrical energy required for operating the electronic unit is provided by the energy storage unit by means of an electrical supply current.

Such electronic devices and the operating methods thereof are known in various embodiments. Most of the currently commonplace electrical appliances are constructed in such a manner and are supplied with electrical energy and operated in a battery-supported or accumulator-supported manner. In this instance, the battery and the accumulator are possible embodiments of the energy storage unit mentioned. An example of such an electronic device is the energy meter according to EP 3 855 147 AL The energy storage unit which is provided for supplying with electrical energy has to be maintained from time to time, wherein depending on the embodiment as a battery or as an accumulator a replacement or a charging is carried out. In order to keep the complexity low, on the one hand, this maintenance operation should not be carried out too early and, in order to prevent an operational failure of the electronic appliance, on the other hand, it should not be carried out too late. Previously, this maintenance time is established, for example, from an estimation of the consumption of electrical supply energy. Since it is based on estimated values, a maintenance time which is established in this manner is not particularly precise so that the maintenance is often carried out too early to ensure seamless operation/service.

An object of the invention is therefore to provide an electronic device of the type set out in the introduction having improved properties compared with the prior art.

In order to achieve this objective, an electronic device according to the features of patent claim 1 is set out. The electronic device according to the invention has a buffer capacitor which is connected to the energy connection electrically parallel with the electronic unit, a current measurement location for detecting the electrical supply current, wherein the current measurement location is arranged between an output connection of the energy storage unit and the buffer capacitor, and a control/evaluation unit which is configured to establish from the detected electrical supply current an electrical charge quantity taken from the energy storage unit and a residual electrical charge quantity which is currently still stored in the energy storage unit.

The energy storage unit is in particular a battery or an accumulator. The electrical supply current which is discharged therefrom in order to supply energy to the electronic unit is in particular a direct current. The energy connection of the electronic unit to which the electrical supply energy is fed, may be an external connection, but also an internal connection without accessibility from the outer side. The term “energy connection” is in this regard intended to be understood in general terms. Furthermore, the electronic unit can generally be understood to be a consumer, requiring electrical energy for its own operation. The control/evaluation unit which is in particular connected to the current measurement location may preferably be a (for example, integral) component of the electronic unit. A particularly simple and cost- effective construction which at the same time has a high level of efficiency is thereby produced.

It has been recognised that the in particular advantageous remaining availability time period of the energy storage unit, with a battery its remaining service-life and with an accumulator its remaining time period until recharging is required, can be determined in a much more precise manner when not based on an estimation, but instead on measurement values of the electrical supply current actually discharged from the energy storage unit. From the quantity of residual charge which is currently still stored in the energy storage unit and which is established based on these measurement values, in particular the remaining availability time period of the energy storage unit, that is to say, in particular the remaining period of time until the time from which the energy storage unit will no longer provide sufficient electrical energy to supply the electronic unit can be determined. In this case, this determination is preferably a calculation for the implementation of which the control/evaluation unit is also in particular configured and in the context of which, for example, the established residual electrical charge quantity still currently stored in the energy storage unit is divided by a typical value of the supply current, for example, a supply current mean value or a supply current empirical value. This determination of the remaining availability time period which is based in particular on measurements and calculations is considerably more precise than the estimations provided in known solutions.

The control/evaluation unit is in particular configured to determine the current quantity of residual charge Qi<( 1) via an evaluation, preferably a digital evaluation, of the formula relationship:

QRW = QO'QECO ⁼ Qo" f _tg lv(t)dt (1) where Qo is an initial charge quantity of the energy storage unit particularly stored in the control/evaluation unit, Qif t) is the previously taken charging quantity, t is the current time, to is the initial time from which the energy output from the energy storage unit is carried out, and Iv(t) is the electrical supply current at the respective time t. The detected electrical supply current Iv(t) is consequently involved in particular in the determination of the electrical charge quantity Qi ( 1) which is taken from the energy storage unit and which is then itself used to determine the remaining residual charge quantity Qi<(t) of the energy storage unit.

Furthermore, the control/evaluation unit is in particular configured to determine from the established residual electrical charge quantity Qi<(t) currently still stored in the energy storage unit a remaining availability time period of the energy storage unit, preferably to display it, and/or in particular to transmit it to another unit or device for further processing of this information.

The buffer capacitor is used for intermediate storage of the electrical energy with which the energy storage unit supplies the electronic unit. Load peaks of the electronic unit with brief high energy requirement are covered by the energy temporarily stored in the buffer capacitor. The energy temporarily stored in the buffer capacitor is rapidly made available to the electronic unit, whereby the buffer capacitor is also rapidly discharged. The recharging of the buffer capacitor is then carried out more slowly via the electrical supply current of the energy storage unit. Without a buffer capacitor, the temporary high supply current which occurs in the event of such a load peak could with a current detection carried out in particular only at different times be overlooked with the result that the quantity of charge taken from the energy storage unit involved with this supply current peak is also overlooked. The residual charge quantity and consequently the remaining availability time period are then also incorrectly established. This error source is prevented with the buffer capacitor since the recharging of the buffer capacitor after such a load peak is carried out significantly more slowly so that the recharging current (= supply current) originating from the energy storage unit is safely detected and accordingly also taken into account in the determination of the charge quantity taken from the energy storage unit. The buffer capacitor smooths the electrical supply current taken from the energy storage unit. Furthermore, it stabilises a consumer supply current which is applied to the electronic unit at the energy connection thereof. As a result of the smoothing mentioned, it is in particular sufficient for the electrical supply current not to be detected permanently, that is to say, not continuously, but instead only at different times in a preferably even relatively rough timeframe with a time spacing between two sequential measurements of, for example, up to several hours. The buffer capacitor has a capacitance value of in particular between 0.01 F and 100 F, preferably between 0.5 F and 5 F. A typical value is preferably approximately 0.5 F, for example, with an electronic unit having a low energy consumption, for example, when the electronic unit has a relatively energy-saving communication module, in particular a LoRa communication module, or at approximately 5 F, for example, with an electronic unit having high load peaks, for example, when the electronic unit has a communication module with an at least temporarily comparatively high energy requirement, in particular an Nb loT communication module. The abbreviation “LoRa” stands for “Long Range” and refers to a radio technology which enables a very power-saving and extensive data transmission. The abbreviation “Nb loT” stands for “Narrowband Internet of things” and also refers to a radio technology which is used, for example, with remotely controlled measurement or metering appliances, such as thermal or electrical consumption meters or flow meters. The Nb loT radio technology enables as a result of the good network coverage and building penetration the transmission of consumer data at regular intervals to a central server of the consumer or network operator. In this instance, these are small quantities of data which do not require broadband data networks.

Advantageous embodiments of the electronic device according to the invention will be appreciated from the features of the claims dependent on claim 1.

An embodiment is advantageous in which the current measurement location has an electrical current measurement resistor, wherein the current measurement resistor is arranged between a first electrical connection location of the output connection of the energy storage unit and the buffer capacitor. The detection of the electrical supply current by means of a current measurement resistor is simple to implement and nonetheless provides very reliable measurement results. In particular, the current measurement location further also has a voltage measurement unit which detects the voltage which drops over the current measurement resistor. The detected voltage value is a measurement for the relevant supply current which can be established by means of Ohm’s law with a known value of the current resistor from the detected voltage value. The current measurement resistor is in particular connected in series with respect to the inner resistor of the energy storage unit. Both resistors preferably form a voltage divider. The current measurement resistor has a resistance value of in particular between 10 Q and 1 kQ, preferably between 50 and 300 Q. A typical value is preferably approximately 100 Q. The current measurement resistor may be a standard resistor. Preferably, however, for example, when there are high demands with regard to the measurement prevision, it may also be a stable resistor whose resistance value in particular does not change with temperature and/or in particular does not change with time. Thus, the temperature coefficient thereof may advantageously be very low and in particular in the range between 5 ppm/K and 100 ppm/K/ A typical value is in particular 25 ppm/K.

According to another advantageous embodiment, the control/evaluation unit is configured to establish the quantity of residual electrical charge still stored in the energy storage unit in a cyclical manner at different establishment times which are spaced apart from each other by an averaging interval. The only cyclical establishment of the quantity of residual charge is energy-saving and nonetheless completely sufficient for the intended purpose. Updated information relating to the charge state of the energy storage unit is sufficient merely from time to time. The averaging interval may in this instance be located in particular within the time range between half a day and 14 days, preferably between a day and a week. For example, it may be half a day, a whole day, two days or also a week long. However, other (shorter or longer) averaging intervals are also possible in principle. If the electronic unit is constructed or operated in such a manner that it cyclically has a particularly high energy requirement (= load peak), for example, since it then transmits a radio signal in each case, it is advantageous for the averaging interval to be a multiple of the at least substantially constant and preferably known temporal load peak interval which is between two successive times at which the electronic unit has the mentioned high energy requirement. It is thereby ensured that in each averaging interval at least with regard to the known or predictable energy requirement there are approximately the same relationships.

According to another advantageous embodiment, the control/evaluation unit is configured to detect the electrical supply current in a cyclical manner at different detection times which are temporally spaced apart from each other by a measurement interval, and in particular from the values of the electrical supply current which are detected within each of the averaging intervals to determine a supply current mean value for the relevant averaging interval and from this to determine the quantity of electrical charge taken in this averaging interval. The only cyclical detection of the supply current is also energy-saving, in particular since compared with a continuous measurement the energy requirement for the detection of a measurement value occurs only significantly less often. The cyclical detection of the supply current advantageously enables a compromise between, on the one hand, measurement precision and, on the other hand, expenditure in terms of energy consumption and/or time, during which the electronic unit is in an active mode. The averaging of the values of the electrical supply current detected in an averaging interval brings about more reliable results. Exceptional values of the supply current, which are brought about, for example, by means of dismptive effects (for example, coupling of EMC errors) and which accordingly have no significance for the state of the energy storage unit, are as a result of the averaging not involved or involved only to a lesser extent in the results. In this regard, the averaging leads to an advantageous smoothing. The measurement interval is in particular shorter than the averaging interval. The averaging interval may in particular be greater by a three-digit factor than the measurement interval. In particular, the ratio of averaging interval to measurement interval is in the range between 100 and 1000. The averaging interval is preferably an integral multiple of the measurement interval. Per averaging interval, the same number of detections of the supply current are always in particular carried out, wherein this number corresponds to the integral multiple mentioned. A typical value of the ratio of averaging interval to measurement interval is 360. If the averaging interval is in this typical case, for example, a day, the measurement interval has a value of 240 seconds or 4 minutes. Furthermore, it is advantageous if there is always the same number of known or anticipatable load peak results, that is to say, events with a high energy requirement, such as, for example, radio events in each averaging interval. A falsification of the supply current mean value determined is thereby prevented, which would therefore otherwise stem from the fact that such a known or anticipatable load peak event could nonetheless randomly come to rest in one of two temporally successive averaging intervals.

According to another advantageous embodiment, the control/evaluation unit is configured to determine the supply current mean value for the relevant averaging interval in each case by means of a linear averaging, a root mean square averaging or a low-pass averaging. These averaging operations can be implemented in a simple manner.

According to another advantageous embodiment, the measurement interval is smaller than half of the product of the values of the buffer capacitor and a current measurement resistor of the current measurement location. This product is in particular the time constant of the RC member from the current measurement resistor and the buffer capacitor. With a measurement interval which is sized in such a manner, all the relevant supply current operations are detected. A high level of detection precision is thus achieved. In comparison, (significantly) longer measurement intervals could otherwise lead to a measurement not being carried out often enough and the exponential curve of the charging of the buffer capacitor no longer being approximated precisely enough.

According to another advantageous embodiment, a voltage measurement location for detecting an electrical storage supply voltage of the energy storage unit is connected to the output connection of the energy storage unit. The detection of the storage supply voltage may in this instance be able to be switched on and off. In particular, the voltage measurement location may have a voltage divider which is arranged parallel with the output connection of the energy storage unit and which can preferably be switched on and off and which is connected with a voltage divider resistor to a voltage measurement unit in order to detect the voltage which drops over this voltage divider resistor as a measurement for the storage supply voltage. This voltage measurement unit which is provided to detect the storage supply voltage may optionally but not necessarily be the same voltage measurement unit which is also used in the above-described advantageous embodiment of the current measurement by means of a current measurement resistor. Preferably, a switch may then be provided so that the voltage measurement unit is alternately available for both measurement applications. As a result of this optional double use of the voltage measurement unit, a particularly simple and cost-effective construction is produced. The information items obtained by means of the detection of the storage supply voltage can advantageously be used to control the findings obtained by the current detection relating to the remaining availability time period of the energy storage unit. Thus, the detected storage supply voltage allows additional statements relating to the current state or the actual quality of the energy storage unit. Thus, for example, the value of the internal resistor of the energy storage unit may change as a result of age and/or over time. In particular, it may increase which can then also be recognised by a changed measurement value of the detected storage supply voltage. In order to determine the internal resistance in the most precise manner possible, the control/evaluation unit is in particular configured to detect the storage supply voltage at a high load with a supply current of in particular at least 0.5 mA and at a low load with a supply current of in particular a maximum of 50 pA. The voltage detection is thus an additional monitoring of the energy storage unit, in particular the internal resistance thereof, and further enables an identification of whether the energy storage unit will potentially fail prematurely, for example, because it is defective, it is a used or incompletely charged energy storage unit, or more charge has already been taken from it than the evaluation of the current detection has found.

According to another advantageous embodiment, the electronic device is a consumption meter for detecting an electrical or thermal consumption or a flow meter for detecting a flow rate. Such consumption meters are, for example, energy meters, in particular heat meters, cooling meters or combined heat/cooling meters. All of these meters contain in their current structural form electronic components and therefore require for correct operation an electrical energy supply. To this end, they are provided with an energy storage unit, for example, in the form of a battery or an accumulator. In order to reduce the maintenance complexity, the energy storage unit of these meters should be replaced or recharged in a targeted manner, that is to say, only shortly before it no longer contains sufficient charge to supply the respective meter.

Another object of the invention involves providing a method for operating an electronic device of the type described in the introduction with improved properties compared with the prior art.

In order to achieve this additional objective, a method according to the features of claim 9 is set out. In the method according to the invention for operating an electronic device, the electrical energy required for operating the electronic unit is at least partially stored temporarily in a buffer capacitor which is connected to the energy connection parallel with the electronic unit and fed at the energy connection into the electronic unit. Furthermore, the electrical supply current, in particular between an output connection of the energy storage unit and the buffer capacitor, is detected and from the detected electrical supply current an electrical charge quantity which has been taken from the energy storage unit and a residual electrical charge quantity still currently stored in the energy storage unit are established.

The current residual charge quantity Qi<(t) is determined in particular by means of an evaluation, preferably a digital evaluation, of the equation (1) which has already been discussed above in connection with the electronic device according to the invention:

QRW = QO'QECO ⁼ Qo" f _tg lv(t)dt (1)

In particular, it is further possible to determine from the established residual electrical charge quantity Qi<(t) still currently stored in the energy storage unit a remaining availability time of the energy storage unit, preferably to display it and/or preferably to transmit it to another unit or device for further processing of this information. The remaining availability time is in this instance preferably determined by means of a calculation in the context of which, for example, the established residual electrical charge quantity Qi<(t) still currently stored in the energy storage unit is divided by a typical value of the supply current, for example, a supply current mean value or a supply current empirical value.

The method for operating an electronic device is in particular used in a consumption meter for detecting an electrical or thermal consumption or in a flow meter for detecting a flow rate. The method according to the invention and the embodiments thereof afford substantially the same advantages which have already been described in connection with the electronic device according to the invention and the embodiments thereof.

An embodiment is advantageous in which the electrical supply current is detected by means of an electrical current measurement resistor. In particular, to this end a voltage measurement is also carried out on the current measurement resistor. Preferably, the current measurement resistor is connected between a first electrical connection location of an output connection of the energy storage unit and the buffer capacitor.

According to another advantageous embodiment, the residual electrical charge quantity which is still stored in the energy storage unit is established in a cyclical manner at different establishment times which are temporally spaced apart from each other by an averaging interval.

According to another advantageous embodiment, the electrical supply current is detected in a cyclical manner at different detection times which are temporally spaced apart from each other by an averaging interval. Furthermore, in particular from the values of the electrical supply current which are detected within each of the averaging intervals, a supply current mean value for the relevant averaging interval and from this the electrical charge quantity taken in this averaging interval are determined.

According to another advantageous embodiment, the supply current mean value for the relevant averaging interval is in each case determined by means of a linear averaging, a mean square root averaging or a low-pass averaging.

According to another advantageous embodiment, there is provided for the measurement interval a value which is smaller than half of the product of the values of the buffer capacitor and a current measurement resistor.

According to another advantageous embodiment, an electrical storage supply voltage of the energy storage unit is detected. In particular, this is carried out by means of a voltage measurement unit which is connected to an output connection of the energy storage unit.

Other features, advantages and details of the invention will be appreciated from the following description of embodiments with reference to the drawings, in which:

Figure 1 is a block diagram of an electronic device having a charge-monitored energy storage unit, and

Figure 2 is an electrical circuit diagram of an embodiment of an electronic device according to Figure 1.

Components which correspond to each other are given the same reference numerals in Figures 1 and 2. Details of the embodiments explained in greater detail may also constitute an invention per se or be part of the subject-matter of an invention.

Figure 1 shows an embodiment of an electronic device 1 having a consumer in the form of an electronic unit 2, an energy storage unit 3, a buffer capacitor 4 and a measurement location 5 for detecting the electrical energy provided by the energy storage unit 3 in order to supply the electronic unit 2.

In the embodiment shown, the electronic unit 2 is a thermal consumption meter, such as, for example, a heat meter or a cooling meter. In principle, however, another embodiment of the electronic unit 2 is also possible. For operation, the electronic unit 2 requires electrical energy which is provided by the energy storage unit 3.

The energy storage unit 3 is in the embodiment shown a battery, wherein other embodiments, for example, in the form of an accumulator, are also possible.

The buffer capacitor 4 serves to temporarily store at least a portion of the electrical energy provided by the energy storage unit 3 for operating the electronic unit 2.

The measurement location 5 contains at least one current measurement location 6 for detecting an electrical supply current Iv of the energy storage unit 3. Optionally, it may also additionally have a voltage measurement location 7 for detecting an electrical storage supply voltage UB of the energy storage unit 3.

The electronic unit 2 has a digital sub-unit having, for example, a microprocessor and the conventional additional clcctrical/clcctronic components. This digital sub-unit serves in the embodiment shown to perform control/evaluation functions both in connection with the actual function of the electronic unit 2, that is, in connection with the thermal consumption metering, and in connection with the monitoring of the charge state of the energy storage unit 3. A logical or physical portion of the digital sub-unit can thus be understood to be a control/evaluation unit 8 for monitoring the charge state of the energy storage unit 3. The control/evaluation unit 8 is consequently in the embodiment shown an integral component of the electronic unit 2. However, there are also alternative embodiments in which the control/evaluation unit 8 for monitoring the charge state of the energy storage unit 3 is a separate unit or sub-assembly which is independent from the electronic unit 2.

The control/evaluation unit 8 is configured, from the measurement values detected at the measurement location 5, that is to say, from the measurement values of the supply current Iv and where applicable the storage supply voltage UB, to establish an electrical charge quantity Qi ( t) which has been taken from the energy storage unit 3, a residual electrical charge quantity Qi<(t) still currently stored in the energy storage unit 3 and a remaining availability time period of the energy storage unit 3. The remaining availability time period is in this instance the time remaining until the time at which the energy storage unit 3 will no longer supply sufficient electrical energy for supplying the electronic unit 2 and therefore has to be replaced. The replacement is thus carried out particularly only when it is actually required. The information established from measurement values in a manner substantiated in the electronic device 1 in relation to the remaining availability time of the energy storage unit 3 consequently advantageously enables a very efficient and selective maintenance of the energy storage unit 3.

The related operating method of the control/evaluation unit 8 or the method implemented in the control/evaluation unit 8 is explained in greater detail below.

The control/evaluation unit 8 is configured to determine the residual charge quantity Qi<(t) currently still remaining in the energy storage unit by means of a digital evaluation of the equation (1) which has already been set out above:

QRW = QO'QECO ⁼ Qo" f _tg lv(t)dt (1) where Qo is the initial charge quantity of the energy storage unit 3, Qift) is the charge quantity previously taken from the energy storage unit 3, t is the current time, to is the start time from which the energy output from the energy storage unit 3 is carried out, and Iv(t) is the electrical supply current at the respective time t.

The establishment of the residual charge quantity Qi<(t) is carried out in a cyclical manner at different establishment times t with the index i = { 1; n}, which as n is a natural number. Between two temporally successive establishment times t and t+i, there is in each case a uniform time period in the form of an averaging interval turn. Within an averaging interval turn, the supply current Iv(t) is also detected in a cyclical manner at different detection times t, k, wherein the first index i indicates the number of the relevant averaging interval and the second index k with k = { 1; m}, which as m is a natural number, indicates the number of a measurement interval located within the relevant averaging interval. The measurement interval t\i _css is in this instance the uniform time period which is located in each case between two temporally successive measurements of the supply current Iv(t).

Within the digital control/evaluation unit 8, the result of the similar equation (1) which has an integral relationship at the time t at the end of the averaging interval with the number i is approximately determined by means of the following iterative discrete relationship: with

QR U) = Qo-QE(tl) ⁼ Qo'Iv_Mit( ^t l)* ^t Mitt ( ³ ) indicates the residual charge quantity at the end of the averaging interval with the number i, Qi<(t ,-i ) indicates the residual charge quantity at the end of the previous averaging interval with the number i-1, Q _o indicates the initial charge quantity, Qi (t ) indicates the charge quantity taken within the averaging interval with the number i, tuitt indicates the duration of an averaging interval and Iv_Mitt(ti) indicates a supply current mean value of the supply current Iv(t) which is determined with the number i in the averaging interval. The supply current mean value Iv_Mitt(ti) may in this instance be a linear or square mean value of all measurement values of the supply current Iv(t) detected within the relevant averaging interval with the number i. A formation by means of an iterative discrete low-pass averaging in accordance with: is also possible, where q is a real number greater than zero and less than one. The supply current mean value Iv_Mitt(ti) to be used in the equations (2) and (3) is equal to the value of Iv_Mitt(ti,k=m), which is produced from the equation (4) for the time ti.k= _m , that is to say, at the end of the relevant averaging interval.

The anticipated remaining period of time ILE to the end of charge, that is to say, up to the time from which there will no longer be sufficient electrical energy in the energy storage unit 3 to supply the electronic unit 2 (= remaining availability time period) is derived from the equation: where Qi<(t) again indicates the current residual charge quantity in the energy storage unit 3, Iv Mitt indicates the mean value of the supply current I _v (t) determined in the last or current averaging interval and tsp indicates an in particular optional time safety buffer. This safety buffer preferably prevents the energy storage unit 3 from being used until the very last possible moment and then potentially still failing prior to a replacement or a recharging. Figure 2 shows an electrical circuit diagram of an embodiment of the electronic device 1 according to Figure 1.

The (real) energy storage unit 3 is illustrated by a series connection of an ideal battery 9 having an internal resistor 10 having the resistance value R The energy storage unit 3 has an output connection 11 whose first electrical connection location 12 is connected to a current measurement resistor 13 having a resistor value Ry of 100 Q. The inner resistor 10 and the current measurement resistor 13 form a voltage divider through which the electrical supply current Iv flows. The current measurement resistor 13 and a high- resistance measurement pick-up of the voltage Ui which drops over it are in the same manner as an (optional) amplifier 14 and a voltage measurement unit 15 components of the current measurement location 6. In the embodiment shown, the voltage measurement unit 15 is further an integral component of the controFevaluation unit 8. In an alternative embodiment which is not shown, however, the voltage measurement unit 15 may also be constructed separately from the control/evaluation unit 8. The amplifier 14 can in particular be switched on/off in order to minimise the energy requirement for the amplification of the measurement signal (= voltage Ui). The amplifier 14 is preferably only switched on at the significant times at which a detection of the supply current Iv is carried out, that is to say, in particular in a cyclical manner with the spacing of the measurement interval t\u _ss . The amplifier 14 adapts the level of the voltage Ui tapped at the current measurement resistor 13 to the input level of the following voltage measurement unit 15. The amplified voltage Uf is then applied at the input thereof.

The series connection of the energy storage unit 3 and the current measurement resistor 13 is arranged parallel with the buffer capacitor 4 with a capacitance value C of 5 F. Furthermore, the buffer capacitor 4 is also located parallel with an energy connection 16 of the electronic unit 2. It bridges the energy connection 16. The supply current Iv charges the buffer capacitor 4 so that electrical energy of the energy storage unit 3 is partially temporarily stored at that location. The supply of the electronic unit 2 with electrical energy in the event of a load is then carried out both from the intermediate store of the buffer capacitor 4 and from the energy storage unit 3. The time constant of the RC member from the current measurement resistor 13 and the buffer capacitor 4 determines the charging/discharging operations of the buffer capacitor 4. The measurement interval t\u _ss which is mentioned above and which indicates the spacing between two times for detecting the supply current Iv is in particular less than 50% of the time constant of this RC member. In the embodiment shown, the measurement interval is t\u _ss 240 s.

As a component of the (optional) voltage measurement location 7, a voltage divider 18 which can be switched on/off by means of a switch 17 is arranged parallel with the output connection 11 of the energy storage unit 3. The ability to switch the voltage divider 18 on/off serves, in a similar manner to the amplifier 14, which can be switched on/off, of the current measurement location 6, to minimise the energy requirement for the detection of the storage supply voltage UB of the energy storage unit 3.

The voltage divider 18 bridges the output connection 11 in the switched-on state. It is a series connection of a first voltage divider resistor 19 having a resistance value RMUI and a second voltage divider resistor 20 having a resistor value RMU2. The voltage divider 18 may have any dividing ratio. Even the extreme case of an infinitesimal first voltage divider resistor 19, that is to say, a resistance value RMUI of zero, and an infinite second voltage divider resistor 20 is possible. In particular, the dividing ratio can be selected depending on the input level of the following voltage measurement unit 15.

The voltage UB’ dropping at the second voltage divider resistor 20 is used as a measurement for the storage supply voltage UB and is supplied for detection by means of an again high-resistance measurement tap of the voltage measurement unit 15. The voltage measurement location 7 consequently has as components at least the voltage divider 18, the switch 17, the high-resistance measurement tap for the voltage UB’ dropping at the second voltage divider resistor 20 and the voltage measurement unit 15. The latter may be a component both of the current measurement location 6 and of the voltage measurement location 7. The association is carried out, for example, by means of a switch 21. In the control/evaluation unit 8, the detected storage supply voltage UB is used for additional monitoring of the state of the energy storage unit 3. In particular, with this additional measurement information, the remaining availability time period ILE obtained from the detection of the supply current Iv is verified and/or examined for plausibility.

On the whole, the electronic device 1 enables a substantiated statement which is in particular supported by detected measurement variables relating to the state of the energy storage unit 3, in particular relating to the residual electrical charge quantity QR still currently stored in the energy storage unit 3 and in a manner derived from this relating to the remaining availability time period ILE. Consequently, the energy storage unit 3 can be used as long as possible without there being the threat of a risk of failure of the electronic device 1 as a result of electrical energy no longer being available. The maintenance with a replacement of the energy storage unit 3 can be carried out only when the energy storage unit 3 is actually discharged to such an extent that an operational readiness of the electronic device 1 is no longer ensured.