Piezoelectric measuring device and method for operating same

Abstract

The invention relates to a piezoelectric measuring device having a sensor element for generating a measurement signal for a pressure to be measured and a conductor element for conducting the measurement signal to a data detection device which detects and analyses the conducted measurement signal; the sensor element includes: an operational amplifier having an inverting input terminal and an output terminal; the feedback capacitor is arranged in parallel with the inverting input end and the inverting output end of the operational amplifier; the reset switch element is arranged in parallel with the inverting input end and the inverting output end of the operational amplifier; the data detection device is configured to supply a supply voltage to the sensor element, the data detection device having a measurement period circuit configured to switch on the supply voltage of the sensor element before the start of a measurement period and to switch off after the end of the measurement period; and the sensor element has a power-on reset logic configured to detect the presence of the supply voltage and, in the presence of the supply voltage, close and open the reset switching element again before the start of the measurement period.

Description

[0001] This application is a divisional application of Chinese Patent Application No. 202311362814.5, filed on October 19, 2023, entitled "Piezoelectric Measuring Device and Method for Operating the Measuring Device". Technical Field

[0002] This invention relates to a piezoelectric measuring device for measuring pressure, particularly for use in the field of injection molding for measuring internal mold pressure. A key feature of the measuring device according to the invention is its reliable, or rather, safe, measurement of internal mold pressure. Furthermore, the invention relates to a method for operating the measuring device, which is constructed, in particular, according to the method and manner of the invention. Background Technology

[0003] A piezoelectric measuring device having the features described in the preamble of claim 1 is known from patent document CH542434A5. This piezoelectric measuring device has a sensor element. The sensor element includes a piezoelectric element, an operational amplifier, a feedback capacitor, a discharge resistor, and a reset switch. The internal pressure of the mold to be measured acts as a force on the piezoelectric element. Under the action of this force, the piezoelectric element generates a charge. This charge is converted into a voltage signal by the operational amplifier. The feedback capacitor is arranged in parallel with the inverting input and output of the operational amplifier and acts as an integrator. The discharge resistor and the reset switch are also arranged in parallel with the inverting input and output of the operational amplifier. The discharge resistor causes the feedback capacitor to discharge continuously, thereby preventing the feedback capacitor from being over-controlled (Übersteuerung) due to fault current in the sensor element after a period of time, which occurs particularly in quasi-static measurements due to the finitely high insulation resistance in the sensor element. Furthermore, by closing the reset switch, the feedback capacitor is discharged before the measurement begins, thus returning the sensor element to zero. During the measurement, the reset switch is open.

[0004] Furthermore, as is known from patent document WO2014 / 120430A1, in combination Figure 2 Among the disclosed piezoelectric measuring devices, a data detection device with a switch is provided. This switch is used for switching between different power supply voltages. Summary of the Invention

[0005] The piezoelectric measuring device according to the invention includes a sensor element configured to generate a measurement signal in response to the pressure to be measured. The piezoelectric measuring device has a cable for transmitting the measurement signal to a data detection device designed to detect and analyze the transmitted measurement signal. The sensor element has an operational amplifier having an inverting input and an output. The sensor element has a feedback capacitor arranged in parallel with the inverting input and output of the operational amplifier. The sensor element also has a reset switch element arranged in parallel with the inverting input and output of the operational amplifier. The data detection device is additionally designed to provide a power supply voltage to the sensor element.

[0006] The piezoelectric measuring device according to the present invention is based on the following idea: constructing a sensor element known from the prior art, which has an operational amplifier and a feedback capacitor, but no discharge resistor.

[0007] Although the discharge resistor used to discharge the feedback capacitor is omitted, the present invention still provides reliable discharge of the feedback capacitor with relatively low switching technology costs, thereby enabling quasi-static measurement. In this context, a piezoelectric measuring device according to the present invention is proposed, wherein the data detection device of the measuring device additionally includes a measurement cycle circuit configured to turn on the power supply voltage of the sensor element before the start of the measurement cycle and turn off the power supply voltage of the sensor element after the end of the measurement cycle. Because, according to the present invention, the sensor element has a power-on reset circuit configured to detect the presence of the power supply voltage and, if the power supply voltage is present, to close and then open the reset switch element again before the start of the measurement cycle. This ensures that the feedback capacitor is at least indirectly discharged before the start of the measurement cycle.

[0008] Preferred extensions of this piezoelectric measuring device will be given below.

[0009] Specifically, the measurement cycle circuit has a power switch element that is used to turn the power supply on or off to the sensor element.

[0010] Preferably, the discharge of the feedback capacitor is achieved by means of a power-on reset circuit: that is, the power-on reset circuit is configured as an actuating reset switch element to discharge the feedback capacitor.

[0011] Preferably, the data detection device has a balancing circuit configured to balance the first measurement signal derived from the sensor element. This, in particular, improves measurement accuracy during subsequent stages of the measurement.

[0012] According to a preferred extension of the reset circuit, the reset circuit includes power-on reset logic that closes a reset switch element to discharge a feedback capacitor after a predetermined voltage value has been exceeded for a specified time, and then opens the reset switch element again.

[0013] According to the present invention, signal transmission and power supply of the sensor element can also be achieved through a conductor element, which is a single-core cable (Einleiterkabe) with a single signal conductor. Therefore, no additional conductor is required to trigger a reset on the feedback capacitor, which is particularly advantageous for space-constrained injection molds.

[0014] In an alternative circuit, sensor element 10 can be specified to have a 4.20 mA transmitter and a current interface. The 4.20 mA transmitter is connected to the output of an operational amplifier and is configured to convert the measurement signal, provided by the operational amplifier as a voltage signal, into a current signal. The 4.20 mA transmitter is connected to the current interface. The current interface is connected to a conductor element. The current signal is conducted from the 4.20 mA transmitter through the current interface and the conductor element to a data detection device. The data detection device also has a shunt element and another operational amplifier connected downstream of the power supply. The shunt element and the other operational amplifier are configured to convert the conducted current signal back into a voltage signal. The measurement signal is thus conducted from the sensor element to the data detection device in a current-adapted manner. This is particularly advantageous in harsh environments with high-intensity interference, such as during injection molding operations, because such current-adapted conduction offers high reliability.

[0015] The sensor element may have a TEDS (Digital Data Storage System) that stores digital data about the sensor element and / or measurement points. Accordingly, the data detection device has read / write circuitry configured to read digital data from and / or write digital data to the TEDS. This allows digital data from the sensor element to be automatically provided to the data detection device without requiring manual input via a dedicated input device. This digital data about the sensor element includes sensor type, sensitivity, calibration data, etc. Automated data provision also avoids input errors, improving the quality and usability of the piezoelectric measuring device.

[0016] The sensor element has a piezoelectric element that generates an electric charge under the pressure to be measured, and this charge flows into the inverting input of the operational amplifier. Furthermore, considering the particularly compact structure of the measuring device, it is advantageous that the operational amplifier and feedback capacitor are arranged together with the piezoelectric element in the same housing as the sensor element.

[0017] Piezoelectric measuring devices are preferably used to measure the internal pressure of injection molds during operation, and are designed accordingly. This specifically includes designing piezoelectric measuring devices or sensor elements that can withstand long-term operating temperatures typically exceeding 100°C and relatively high pressures without damage.

[0018] The present invention also relates to a method for operating a piezoelectric measuring device, particularly constructed in the manner and method described above. Here, a measurement signal is generated by means of a sensor element for the pressure to be measured, and this measurement signal is transmitted to a data detection device via a conductor element, which detects and analyzes the transmitted measurement signal. The sensor element has an operational amplifier having an inverting input and an output. The sensor element has a feedback capacitor arranged in parallel with the inverting input and output of the operational amplifier. The sensor element also has a reset switch element arranged in parallel with the inverting input and output of the operational amplifier. Additionally, the data detection device provides a power supply voltage to the sensor element. The method according to the invention is characterized in that the data detection device has a measurement cycle circuit that, in a first step, turns on the power supply voltage to the sensor element before the start of the measurement cycle; the sensor element has a power-on reset logic that, in a second step, detects the presence of the power supply voltage and, if the power supply voltage is present, closes the reset switch element and then opens it again before the start of the measurement cycle; and in a fifth step, the measurement cycle circuit disconnects the power supply voltage to the sensor element after the end of the measurement cycle.

[0019] According to a preferred extension of the method of the present invention, the method is used to measure the internal pressure of an injection mold during operation. The measurement cycle for measuring the internal pressure of the mold begins as follows: In a first step, a power supply voltage for a sensor element is provided through a measurement cycle circuit. In a second step, the presence of the power supply voltage is detected by means of reset logic in a power-on reset circuit, which then closes a reset switch element for a predetermined time period, discharging a feedback capacitor through this closed reset switch element. Subsequently, the power-on reset circuit opens the reset switch element again. In a third step, the measurement cycle for measuring the internal pressure of the mold is executed for a certain duration, wherein the charge generated by the piezoelectric element is converted into a measurement signal by means of an operational amplifier, and this measurement signal is detected and analyzed by a data detection device. After the measurement cycle ends, in a fifth step, the power supply voltage to the sensor element is disconnected by the measurement cycle circuit.

[0020] Preferably, the data detection device has a balancing circuit that balances the first measurement signal detected by the data detection device in the fourth step to improve measurement accuracy.

[0021] More preferably, the sensor element has a TEDS, a first diode, and a second diode, wherein the TEDS stores digital data about the sensor element and / or the measurement point. Accordingly, the data detection device has a read / write circuit and a read / write switch element. To initiate a read / write operation, in a zero-step, the read / write circuit activates the read / write switch element. The read / write circuit provides a negative DC voltage applied to the conductor element, causing the first diode to de-conduct and the second diode to conduct. The read / write circuit is configured to read digital data from the TEDS and / or write digital data to the TEDS. To terminate the read / write operation, the read / write switch element is deactivated by the read / write circuit.

[0022] Further advantages, features and details of the present invention will become apparent below through the description of preferred embodiments of the invention and the accompanying drawings. Attached Figure Description

[0023] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings, which provide further advantages, features and details of the invention.

[0024] Figure 1 A first embodiment of a piezoelectric measuring device 100 for measuring the internal pressure in an injection mold is shown.

[0025] Figure 2 A second embodiment of a piezoelectric measuring device 100 for measuring the internal pressure in an injection mold is shown.

[0026] Figure 3A third embodiment of a piezoelectric measuring device 100 for measuring the internal pressure in an injection mold is shown.

[0027] Figure 4 A fourth embodiment of a piezoelectric measuring device 100 for measuring the internal pressure in an injection mold is shown.

[0028] Figure 5 The operation is shown according to Figures 1 to 4 A flowchart of steps S0 to S5 of the method V of one of the piezoelectric measuring devices 100.

[0029] The same elements or elements with the same function have the same reference numerals in the drawings.

[0030] List of reference numerals

[0031] 10: Sensor Components

[0032] 12: Data detection device

[0033] 13: Conductor element

[0034] 14: Shell

[0035] 15: Electrical grounding

[0036] 18: Piezoelectric elements

[0037] 20: Operational amplifier

[0038] 21: TEDS

[0039] 22: Feedback capacitor

[0040] 23: Current Interface

[0041] 24: 4..20 mA transmitter

[0042] 25: Power-on reset circuit

[0043] 26: Reset Logic

[0044] 27: Reset switch element

[0045] 28: First Diode

[0046] 29: Second Diode

[0047] 30: Voltage power supply

[0048] 32: Power switching components

[0049] 35: Measurement Period Circuit

[0050] 36: Constant current regulating diode

[0051] 40: Balancing Circuit

[0052] 41: Shunt element

[0053] 42: Another operational amplifier

[0054] 50: Read / Write Circuit

[0055] 52: Read / write switch element

[0056] 60: Voltage signal

[0057] 100: Piezoelectric measuring device

[0058] D: Digital Data

[0059] M: Measurement signal

[0060] U: Power supply voltage

[0061] U Negative DC voltage

[0062] V: Method

[0063] S0: Previous steps

[0064] S1: First Step

[0065] S2: Second step

[0066] S3: Third Step

[0067] S4: Fourth Step

[0068] S5: Fifth Step Detailed Implementation

[0069] Figure 1 A first embodiment of the piezoelectric measuring device 100 is shown, which is preferably used to measure the internal pressure of an injection mold (not shown) during operation. The injection mold can be used for injection molding of liquefiable materials such as plastics and metals.

[0070] It should be noted that the piezoelectric measuring device 100 can also be used in other applications in principle. For example, if the cycle time for analyzing signals during the assembly process is short enough, it can be used for force monitoring during the assembly process.

[0071] The piezoelectric measuring device 100 has a sensor element 10 arranged in a housing 14. The sensor element 10 has the following function: generating a measurement signal M for the internal pressure of the mold to be measured.

[0072] The piezoelectric measuring device 100 has a data detection device 12, which is arranged separately from the sensor element 10. The data detection device 12 has the function of detecting and analyzing the measurement signal M from the sensor element 10 in order to determine the internal pressure of the mold based on the analysis.

[0073] Sensor element 10 is electrically connected to data detection device 12. This electrical connection is achieved through conductor element 13. Preferably, conductor element 13 is a single-core cable with a single signal conductor. Conductor element 13 is used to transmit the measurement signal M from sensor element 10 to data detection device 12, and to provide a power supply voltage U to sensor element 10 through data detection device 12. The housing 14 of sensor element 10 and data detection device 12 share the same electrical ground 15. Preferably, the housing 14 of sensor element 10 and data detection device 12 are located on the same electrical ground 15 with respect to the injection mold. Electrical ground 15 forms a reference potential for transmitting the measurement signal M and providing the power supply voltage U. However, conductor element 13 may also be a two-conductor cable with a signal conductor and a ground conductor connected to electrical ground 15. The signal conductor and ground conductor are made of a conductive material such as copper.

[0074] Sensor element 10 has a piezoelectric element 18. The internal pressure of the mold to be measured acts as a force on the piezoelectric element 18, which generates an electric charge under the force. In addition to the piezoelectric element 18, sensor element 10 also has an operational amplifier 20, which has an inverting input and an output. The charge generated by the piezoelectric element 18 is, for example... Figures 1 to 4 The inverting input of operational amplifier 20 is marked with a minus sign. The non-inverting input of operational amplifier 20 is... Figures 1 to 4 The symbols are marked with a plus sign. Additionally, a feedback capacitor 22 is provided as an integrator, which is arranged in parallel with the inverting input and output of operational amplifier 20. Operational amplifier 20 and feedback capacitor 22 form a charge amplifier that converts charge into a measurement signal M. The measurement signal M can be measured at the output of operational amplifier 20. The measurement signal M is a voltage signal, typically a few volts, such as 0V to +10V, and has a dynamic range of a few kHz.

[0075] Additionally, sensor element 10 has a power-on reset circuit 25, which includes reset logic 26. The power-on reset circuit 25 acts on a reset switch element 27 arranged in parallel with the feedback capacitor 22, which, in the closed position, discharges the feedback capacitor 22.

[0076] According to Figure 1In a first embodiment of the piezoelectric measuring device 100, the measuring signal M is conducted as a voltage signal from the sensor element 10 to the data detection device 12 in a voltage-adaptive manner. The data detection device 12 is also designed to provide a power supply voltage U to the sensor element 10 via a conductor element 13. For this purpose, the data detection device 12 has a voltage source 30 having a positive DC voltage typically between +18V and +30V, which is coupled to the conductor element 13 via a constant current regulating diode 36, wherein the power supply voltage U can be turned on by a power switching element 32. The activation or operation (opening and closing) of the power switching element 32 is performed by means of a measurement cycle circuit 35.

[0077] Now refer to Figure 5 The flowchart describes in detail the operation of the piezoelectric measuring device 100 for detecting the internal pressure of an injection mold.

[0078] The measurement cycle for measuring the internal pressure of the mold operates as follows: First, in the first step S1, a power supply voltage U for the sensor element 10 is provided by correspondingly activating the measurement cycle circuit 35 and closing the voltage supply element 32. The measurement cycle circuit 35 and the voltage supply element 32 are effectively connected to each other, which in... Figures 1 to 4 It is shown in dashed lines.

[0079] The power supply voltage U is supplied to the sensor element 10 through the conductor element 13. In the second step S2, the presence or connection of the power supply voltage U in the sensor element 10 is detected by the reset logic 26. This causes the power-on reset circuit 25 to close the reset switch element 27 within a predetermined time period to discharge the feedback capacitor 22. For this purpose, the power-on reset circuit 25 and the reset switch element 27 are also effectively connected to each other, which in Figures 1 to 4 The information is shown in dashed lines. The reset switch element 27 is then disconnected again via the power-on reset circuit 25.

[0080] Now, in the third step S3, a real measurement cycle is performed for a certain duration, wherein the charge generated by the piezoelectric element 18 is converted into a measurement signal M by the operational amplifier 20. The measurement signal M is transmitted from the sensor element 10 through the conductor element 13 to the data detection device 12, and is detected and analyzed by the data detection device 12.

[0081] The data detection device 12 optionally includes a balancing circuit 40. The balancing circuit 40 has a signal input terminal, a command input terminal, and a signal output terminal. The balancing circuit 40 is connected to the conductor element 13 via the signal input terminal. Figures 1 to 4The command input terminal, shown in dashed lines, can activate the balancing circuit 40 via the measurement cycle circuit 35. In the optional fourth step S4, the balancing circuit 40 receives the measurement signal M through its signal input terminal. The first measurement signal M detected by the data detection device 12 during the measurement cycle is therefore received and balanced by the balancing circuit 40. The balancing circuit 40 outputs the balanced measurement signal as a voltage signal 60 through its signal output terminal. During balancing, the voltage level of the first measurement signal M is set to 0 V.

[0082] Then, the voltage signal 60 is analyzed during the operation of the injection molding machine, especially during the measurement cycle which typically lasts for a maximum of one minute.

[0083] In order to end the measurement cycle, in the fifth step S5, the power supply voltage U is disconnected again by the measurement cycle circuit 35 and the power switch element 32.

[0084] exist Figure 2 The second embodiment of the piezoelectric measuring device 100 shown is largely based on [the following]. Figure 1 The first embodiment of the piezoelectric measuring device 100 is described below; please refer to its description to avoid repetition. Figure 2 The second embodiment of the piezoelectric measuring device 100 and according to Figure 1 The differences in the first embodiment of the piezoelectric measuring device 100 will be explained.

[0085] According to Figure 2 In a second embodiment of the piezoelectric measuring device 100, the measuring signal M is transmitted from the sensor element 10 to the data detection device 12 as a current signal in a current-adaptive manner. For this purpose, the sensor element 10 has a 4.20 mA transmitter 23 and a current interface 24. The 4.20 mA transmitter 23 is connected to the output of the operational amplifier 20. The 4.20 mA transmitter 23 is configured to convert the voltage signal provided by the operational amplifier 20 into a current signal. Here, the voltage signal is converted into a current signal proportional to its magnitude. For example, a 0V voltage signal is converted into a 4mA current signal, and a 10V voltage signal is converted into, for example, a 4.20 mA current signal. The 4.20 mA transmitter 23 is connected to the current interface 24. Furthermore, the current interface 24 is connected to the conductor element 13. The current signal is transmitted to the data detection device 12 via the current interface 24 and the conductor element 13.

[0086] The data detection device 12 has a shunt element 41 and another operational amplifier 42 connected downstream of the voltage source 30. The shunt element 41 and the other operational amplifier 42 are configured to convert the conducted current signal back into a voltage signal. The current signal flows into the inverting input terminal of the other operational amplifier 42, marked with a minus sign in the figure. The non-inverting input terminal of the other operational amplifier 40 is marked with a plus sign in the figure. The voltage signal can be measured at the output terminal of the other operational amplifier 40. During inverse conversion, the current signal is also converted into a voltage signal proportional to its magnitude. For example, a 4mA current signal is converted into a 0V voltage signal, and a 4.20mA current signal is converted into a 10V voltage signal.

[0087] Figure 3 and Figure 4 The other two embodiments of the piezoelectric measuring device 100 shown in the figure also basically correspond to those based on... Figure 1 and Figure 2 The first two embodiments of the piezoelectric measuring device 100 are described below; therefore, please refer to their descriptions. Figure 3 and Figure 4 Two other embodiments of the piezoelectric measuring device 100 and according to Figure 1 and Figure 2 The difference between the first two implementations of the piezoelectric measuring device 100.

[0088] Sensor element 10 additionally includes a Transducer Electronic Data Sheet (TEDS) with reference mark 21. TEDS 21 is a data storage element that stores digital data D about sensor element 10 and / or measurement points. The digital data D about sensor element 10 includes sensor type, sensitivity, calibration data, etc. TEDS 21 has input and output terminals. TEDS 21 is electrically connected to conductor element 13 via the input terminal and electrically connected to ground 15 via the output terminal.

[0089] The data detection device 12 additionally includes a read / write circuit 50 and a read / write switch element 52. The read / write circuit 50 is configured to read digital data D from TEDS 21 and / or write digital data D to TEDS 21 during read / write operations. For this purpose, the read / write switch element 52 can be used to... Figure 3 and Figure 4 The instruction input terminal of the read / write circuit 50, shown in dashed lines, is activated and deactivated. According to... Figure 3 and Figure 4In the active state, the read / write circuit 50 is electrically connected to the conductor element 13. In the inactive state, the voltage source 30 is electrically connected to the conductor element 13. A first diode 28 is positioned between the end of the conductor element 13 and the operational amplifier 20. A second diode 29 is positioned between the input terminal of TEDS 21 and the conductor element 13.

[0090] During the measurement cycle, the power supply voltage U provided by voltage source 30 is applied as a positive DC voltage to conductor element 13, and the first diode 28 is turned on while the second diode 29 is not turned on. Therefore, the second diode 29 does not allow current to flow from conductor element 13 to TEDS 21. Thus, during the measurement cycle, TEDS 21 is electrically isolated from operational amplifier 20 and data detection device 12 and does not affect the measurement cycle.

[0091] Read and write operations are optional. Based on... Figure 5 In the flowchart, the read / write operation is performed in step zero, S0. In terms of timing, step zero, S0, can be performed before the other steps S1 to S5 of method V. To initiate the read / write operation, the read / write switching element 52 is activated by the read / write circuit 50. Now, the negative DC voltage U provided by the read / write circuit 50... An application is made to the conductor element 13, causing the first diode 28 to be de-conducting while the second diode 29 is conducting. Therefore, the first diode 28 prevents current from flowing from the conductor element 13 to the operational amplifier 20. Thus, during read / write operations, the operational amplifier 20 is electrically isolated from the data detection device 12 and can operate without affecting the read / write process. The read / write circuit 50 can now read digital data D from TEDS 21 and / or write digital data D to TEDS 21. To terminate the read / write operation, the read / write switch element 52 is deactivated by the read / write circuit 50.

[0092] The above four embodiments of the piezoelectric measuring device 100 can be converted or modified in various ways without departing from the concept of the present invention.

Claims

1. A piezoelectric measuring device (100), comprising: Sensor element (10), the sensor element (10) is configured to generate a measurement signal (M) in response to the pressure to be measured; Conductor element (13) for transmitting the measurement signal (M) to data detection device (12), the data detection device (12) being configured to detect and analyze the transmitted measurement signal (M); The sensor element (10) therein has an operational amplifier (20), which has an inverting input terminal and an output terminal; The sensor element (10) has a feedback capacitor (22), which is arranged in parallel with the inverting input and output of the operational amplifier (20); The sensor element (10) has a reset switch element (27) arranged in parallel with the inverting input and output of the operational amplifier (20). The data detection device (12) is additionally configured to provide a power supply voltage (U) to the sensor element (10). Its features are, The data detection device (12) has a measurement cycle circuit (35) configured to turn on the power supply voltage (U) of the sensor element (10) before the start of the measurement cycle and turn off after the end of the measurement cycle; and The sensor element (10) has power-on reset logic (25, 26), which is configured to detect the presence of the power supply voltage (U) and, if the power supply voltage (U) is present, close the reset switch element (27) and open it again before the start of the measurement cycle. The power-on reset circuit (25) is configured to actuate the reset switch element (27) to discharge the feedback capacitor (22); The reset circuit (25) includes a power-on reset logic (26), which closes the reset switch element (27) to discharge the feedback capacitor (22) after a predetermined voltage value has been exceeded for a limited time, and then disconnects the reset switch element again after the discharge.

2. The piezoelectric measuring device (100) according to claim 1, characterized in that, The measurement cycle circuit (35) is configured to turn on or off the voltage source (30) of the sensor element (10) via a power switch element (32).

3. The piezoelectric measuring device (100) according to claim 1 or 2, characterized in that, The data detection device (12) has a balancing circuit (40) configured to balance a first measurement signal (M) transmitted from the sensor element (10) to the data detection device (12).

4. The piezoelectric measuring device (100) according to any one of claims 1 to 3, characterized in that, The conductor element (13) is a single-core cable with a single signal conductor.

5. The piezoelectric measuring device (100) according to any one of claims 1 to 4, characterized in that, The sensor element (10) has a 4.20 mA transmitter (23) and a current interface (24). The 4.20 mA transmitter (23) is connected to the output of the operational amplifier (20) and is configured to convert the measurement signal (M) provided by the operational amplifier (20) as a voltage signal into a current signal. The 4.20 mA transmitter (23) is connected to the current interface (24). The current interface (24) is connected to the conductor element (13). The current signal can be conducted to the data detection device (12) through the current interface (24) and the conductor element (13).

6. The piezoelectric measuring device (100) according to claim 5, characterized in that, The data detection device (12) has a shunt element (41) and another operational amplifier (42) connected downstream of the voltage power supply (30); and the shunt element (41) and the other operational amplifier (42) are configured to convert the current signal to be conducted back into a voltage signal.

7. The piezoelectric measuring device (100) according to any one of claims 1 to 6, characterized in that, The sensor element (10) has a TEDS (21) in which digital data (D) about the sensor element (10) and / or measurement points is stored; the data detection device (12) has a read / write circuit (50) configured to read digital data (D) from the TEDS (21) and / or write digital data (D) to the TEDS (21).

8. The piezoelectric measuring device (100) according to any one of claims 1 to 7, characterized in that, The sensor element (10) has a piezoelectric element (18) that generates an electric charge under the action of the pressure to be measured, and the electric charge flows into the inverting input of the operational amplifier (20); and the operational amplifier (20) and the feedback capacitor (22) are arranged together with the piezoelectric element (18) in the same housing (14) of the sensor element (10).

9. The piezoelectric measuring device (100) according to any one of claims 1 to 8, characterized in that, The measuring device (100) is configured to measure the internal pressure of the injection mold during operation.

10. A method (V) for operating a piezoelectric measuring device (100), said piezoelectric measuring device being constructed according to any one of claims 1 to 9, in, A measurement signal (M) is generated by means of a sensor element (10) for the pressure to be measured, and the measurement signal (M) is transmitted to a data detection device (12) through a conductor element (13), which detects and analyzes the transmitted measurement signal (M). The sensor element (10) has an operational amplifier (20), which has an inverting input terminal and an output terminal. The sensor element (10) has a feedback capacitor (22), which is arranged in parallel with the inverting input and output terminals of the operational amplifier (20). The sensor element (10) has a reset switch element (27), which is arranged in parallel with the inverting input and output terminals of the operational amplifier (20). The data detection device (12) additionally provides a power supply voltage (U) to the sensor element (10). Its features are, The data detection device (12) has a measurement cycle circuit (35). In the first step (S1), the measurement cycle circuit (35) turns on the power supply voltage (U) of the sensor element (10) before the measurement cycle begins. The sensor element (10) has power-on reset logic (25, 26). In the second step (S2), the power-on reset logic (25, 26) detects the presence of the power supply voltage (U) and, if the power supply voltage (U) is present, closes the reset switch element (27) and opens it again before the start of the measurement cycle. The power-on reset circuit (25) is configured to actuate the reset switch element (27) to discharge the feedback capacitor (22); The reset circuit (25) includes power-on reset logic (26), which closes the reset switch element (27) to discharge the feedback capacitor (22) after a predetermined voltage value has been exceeded for a limited time, and then opens the reset switch element again after the discharge; and In the fifth step (S5), the measurement cycle circuit (35) disconnects the power supply voltage (U) of the sensor element (10) after the measurement cycle ends.

11. The method (V) according to claim 10, characterized in that, This method is used to measure the internal pressure of an injection mold during operation, wherein the measurement cycle for measuring the internal pressure of the mold is as follows: In the first step (S1), a power supply voltage (U) is provided to the sensor element (10) through the measurement cycle circuit (35); In the second step (S2), the presence of the power supply voltage (U) is detected by the reset logic (26) in the power-on reset circuit (25), and based on this, the power-on reset circuit (25) closes the reset switch element (27) within a predetermined time period, and the feedback capacitor (22) is discharged through the closed reset switch element (27), and then the power-on reset circuit (25) opens the reset switch element (27) again. In the third step (S3), the measurement cycle for measuring the internal pressure of the mold is performed for a certain duration, wherein the charge generated by the piezoelectric element (18) is converted into the measurement signal (M) by the operational amplifier (20), and the measurement signal (M) is detected and analyzed by the data detection device (12); and In the fifth step (S5), after the measurement cycle ends, the measurement cycle circuit disconnects the power supply voltage (U) of the sensor element (10).

12. The method (V) according to claim 11, characterized in that, The data detection device (12) has a balancing circuit (40); the balancing circuit (40) balances the first measurement signal (M) detected by the data detection device (12) in the fourth step (S4).

13. The method (V) according to any one of claims 10 to 12, characterized in that, The sensor element (10) has a TEDS (21), a first diode (28), and a second diode (29), wherein digital data (D) about the sensor element (10) and / or the measurement point is stored in the TEDS (21); the data detection device (12) has a read / write circuit (50) and a read / write switch element (52); in the zero step (S0), in order to start the read / write operation, the read / write switch element (52) is activated by the read / write circuit (50); a negative DC voltage (U) is provided by the read / write circuit (50). The negative DC voltage (U) An action is applied to the conductor element (13) such that the first diode (28) is de-conducting and the second diode (29) is turned on; the read / write circuit (50) is configured to read digital data (D) from the TEDS (21) and / or write digital data (D) to the TEDS (21); and in order to end the read / write operation, the read / write switch element (52) is deactivated by the read / write circuit (50).

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