Reliability evaluation system and evaluation method for vibration measurement cable

Abstract

A reliability evaluation system and evaluation method for a vibration measurement cable. In the system, an output end of a vibration calibration system is connected to one end of a standard capacitor and is used for loading a standard known voltage signal; the other end of the standard capacitor is connected to a charge collection system, and the standard capacitor is connected in parallel to a vibration measurement cable to be evaluated; and the charge collection system is used for collecting the total amount of charge of the standard capacitor and said vibration measurement cable. A vibration measurement cable is screened by means of measuring a noise voltage converted from the parasitic capacitance of the vibration measurement cable, wherein a cable having higher noise voltage has greater interference noise during vibration parameter collection, and has lower reliability. Thus, the evaluation method can accurately evaluate the reliability of the vibration measurement cable.

Description

A reliability testing system and method for vibration measurement cables Technical Field

[0001] This invention relates to a reliability testing method for cables, specifically to a reliability testing system and method for vibration measurement cables. Background Technology

[0002] According to the requirements of vibration measurement regulations, the reliability test indicators for cables are: cable resistance and cable insulation resistance. Current testing methods mostly involve: determining whether the cable is short-circuited, open-circuited, or damaged by rodents by measuring the cable resistance within the specified range; and then determining the cable insulation performance by measuring the insulation resistance with a megohmmeter to ensure it is not less than 500 MΩ. However, many factors affect cable noise, and relying solely on these two test indicators to judge cable performance is unreliable. Table 1 shows the insulation resistance and noise levels of a cable measured without a piezoelectric vibration sensor.

[0003] Table 1

[0004] As can be seen from Table 1, good insulation performance does not necessarily mean low noise. The disadvantage of the above method is that insulation resistance is a necessary standard for measuring cable performance, but relying solely on testing the insulation resistance of a cable cannot accurately determine its reliability. Summary of the Invention

[0005] The purpose of this invention is to solve the problem that existing cable reliability testing methods cannot accurately determine cable reliability by relying solely on testing the cable's insulation resistance, and to provide a reliability testing system and method for vibration-measuring cables.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A reliability testing system for vibration measurement cables, characterized by:

[0008] This includes a vibration calibration system, a standard capacitor, a charge acquisition system, and a piezoelectric vibration sensor;

[0009] The output of the vibration calibration system is connected to one end of a standard capacitor to load a standard known voltage signal.

[0010] The other end of the standard capacitor is connected to a charge acquisition system;

[0011] One end of the piezoelectric vibration sensor is connected to the vibration calibration system, and the other end is connected to the charge acquisition system;

[0012] The charge acquisition system is used to collect the total charge at the location;

[0013] The standard capacitor and piezoelectric vibration sensors are connected in parallel with the vibration measurement cable to be tested.

[0014] Furthermore, the standard known voltage signal is a sinusoidal signal, with a frequency of 1000Hz and a voltage of 8V during normal vibration, and a frequency of 78.125Hz and a voltage of 1.2V during low-frequency vibration.

[0015] Furthermore, the capacitance value of the standard capacitor is one of 500pF, 1000pF, 1500pF, and 2000pF.

[0016] Meanwhile, this invention also provides a reliability testing method for vibration measurement cables, using a reliability testing system for vibration measurement cables, characterized by the following steps:

[0017] S1. Measure the length of the vibration measurement cable to be tested and calculate the distributed capacitance value C of the vibration measurement cable to be tested. f Simultaneously, the vibration measurement cable to be tested is connected in parallel to a standard capacitor;

[0018] S2. Remove the piezoelectric vibration sensor, apply a standard known voltage U through the vibration calibration system, and collect the total charge q of the standard capacitor and the vibration measurement cable to be tested through the charge acquisition system. Combine the standard known voltage U and the capacitance value C of the standard capacitor to calculate the total capacitance value C1 of the vibration measurement cable to be tested.

[0019] S3. Reconnect the piezoelectric vibration sensor, remove the standard capacitor, remove the standard known voltage U, and then apply the rated voltage u to the piezoelectric vibration sensor. Collect the total charge Q of the piezoelectric vibration sensor and the vibration measurement cable to be tested through the charge acquisition system.

[0020] S4. Based on the total capacitance value C1 of the vibration measurement cable to be tested in S2 and the distributed capacitance value C of the vibration measurement cable to be tested in S1... f Calculate the parasitic capacitance C of the vibration measurement cable to be tested. j ;

[0021] S5. Calculate the charge q1 of the piezoelectric vibration sensor based on the rated voltage u and the capacitance of the piezoelectric vibration sensor; calculate the charge q1 of the piezoelectric vibration sensor based on the rated voltage u and the distributed capacitance C of the vibration measurement cable to be detected in S1. f Calculate the distributed capacitance charge q2 of the vibration measurement cable to be tested;

[0022] S6. Based on the total charge Q of the piezoelectric vibration sensor and the vibration measurement cable to be tested in S3, and the charge q1 of the piezoelectric vibration sensor and the distributed capacitance charge q2 of the vibration measurement cable to be tested in S5, calculate the charge q3 of the cable parasitic capacitance accumulation.

[0023] S7, combined with the parasitic capacitance value C of the vibration measurement cable to be detected in S4. j Calculate the cable noise voltage U based on the charge q3 accumulated by the cable parasitic capacitance in S6. 噪 ;

[0024] S8. Collect the output voltage of the piezoelectric vibration sensor and calculate the cable noise voltage U. 噪 The reliability of the vibration measurement cable under test is good when the ratio of the vibration measurement cable to the output voltage of the piezoelectric vibration sensor is not greater than 5%; otherwise, the reliability of the vibration measurement cable under test is poor.

[0025] Furthermore, the formula for calculating the total capacitance C1 of the vibration measurement cable to be tested, as described in S2, is: q=(C1+C)×U.

[0026] Furthermore, the formula for calculating the charge q3 accumulated by the parasitic capacitance of the cable as described in S6 is: Q3=Q-q1-q2.

[0027] Furthermore, the calculation of cable noise voltage U described in S7 噪 The formula is: U 噪 =q3 / C j .

[0028] The beneficial effects of this invention are:

[0029] 1. The present invention provides a reliability testing system for vibration measurement cables, which has a simple structure and good practicality.

[0030] 2. The present invention provides a reliability testing method for vibration measurement cables. By detecting the noise voltage converted from the parasitic capacitance of the vibration measurement cable, the vibration measurement cable is screened. The higher the noise voltage, the greater the interference noise during vibration parameter acquisition, and the lower the reliability. The method of the present invention can accurately detect the reliability of vibration measurement cables.

[0031] 3. The reliability testing method for vibration measurement cables of the present invention also has the advantages of simple operation and fast testing. Attached Figure Description

[0032] Figure 1 is a schematic diagram of an embodiment of the reliability testing system for vibration measurement cables according to the present invention;

[0033] Figure 2 is a schematic diagram of the detection system model used in an embodiment of the reliability detection method for a vibration measurement cable of the present invention;

[0034] Figure 3 shows the waveform of a standard known voltage signal during normal vibration in an embodiment of the reliability testing method for a vibration measurement cable of the present invention;

[0035] Figure 4 shows the waveform of a standard known voltage signal during low-frequency vibration in an embodiment of the reliability testing method for a vibration measurement cable according to the present invention. Detailed Implementation

[0036] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] This embodiment provides a reliability testing system for vibration measurement cables, as shown in Figure 1. It includes a vibration calibration system, a standard capacitor, a charge acquisition system, and a piezoelectric vibration sensor; wherein the standard capacitor has a capacitance value of 1000pF.

[0038] The output of the vibration calibration system is connected to one end of a standard capacitor to load a standard known voltage signal. The standard known voltage signal is a sine wave signal with a frequency of 1000Hz and a voltage of 8V during normal vibration, and a frequency of 78.125Hz and a voltage of 1.2V during low-frequency vibration.

[0039] The other end of the standard capacitor is connected to the charge acquisition system, and the standard capacitor is connected in parallel to the vibration measurement cable to be tested;

[0040] One end of the piezoelectric vibration sensor is connected to the vibration calibration system, and the other end is connected to the charge acquisition system;

[0041] The charge acquisition system is used to collect the total charge at its location;

[0042] Both standard capacitive and piezoelectric vibration sensors are connected in parallel with the vibration measurement cable to be tested.

[0043] In this embodiment, the total capacitance of the vibration measurement cable includes parasitic capacitance and distributed capacitance. Normally, the parasitic capacitance of a vibration measurement cable is very small and negligible. However, for some lower-performance vibration measurement cables, the parasitic capacitance is very large. This causes the cable insulation to be shaken, charging the parasitic capacitance and resulting in a higher zero-point noise value when the cable is connected to the acquisition system, sometimes even exceeding the test signal value. The specific impact on the test vibration signal is analyzed as follows:

[0044] Let the parasitic capacitance of the vibration measurement cable to be tested be C. j The distributed capacitance of the vibration measurement cable to be tested is C.f C j and C f Since the connections are in parallel, the total capacitance C1 of the vibration measurement cable to be tested is: C1 = C j +C f Since the physical quantity measured by vibration is electric charge, let the total charge of the vibration measurement cable to be tested be q0, and the charge of the distributed capacitance of the vibration measurement cable to be tested be q2. Then, due to the existence of parasitic capacitance, some charge will accumulate on it. Let the charge of the parasitic capacitance of the vibration measurement cable to be tested be q3. According to the conservation formula, we can get: q0=q2+q3;

[0045] Therefore, due to the presence of parasitic capacitance, a portion of the charge generated by vibration during the test is absorbed by the parasitic capacitance, resulting in a lower measured charge and affecting the accuracy of the vibration measurement data. Thus, the parasitic capacitance of this type of vibration measurement cable must be eliminated.

[0046] Based on the existence of the aforementioned parasitic capacitance, the unloaded load value for the charge acquisition system is 2.3 × 10⁻⁶. -3 m / s 2 If the acceleration is such that its equivalent charge is 2.3 × 10⁻⁶, then its equivalent charge is 2.3 × 10⁻⁶. -3 pC (acceleration value: equivalent charge value = 1m / s²) 2 (1 pC). By connecting the vibration measurement cable to be tested, the equivalent charge value measured ranges from 30 to 80 pC. The reason for the change in charge is the presence of noise voltage in the cable.

[0047] Based on the above analysis, this embodiment presents a reliability testing method for vibration measurement cables, using a reliability testing system for vibration measurement cables, the model of which is shown in Figure 2; specifically, it includes the following steps:

[0048] S1. Measure the length of the vibration measurement cable to be tested and calculate the distributed capacitance value C of the vibration measurement cable to be tested. f Simultaneously, the vibration measurement cable to be tested is connected in parallel to a standard capacitor;

[0049] S2. Remove the piezoelectric vibration sensor, apply a standard known voltage U through the vibration calibration system, and collect the total charge q of the standard capacitor and the vibration measurement cable to be tested through the charge acquisition system. Combine the standard known voltage U and the capacitance value C of the standard capacitor to calculate the total capacitance value C1 of the vibration measurement cable to be tested. The formula is: q=(C1+C)×U.

[0050] Figure 3 shows the waveform of a known voltage signal vibrating at 1kHz and 8V during normal operation; Figure 4 shows the waveform of a known voltage signal vibrating at 78.125Hz and 1.2V during low-frequency operation.

[0051] A standard known voltage signal is applied to the vibration calibration system for normal vibration at 1kHz and 8V. The capacitance value of the standard capacitor is C = 1000pF. The measured value of q is 12000pC, and C1 = 500pF is obtained.

[0052] The calculation method was verified as follows:

[0053] The standard known voltage signal was adjusted to a low-frequency vibration of 78.125Hz and 1.2V. By substituting C and C1 into the value, the output q = 1800pC was obtained. By recording the waveform value of the charge acquisition system, the measured q was 1790pC, which is consistent with the calculated result.

[0054] S3. Reconnect the piezoelectric vibration sensor, remove the standard capacitor, remove the standard known voltage U, and then apply the rated voltage u to the piezoelectric vibration sensor. Collect the total charge Q of the piezoelectric vibration sensor and the vibration measurement cable to be tested through the charge acquisition system.

[0055] S4. Based on the total capacitance value C1 of the vibration measurement cable to be tested in S2 and the distributed capacitance value C of the vibration measurement cable to be tested in S1... f Calculate the parasitic capacitance C of the vibration measurement cable to be tested. j ;

[0056] S5. Calculate the charge q1 of the piezoelectric vibration sensor based on the rated voltage u and the capacitance of the piezoelectric vibration sensor; calculate the charge q1 of the piezoelectric vibration sensor based on the rated voltage u and the distributed capacitance C of the vibration measurement cable to be detected in S1. f Calculate the distributed capacitance charge q2 of the vibration measurement cable to be tested;

[0057] S6. Based on the total charge Q of the piezoelectric vibration sensor and the vibration measurement cable to be tested in S3, and the charge q1 of the piezoelectric vibration sensor and the distributed capacitance charge q2 of the vibration measurement cable to be tested in S5, calculate the charge q3 accumulated by the parasitic capacitance of the cable; the formula is: q3=Q-q1-q2.

[0058] S7, combined with the parasitic capacitance value C of the vibration measurement cable to be detected in S4. j Calculate the cable noise voltage U based on the charge q3 accumulated by the cable parasitic capacitance in S6. 噪 The formula is: U 噪 =q3 / C j .

[0059] S8. Collect the output voltage of the piezoelectric vibration sensor and calculate the cable noise voltage U. 噪 The reliability of the vibration measurement cable under test is good when the ratio of the vibration measurement cable to the output voltage of the piezoelectric vibration sensor is not greater than 5%; otherwise, the reliability of the vibration measurement cable under test is poor.

[0060] When selecting and using vibration measurement cables, choose cables with a low ratio of cable noise voltage to the standard known voltage signal, as these cables have the advantage of low noise.

[0061] This invention offers advantages such as fast detection speed and good detection effect in the reliability testing of vibration cables. It determines reliability by calculating the cable noise voltage, which facilitates the selection and use of vibration measurement cables and avoids the problem of excessive noise voltage affecting the accuracy of data measurement after the vibration measurement cable has been laid and connected to the vibration sensor.

[0062] The above description is merely a specific embodiment of the present invention and a comparison of the effects of the specific embodiments with relevant comparative examples. However, the scope of protection of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present invention should be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A reliability testing system for vibration measurement cables, characterized in that: This includes a vibration calibration system, a standard capacitor, a charge acquisition system, and a piezoelectric vibration sensor; The output of the vibration calibration system is connected to one end of a standard capacitor to load a standard known voltage signal. The other end of the standard capacitor is connected to a charge acquisition system; One end of the piezoelectric vibration sensor is connected to the vibration calibration system, and the other end is connected to the charge acquisition system; The charge acquisition system is used to collect the total charge at the location; The standard capacitor and piezoelectric vibration sensors are connected in parallel with the vibration measurement cable to be tested.

2. The reliability testing system for a vibration measurement cable according to claim 1, characterized in that: The standard known voltage signal is a sinusoidal signal, with a frequency of 1000Hz and a voltage of 8V during normal vibration, and a frequency of 78.125Hz and a voltage of 1.2V during low-frequency vibration.

3. The reliability testing system for a vibration measurement cable according to claim 1, characterized in that: The standard capacitor has a capacitance value of 500pF, 1000pF, 1500pF, or 2000pF.

4. A method for reliability testing of a vibration measuring cable, using the reliability testing system for a vibration measuring cable as described in any one of claims 1-3, characterized in that, Includes the following steps: S1. Measure the length of the vibration measurement cable to be tested and calculate the distributed capacitance value C of the vibration measurement cable to be tested. f Simultaneously, the vibration measurement cable to be tested is connected in parallel to a standard capacitor; S2. Remove the piezoelectric vibration sensor, apply a standard known voltage U through the vibration calibration system, and collect the total charge q of the standard capacitor and the vibration measurement cable to be tested through the charge acquisition system. Combine the standard known voltage U and the capacitance value C of the standard capacitor to calculate the total capacitance value C1 of the vibration measurement cable to be tested. S3. Reconnect the piezoelectric vibration sensor, remove the standard capacitor, remove the standard known voltage U, and then apply the rated voltage u to the piezoelectric vibration sensor. Collect the total charge Q of the piezoelectric vibration sensor and the vibration measurement cable to be tested through the charge acquisition system. S4. Based on the total capacitance value C1 of the vibration measurement cable to be tested in S2 and the distributed capacitance value C of the vibration measurement cable to be tested in S1... f Calculate the parasitic capacitance C of the vibration measurement cable to be tested. j ; S5. Calculate the charge q1 of the piezoelectric vibration sensor based on the rated voltage u and the capacitance of the piezoelectric vibration sensor; calculate the charge q1 of the piezoelectric vibration sensor based on the rated voltage u and the distributed capacitance C of the vibration measurement cable to be detected in S1. f Calculate the distributed capacitance charge q2 of the vibration measurement cable to be tested; S6. Based on the total charge Q of the piezoelectric vibration sensor and the vibration measurement cable to be tested in S3, and the charge q1 of the piezoelectric vibration sensor and the distributed capacitance charge q2 of the vibration measurement cable to be tested in S5, calculate the charge q3 of the cable parasitic capacitance accumulation. S7, combined with the parasitic capacitance value C of the vibration measurement cable to be detected in S4. j Calculate the cable noise voltage U based on the charge q3 accumulated by the cable parasitic capacitance in S6. 噪 ; S8. Collect the output voltage of the piezoelectric vibration sensor and calculate the cable noise voltage U. 噪 The reliability of the vibration measurement cable under test is good when the ratio of the vibration measurement cable to the output voltage of the piezoelectric vibration sensor is not greater than 5%; otherwise, the reliability of the vibration measurement cable under test is poor.

5. The reliability testing method for a vibration measurement cable according to claim 4, characterized in that, The formula for calculating the total capacitance C1 of the vibration measurement cable to be tested, as described in S2, is: q=(C1+C)×U.

6. The reliability testing method for a vibration measurement cable according to claim 4, characterized in that, The formula for calculating the charge q3 accumulated by the parasitic capacitance of the cable as described in S6 is: q3=Q-q1-q2.

7. The reliability testing method for a vibration measurement cable according to claim 4, characterized in that, The calculation of cable noise voltage U is described in S7. 噪 The formula is: U 噪 =q3 / C j .

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