Testing device for testing the pressure resistance of sensors

Abstract

Testing device for testing the pressure resistance of sensors with a pump arrangement for generating pulsating pressure peaks in a pressure chamber (6), with a control and evaluation unit (20) in which the signals from several sensors (7, 8a, 8b, 8c) connected to the pressure chamber are evaluated, wherein a sensor (7) serves for pressure monitoring in the pressure chamber (6), characterized in that the pump arrangement has a plunger or piston pump (4) and the pressure chamber (6) has a volume adjustable via an actuator (10), which can be adjusted by means of the control and evaluation unit (20) so that a predetermined pressure peak is reached.

Description

The invention relates to a testing device and a method for testing the pressure resistance of sensors according to the preamble of claim 1 or a method according to claim 9. Testing devices for the pressure resistance of sensors are already known. They are used, among other things, for endurance testing and accelerated life cycle testing of sensors, particularly with regard to quality control and quality assurance. Depending on their nominal pressure range, the sensors are typically tested with pulsating pressure peaks in both the nominal and overload ranges. Conventional standard hydraulic test systems and their components, which are necessary for generating pulsating pressure peaks, are implemented using special fast-switching proportional valves. However, these test systems are only suitable up to a pressure rating of approximately 600 bar. Alternatively, testing devices are available that generate pressures exceeding 600 bar using cascading (mechanical pressure intensifiers across piston diameters). To generate such pressure pulses, the low pressure in the primary circuit is pulsed in these systems. These testing devices are, however, very inefficient in terms of energy consumption. Furthermore, the testing frequency (cycle rate) is low. The usable test media are also very limited, as lubrication of the system is necessary and unavoidable mixing of the media occurs due to a sealing gap between the primary and secondary circuits. Furthermore, setting the desired test pressure is very complex with conventional testing equipment. DE 819 729 B discloses a device for measuring pulsating forces, in which a pressure gauge is connected via a check valve and has an adjustable leakage device so that the reading can also follow decreasing pressures. Furthermore, DE 37 07 565 A1 discloses a method for generating hydrodynamic pressure pulses by means of a piston that acts on a closed volume of liquid in a measuring chamber by means of a falling weight. DE 10 2006 005 065 A1 also discloses a sensor test stand with a spherical sensor mount in which radial channels are connected to each other via a common fluid chamber to achieve a uniform pressure distribution across a plurality of sensors. The object of the invention is to provide a testing device for testing the pressure resistance of sensors that does not have the aforementioned disadvantages, in particular has a significantly lower energy consumption, easily generates high pressure peaks of up to 2000 bar, allows for easy control of the pressure peaks, and is simple and cost-effective in design. This problem is solved by the test device specified in claim 1 for testing the pressure resistance of sensors or by the method specified in claim 9. Advantageous further developments of the invention are specified in the dependent claims. The essential idea of ​​the invention is to use a plunger or reciprocating piston pump as the pumping arrangement. This pump forces the pressure medium into a pressure chamber whose volume is adjustable. The maximum pressure peak value depends directly on the volume of the pressure chamber. The volume of the pressure chamber can be varied via a control and evaluation unit. A pressure sensor measures the current system pressure, and if there are deviations from the setpoint values, the pressure is adjusted by a control unit according to the control corridors or limits. The pressure chamber can be set to continuous operation during the start-up of the test facility until complete venting has taken place. A test device according to the invention has a significantly lower power consumption, since only a relatively small volume is present that needs to be cyclically compressed. The invention is explained in more detail below with reference to an embodiment shown in the drawing. The only figure shown depicts a testing device according to the invention in a very schematic representation. Pulsating pressure peaks are generated in a pressure chamber 6 using a plunger or reciprocating pump. For this purpose, the pressure chamber 6 is connected to a corresponding pump 4. The volume of the pressure chamber 6 is approximately 4 cl. A pressure sensor 7 and further sensors 8a, 8b, 8c, which are to be tested, are arranged on the pressure chamber. The pressure sensor 7 serves to detect and control the pressure in the pressure chamber 6. All sensors 7, 8a, 8b, 8c are connected to an evaluation and control unit 20. The medium supplied to pump 4 is under a pre-pressure generated by a feed pump 1. The volume of the pressure chamber 6 can be varied via a piston 9a, which is actuated by a spindle drive 11 via an adjusting element consisting of an adjusting spindle 10. The spindle drive 11 is connected to the control and evaluation unit 20 (e.g., PLC). This test setup allows for lifetime testing of pressure sensors using dynamic pressure cycles as a quality criterion for the accuracy and strength specifications. It generates test or load profiles for the defined loading of test specimens with sinusoidal pressure curves. The test pressure is generated using a plunger pump. The system is designed for operation with tap water or demineralized water. The test sequence or profiles, consisting of pressure head, test frequency, pause times, and number of load cycles, are entered into a test mask in the evaluation and control unit 20, e.g., a PLC. The test profiles are stored within the PLC. The target pressure is entered via the PLC and regulated by corresponding output modules using a mechanical actuator to change the test chamber volume. Using multiple adapters, up to 21 test subjects can be tested simultaneously. The function of the testing device according to the invention is explained in more detail below. The sensors 8a, 8b, 8c to be tested are screwed onto the pressure chamber 6 before the start of a test. Before the actual test begins, piston 9 is raised to a position that allows for automatic venting. At the start of a test, the maximum pressure value must be set or entered via a central control system, such as a PLC. For this purpose, with pump 4 running, piston 9 is slowly moved downwards to reduce the volume. The pressure in the pressure chamber is monitored by the control and evaluation unit 20 using pressure sensor 7. Once the desired maximum pressure value is reached, piston 9a remains in its current position. The maximum pressure value is reached precisely when the piston of pump 4 reaches the upper reversal point of its stroke. The medium then expands again. At the lower reversal point of the piston's stroke, the pressure chamber is virtually depressurized.When pressure sensors with a 4-20 mA signal output are tested, the measurement signal varies continuously between 4 and 20 mA. The maximum pressure value set on the pressure sensor itself, which corresponds to a measurement signal of 20 mA, is significantly lower than the maximum pressure value at the pressure peak. If a pressure sensor fails during a test, the measurement signal supplied by that sensor no longer varies between 4 and 20 mA. Such a failure can be registered by the control and evaluation unit 20. During the intake stroke, an inlet valve 3 located in the pump 4's inlet is opened. The inlet is connected to a pre-pump that supplies the pressure medium at low pressure. The pre-pump only needs to deliver as much medium as is lost through leakage during a working stroke. As soon as the piston reaches its bottom position, the inlet valve closes and the medium is compressed. As the piston continues its movement, the medium is compressed, resulting in a corresponding pressure increase. The maximum pressure is reached at the piston's top position. To prevent damage to pump 4, the maximum possible compressibility of the pressure medium must not yet be reached at the top position. The test is terminated after the specified number of pressure peaks has been reached. The test pressure is then reduced to prevent any pressure surges during shutdown. Pump 4 is switched off, and sensors 8a, 8b, and 8c can be easily unscrewed from the pressure chamber. The test specimens (sensors 8a, 8b, and 8c) are sealed using a special metal-to-metal seal (metallic sealing chamfer). The device according to the invention is characterized by its very low energy consumption, even when achieving high test pressures up to 2000 bar. The power consumption of the test device according to the invention is less than 10 percent of that of a conventional test device, since only the leakage volume needs to be compensated for with each stroke. This leakage volume is used to continuously draw heat energy from the system. The spindle drive allows the desired maximum pressure value of a pressure peak to be reached quickly, very accurately and easily. Overshooting pressures during switching on and off processes, which would distort the load situation on the test specimens, can be ruled out due to the control and regulation system. Using multiple adapters, up to 21 test subjects can be tested simultaneously. The invention describes a test device for sensors that generates a pulsating (sinusoidal test pressure profile) without proportional valves at pressure levels > 600 bar up to 2000 bar. Further advantages include: fewer components (pressure-loaded parts / valves), fewer expected failure mechanisms, and lower energy consumption. The test medium used in this design is relatively freely selectable, due to a separate lubrication circuit or the separation of the test medium from the lubrication within the plunger pump. The test frequency can be variably selected by means of the plunger pump's stroke frequency. To simulate a typical lifetime test or life cycle, the test or cycle frequency is selected as high as possible (>10 Hz). This ensures that corresponding test results are obtained even with measurement requirements of up to 100 million load cycles within a reasonable timeframe.Some of the collected data is also included in the datasheet for such sensors. Such testing equipment is also known as pressure pulse test benches. Compared to conventional testing equipment for testing the pressure resistance of sensors, which typically have a power consumption of 120 kW, the testing equipment according to the invention has a power requirement of only 20 kW. When the test device according to the invention is started up, the system is automatically vented. Otherwise, the compressibility of the trapped air would prevent the desired test pressure from being reached. This also avoids other undesirable effects such as cavitation, micro-diesel effects, etc. The test device according to the invention is also suitable for continuous operation. Any number of test cycles with 100 million or more pressure peaks can be performed. The method according to the invention makes it possible to easily test the pressure resistance of sensors. The test device allows for the easy generation of pulsating pressure peaks. It is therefore suitable not only for testing sensors but also as a device for testing other components / devices such as pressure lines, pressure hoses, rails, etc. Therefore, a claim was also made for a corresponding device.

Claims

Testing device for testing the pressure resistance of sensors with a pump arrangement for generating pulsating pressure peaks in a pressure chamber (6), with a control and evaluation unit (20) in which the signals from several sensors (7, 8a, 8b, 8c) connected to the pressure chamber are evaluated, wherein a sensor (7) serves for pressure monitoring in the pressure chamber (6), characterized in that the pump arrangement has a plunger or piston pump (4) and the pressure chamber (6) has a volume adjustable via an actuator (10), which can be adjusted by means of the control and evaluation unit (20) so that a predetermined pressure peak is reached. Test device according to claim 1, characterized in that the variable volume of the pressure chamber (6) is adjustable via a slide (9) with a spindle drive (11). Testing device according to one of the preceding claims, characterized in that the testing device is designed such that pressure peaks up to 2000 bar can be achieved with a frequency of at least 10 Hz. Testing device according to one of the preceding claims, characterized in that the testing device is designed for test cycles with 100 million pressure peaks. Test device according to one of the preceding claims, characterized in that the further connected sensors (8a, 8b, 8c) are pressure, temperature or flow sensors. Test device according to one of the preceding claims, characterized in that the further sensors (8a, 8b, 8c) have 4-20 mA signal outputs. Test apparatus according to one of the preceding claims, characterized in that the volume of the pressure chamber (6) is approximately 4 cl. Device for generating pulsating pressure peaks in a pressure chamber (6), with a pump arrangement, characterized in that the pump arrangement comprises a plunger or reciprocating piston pump (4) and the pressure chamber (6) has a volume adjustable via an actuator (10), wherein the actuator (10) is designed as a slide (9) with a spindle drive (11), and the volume is adjustable by means of the control and evaluation unit (20) so that a predetermined pressure peak is achieved. Method for testing the pressure resistance of sensors using a test device according to any of the preceding claims 1-7.

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