CN110568221B - Device and method for testing sensitivity of accelerometer - Google Patents
Device and method for testing sensitivity of accelerometer Download PDFInfo
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- CN110568221B CN110568221B CN201910757111.XA CN201910757111A CN110568221B CN 110568221 B CN110568221 B CN 110568221B CN 201910757111 A CN201910757111 A CN 201910757111A CN 110568221 B CN110568221 B CN 110568221B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
- G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
- G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P21/00—Testing or calibrating of apparatus or devices covered by the preceding groups
Abstract
The invention provides a device for testing the sensitivity of an accelerometer, which comprises a metal frame, wherein a fixed sliding ring is arranged at the top end of the metal frame, a thin wire penetrates through the fixed sliding ring, one end of the thin wire is connected with the top end of a metal rod through a micro ring, a notch is processed in the middle of the metal rod, the accelerometer and a strain gauge to be tested are installed on the notch, the accelerometer and the strain gauge to be tested are connected with an amplifier, and the amplifier is connected with a computer. The invention also provides a test method. The testing device is based on the strain gauge and the free drop bar impact method, the equipment is convenient to operate and use, the speed can be accurately obtained, and the testing precision of the sensitivity of the accelerometer can be obviously improved; in addition, the notch of the testing device for the sensitivity of the impact type accelerometer is processed in the middle of the metal rod instead of two free ends, so that the testing device is more suitable for the installation and the test of the plane sticking type accelerometer or the installation test of the flat type accelerometer.
Description
Technical Field
The invention relates to the technical field of mechanical test analysis of microsensors, in particular to a device and a method for testing the sensitivity of an accelerometer.
Background
The Micro Electro Mechanical System (MEMS) processing technology is mature on the preparation of micro-nano devices. Such as a silicon micro-accelerometer, which has the characteristics of small volume, light weight, easy integration, excellent mechanical property and quick response. The high-range silicon micro piezoresistive accelerometer can quickly respond and resist high-strength transient impact, has the function of detecting acceleration or speed, has the functions of a threshold and a switch, and is applied to the field of vibration and impact detection analysis. The sensitivity of a high-impact accelerometer is an important parameter to measure for characterization.
The sensitivity of high impact accelerometers is very small, requiring high impact equipment to do soAnd a larger pulse signal is provided to extract parameters such as sensitivity. The sensitivity of an accelerometer is defined as the ratio of the output voltage of the accelerometer to the input acceleration at a certain operating voltage. For a high impact accelerometer, the unit of sensitivity is expressed as: mu V/g/U0Or simply μ V/g, where μ V is the unit of voltage, microvolts; u shape0Is the voltage, typically volts, applied across the sensor bridge; g is gravity acceleration, 1g is 9.8m/s2. Conventional testing means, such as vibration measurement of a vibration table, static measurement of a centrifuge, and the like, are difficult to meet. Transient high impact testing methods such as the free drop bar method, the drop hammer method, the dynamic Hopkinson test method, and the like can fulfill this requirement. For example, the free fall rod method can achieve 5000g to 2 kg (g, 1g ═ 9.8 m/s)2) Testing of (2); a speed measurement method based on laser Doppler and a strain gauge, namely a Hopkinson method, can realize measuring range test of 1-10-even more than 20-ten thousand g. However, the Hopkinson test equipment is complex and expensive, and the operation is not very simple. Therefore, a simple method for testing the sensitivity and other parameters of the accelerometer is needed.
The free rod falling impact method is a simple and direct accelerometer sensitivity dynamic impact test method. The principle is as follows: the metal rod vertically and freely falls, one end of the metal rod is positively collided with a hard metal anvil placed on the ground, the speed change generated in the collision time is used for calculating the generated acceleration, and instantaneous acceleration of about thousands to 2 thousands g is generated in tens of microseconds; meanwhile, an accelerometer fixed on the metal rod senses impact and outputs a voltage signal. And integrating the main wave signal of the voltage pulse of the accelerometer and dividing the integrated signal by the speed change to obtain the sensitivity of the accelerometer. As a preliminary test method, the free-fall height of the metal rod is used to calculate the initial speed of the metal rod colliding with the metal anvil, i.e., the centroid speed Vc，(
h is the drop height) is also the overall velocity of the rod, and likewise the metal rod bounce height is used to calculate the initial velocity of the bounce. In general, the free-fall method calculates the sensitivity of the accelerometer using the velocity change of the metal bar as an input, as described in the Endevco reference TP321 "Acceleration levels of dropped objects".
From the theory of stress wave transmission in solids, it can be known that the free fall of a metal rod collides with a metal anvil placed on the ground to generate strain and a corresponding compressive stress wave, and within the elastic limit of the metal, the stress wave propagates along the metal rod at the speed of sound c, and the particle velocity at any position except the free end in the metal rod is VpC epsilon, where epsilon is the strain (stress wave in solids h. coulski, science press, 1958). That is, the actual velocity at any location in the metal rod (the mass point at any location) is the product of the speed of sound in the metal rod and the strain at that location. In the Hopkinson method, which is based on a strain gauge, the velocity or acceleration of an input is generally calculated using this velocity as a standard.
However, theory and experiment show that in the free drop rod method, the mass center velocity V of the free falling body of the metal rodcOr the overall velocity of the metal rod and the velocity V of the particle transmitted at the velocity of the stress wavepDifferent. Therefore, if the centroid velocity V of the free-fall is directly adoptedcTo calculate the sensitivity of the accelerometer, a certain offset will be generated.
Disclosure of Invention
The invention aims to solve the technical problem of providing a device and a method for testing the sensitivity of a high-range accelerometer, which have the characteristics of large impact acceleration, directness, rapidness, safety, reliability and higher accuracy.
In order to achieve the purpose, the invention provides a device for testing the sensitivity of an accelerometer, which comprises a metal frame, wherein a fixed sliding ring is arranged at the top end of the metal frame, a thin wire penetrates through the fixed sliding ring, one end of the thin wire is connected with the top end of a metal rod through a micro ring, a notch is processed in the middle of the metal rod, an accelerometer to be tested and a strain gauge are installed on the notch, the accelerometer to be tested and the strain gauge are connected with an amplifier, and the amplifier is connected with a computer.
The strain gauge is connected with three external resistors to form a Wheatstone bridge, and is connected with the amplifier through the Wheatstone bridge and a signal wire, one diagonal position of the Wheatstone bridge is connected with one output end of the amplifier, and the other diagonal position of the Wheatstone bridge is connected with one input end of the amplifier.
The three external resistors are fixed resistors with the same resistance specification, and the resistance of the strain gauge is consistent with the resistance of the three external resistors.
The distance between the notch and the top end of the metal rod is one half to three quarters of the total length of the metal rod.
The sensitive direction of the strain gauge is along the axial direction of the metal rod.
The notch is provided with a smooth plane parallel to the axial direction of the metal rod, and the accelerometer to be tested and the strain gauge are installed on the plane of the notch.
The length of the metal rod is 1.0-1.5 m, the diameter is 16-20 mm, the length of the notch is 2-3 cm, the depth is 1-2 mm, and the width is 9-12 mm.
And a metal anvil is arranged on the base of the metal frame, and the metal rod is positioned right above the metal anvil.
The metal rod is sleeved with at least one protection ring fixed on the metal frame through a connecting beam.
In another aspect, the present invention provides a method for testing the sensitivity of an impact type accelerometer, including:
step S1: the method comprises the steps of constructing a testing device of the sensitivity of an impact type accelerometer, comprising a metal frame, wherein a fixed slip ring is arranged at the top end of the metal frame, a thin wire penetrates through the fixed slip ring, one end of the thin wire is connected with the top end of a metal rod through a micro ring, a notch is processed in the middle of the metal rod, an accelerometer to be tested and a strain gauge are installed on the notch, the accelerometer to be tested and the strain gauge are connected with an amplifier, and the amplifier is connected with a computer;
step S2: starting and setting a computer;
step S3: lifting the metal rod to a certain height by adopting the thin wire, and releasing the metal rod;
step S4: recording the output voltage of the strain gauge and the output voltage of the accelerometer to be tested by using a computer;
step S5: calculating the strain of the metal lever from the maximum value of the output voltage of the strain gauge in step S4;
step S6: integrating the output voltage signal of the accelerometer to be tested in the step S4;
step S7: and obtaining the sensitivity of the accelerometer to be tested according to the strain of the metal rod and the integral calculation result of the output voltage signal of the accelerometer to be tested in the step S5.
The sensitivity of the accelerometer to be tested is as follows:
wherein the content of the first and second substances,
for the integral calculation of the output voltage signal of the accelerometer under test, Ua(t) is the output voltage signal of the accelerometer to be measured, the unit is μ V, t is time, the unit is S, S is the sensitivity of the accelerometer to be measured, A is the amplification factor of the amplifier, c is the sound velocity transmitted by the pulse wave in the metal rod, the unit is m/S, and epsilon is the strain of the metal rod.
The device for testing the sensitivity of the impact type accelerometer is based on the strain gauge and the free falling rod impact method, utilizes the higher impact acceleration generated by the collision of the free falling body of the metal rod as an excitation source, is convenient to operate and use, and utilizes the strain gauge as a method for detecting the in-situ speed of the accelerometer, thereby realizing the reliable extraction of the sensitivity parameters of the accelerometer, obtaining the speed more accurately, obviously improving the testing precision of the sensitivity of the accelerometer, and having the characteristics of simplicity, practicability and more accuracy; in addition, the notch of the testing device for the sensitivity of the impact type accelerometer is processed in the middle of the metal rod instead of two free ends, so that the testing device is more suitable for the installation and the test of the plane sticking type accelerometer or the installation test of the flat type accelerometer.
Drawings
Fig. 1 is a schematic structural diagram of an overall test device for sensitivity of an accelerometer according to an embodiment of the invention.
Fig. 2 is a schematic structural diagram of a metal bar of the apparatus for testing the sensitivity of an accelerometer shown in fig. 1.
Fig. 3 is a schematic diagram of a wheatstone bridge of the accelerometer sensitivity testing apparatus shown in fig. 1.
Fig. 4 is a schematic diagram of the wheatstone bridge of the accelerometer sensitivity testing device shown in fig. 1 and the connection of the accelerometer to be tested to the amplifier.
FIG. 5 is a graph of the output voltage waveform of an accelerometer and strain gauge at a 20cm drop height.
In the figure:
1. a metal frame; 11. a metal anvil; 12. fixing a slip ring; 2. a thin wire; 3. a metal rod; 31. a recess; 4. a micro-ring; 5. an accelerometer to be tested; 6. a strain gauge; 61. connecting a resistor externally; 7. an amplifier; 8. a computer; 9. a guard ring; H. a wheatstone bridge.
Detailed Description
The invention will be further illustrated with reference to the following specific examples. The examples are intended to illustrate the invention only and are not intended to limit the scope of the invention. Further, it should be understood that various changes or modifications can be made by those skilled in the art after reading the contents of the present invention, and those equivalents also fall within the scope of the invention defined by the appended claims.
Fig. 1 shows a device for testing the sensitivity of an accelerometer according to an embodiment of the present invention, which includes a metal frame 1, a metal anvil 11 is disposed on a base of the metal frame 1, and a fixed slip ring 12 is disposed on a top end of the metal frame 1, a thin wire 2 passes through the fixed slip ring 12, and one end of the thin wire 2 is connected to a top end of a metal rod 3 through a micro-ring 4, and the metal rod 3 is located right above the metal anvil 11. Thereby, the thin wire 2 canSo as to lift the metal rod 3 to a certain height and release the metal rod 3 after stabilization. The metal rod 3 freely falls from a certain height vertical to the ground and collides with a metal anvil 11 arranged on the ground to instantaneously generate a high impact acceleration to form an approximately semi-sinusoidal pulse stress wave with the duration time t0The metal rod falls freely from a certain height h and collides with the metal anvil at the collision speed of
The rebound speed is determined by the rebound height, and freely falls to the rebound process, and the speed direction changes. The faster the speed change in the pulse time, the greater the acceleration, and the acceleration a becomes Δ v/Δ t. The metal rod 3 is sleeved with at least one protection ring 9 fixed on the metal frame 1 through a connecting beam. In the present embodiment, the number of guard rings 9 is 3. The protective ring 9 is used to fixedly hold the metal rod 3 in a vertical direction so as to be fixed within the protective ring 9 after a free fall collision.
As shown in fig. 2, the metal rod 3 is an equiaxial elongated cylindrical metal rod made of aluminum alloy or steel material, has a length of 1.5m-2.0m and a diameter of 16mm-20mm, and is selected to be elongated, so that generated monopulse waves are not superposed on the impulse waves when being reflected from the free end of the metal rod, thereby influencing analysis and calculation. Typically, the pulse width generated by the metal rod colliding with the metal anvil is 50 to 100 microseconds, while the speed of sound in a metal aluminum rod is approximately 5090 m/s. For aluminum alloy rods, the Young's modulus E is 78GPa, and the density rho is 2700 kg/m3And then the sound speed:
the pulses generated in the metal rod then have a wavelength of 0.25m to 0.5m, less than 1 m. Therefore, by using a metal rod having a length of 1m or more than 1m, the generated pulse wave for calculation is not affected by the free end surface reflected wave. The metal rod 3 is provided with a notch 31 in the middle, which notch 31 is located as far away from the top end of the metal rod 3 as possible than from the other end, so that the waves reflected from the end faces and the incident waves do not overlap here. In the present embodimentSaid notch 31 is located at a distance of about one half to three quarters of the total length of the metal rod 3 from the tip of the metal rod, for measuring the acceleration generated by the impact pendulum. The notch 31 has a smooth plane parallel to the axial direction of the metal rod, and a to-be-measured accelerometer 5 and a strain gauge 6 are mounted on the plane of the notch 31 in a clamping or sticking mode. The notch 31 has a length of 2cm to 3cm, a depth of 1mm to 2mm, and a width of 9mm to 12 mm. Wherein, for a metal rod with a radius of 10mm, the notch depth is 1mm, and the notch width is about 8.7mm, approximately 9 mm; if the depth of the notch is 2mm, the width of the notch is 12 mm. It can be estimated that the cross-sectional area of the notch 31 perpendicular to the axial direction of the metal rod is about 10mm2And the circular cross-sectional area of the whole metal rod is 314mm2Then the ratio of the area occupied by the axial cross section of the notch 31 is less than 3%, so that the influence of the cross section of the notch 31 on the reflection of the incident wave is negligible.
Referring to fig. 1 again, the accelerometer 5 and the strain gauge 6 to be measured are connected to an amplifier 7, the strain gauge 6 is a standard foil type (foil type, generally a resistance strain element of copper-nickel or nickel-chromium alloy) strain gauge, the sensitive direction of the strain gauge is along the axial direction of the metal rod 3, the type is KYOWA KFG-1-120-C1-11L1M2R, the resistance is 120.4 ± 0.4 Ω, and the amplifier 7 is preferably a multichannel signal amplifier. Specifically, the strain gauge 6 is connected with three external resistors 61 to form a wheatstone bridge H, and is connected with the amplifier 7 through the wheatstone bridge H and signal lines, and the amplifier 7 is connected with a computer 8 for data acquisition control and processing through the signal lines. Wherein, the computer data acquisition card acquires the frequency of 1.25MHz, and the output bridge voltage of the amplifier 7 is near the working point of 1.65V. Therefore, the strain gauge 6 is attached to the notch 31, the particle velocity of stress wave propagation can be more accurately tested, the stress wave is transmitted to the accelerometer 5 and the strain gauge 6 to be tested after a certain time, the sensors respectively generate corresponding output voltage signals after being impacted, the output voltage signals are output to the computer 8 through the amplifier 7, and the computer 8 synchronously records two waveform signals.
Fig. 3 shows a structure diagram of a wheatstone bridge H composed of a strain gauge 6 and three external resistors 61, wherein the resistor of the strain gauge 6 is Rg which is sensitive to strain, and the three external resistors 61 are fixed resistors with the same resistance specification. The working principle of the strain gauge is as follows: when the strain gauge 6 is fixedly adhered to the metal rod 3 and the metal rod 3 is deformed by an external force, the strain gauge will sense the deformation change, i.e. strain, corresponding to the increase or decrease of its resistance.
The strain ε is expressed as:
ε＝ΔL/L，
where Δ L is the amount of change in length in m, and L is the length in m.
And the change in resistance due to strain is mathematically represented as:
ΔR/R＝Ksε，
wherein R is resistance with unit of omega, and Delta R is resistance change with unit of omega and KsIs the sensitivity factor (dimensionless) of the strain gauge, and ε is the strain.
That is, the gauge sensitivity factor is defined as the ratio of the rate of change of resistance to strain,
wherein the sensitivity factor K of the strain gauge 6sGenerally 2, in the present embodiment, the strain gauge 6 is used with a sensitivity strain factor Ks2.13 ± 1.0%. If strain is 500X 10-6Then the resistance is changed to 2X 500X 10-60.1%, the resistance change is 0.12 Ω for 120 Ω (ohm).
Since the change in resistance of the strain gauge 6 due to strain is very small, a wheatstone bridge H is used to convert the resistance change signal into a voltage change signal. In the wheatstone bridge H, the three external resistors 61 are fixed resistors having the same resistance specification, and the resistance Rg of the strain gauge 6 is the same as the resistances of the three external resistors 61.
Correspondingly, the output voltage U of the Wheatstone bridges(t) is:
wherein, U0Is the supply voltage applied to the Wheatstone bridge in units of V, which in this embodiment is 5V, KsFor the sensitivity factor (dimensionless) of the strain gauge, ε is the strain and A is the signal amplification of amplifier 7, which in this example is 40.
Fig. 4 shows a schematic diagram of the wheatstone bridge H of the accelerometer sensitivity testing device and the connection of the accelerometer 5 to be tested to the amplifier 7, wherein the strain gauge 6 is fixed on the notch 31, the three external resistors 61 are soldered on a printed circuit board outside the metal rod 3, and the three resistors are connected by the elongated wires. One of the diagonals of the wheatstone bridge H is connected to an output of the amplifier 7 for applying a stable voltage, typically 3 to 5 volts, from the power supply provided by the amplifier 7, and the other diagonal is connected to an input of the amplifier 7 for outputting a signal.
Similarly, the accelerometer 5 to be tested as the test target may also be connected to the amplifier 7 through a wheatstone bridge by forming a wheatstone bridge with three external resistors of the accelerometer, or directly connected to the amplifier 7.
Based on the test device for the sensitivity of the accelerometer, the realized test method for the sensitivity of the high-impact accelerometer comprises the following specific steps:
step S1: the device for testing the sensitivity of the accelerometer specifically comprises:
step S11: and (3) mounting and connecting the strain gauge: the strain gauge 6 is mounted and fixed on a notch 31 of the metal rod 3, wherein the sensitive direction of the strain gauge 6 is along the axial direction of the metal rod 3, the strain gauge 6 is connected with three external fixed resistors 31 to form a Wheatstone bridge H, the Wheatstone bridge H is connected with an amplifier 7 by signal lines, and the amplifier 7 is connected with a computer 8 by the signal lines.
Step S12: and (5) mounting and connecting the accelerometer 5 to be tested. An accelerometer 5 to be tested is fixedly arranged on the first notch 31 of the metal rod 3, the sensitive direction of the accelerometer 5 to be tested is along the axial direction of the metal rod 3, the accelerometer 5 to be tested is connected with the amplifier 7 by using a signal wire, and the amplifier 7 is connected with a computer 8 by using a signal wire. The output of the accelerometer 5 to be tested is a voltage signal.
Step S13: the placement of the metal rod 3. As illustrated in fig. 1, the bottom end of the metal rod 3 is inserted into at least one protection ring 9 fixed to a metal frame 1, the bottom end being in contact with, i.e., the end where the collision occurs, a metal anvil 11 on the base of the metal frame 1, and then a wire 2 is connected to a micro-ring 4 on the top end of the metal rod 3, the wire 2 being passed through a fixed slip ring 12.
Step S2: the computer 8 is started and set up. And starting a computer 8 and an amplifier 7, starting a corresponding data acquisition system and display software on the computer 8, and respectively setting software parameters such as sampling threshold voltage, sampling length, display measurement range, working voltage, amplification factor, data acquisition frequency, signal pulse trigger channel and level and the like.
Step S3: lifting the metal rod 3 to a certain height by using the thin wire 2, and releasing the metal rod 3 to perform a free fall impact test of the metal rod 3;
step S4: and (6) data acquisition. The metal rod 3 freely falls down along the rod axis direction and collides with the metal anvil 11 to instantly generate an impact acceleration pulse, a half-sine pressure stress wave is generated on the metal rod 3, the acceleration pulse time is t0 (unit: second, S), the stress wave is transmitted to the strain gauge 6 after a certain time, then the stress wave is transmitted to the accelerometer 5 to be tested, the two sensors of the strain gauge 6 and the accelerometer 5 to be tested respectively output corresponding electric signals to the computer 8 under the impact action, and the computer 8 is adopted to record the output voltage of the strain gauge 6 and the output voltage signal of the accelerometer 5 to be tested.
Thereby, the stress wave formed by the collision of the metal rod 3 with the metal anvil 11 propagates upwards from the bottom of the metal rod 3, the stress wave propagating at an inherent velocity in the metal rod 3 having a circular cross-section. Since both sensors are mounted at the same location, the strain gauge 6 responds in time synchronism with the accelerometer 5 to be measured. Since the wavelength pulse time of the stress wave is short and the length of the metal rod 3 is much longer than the pulse time of the stress wave, the stress wave is generally not dispersed in the metal rod 3.
Step S5: the strain epsilon of the metal lever 3 is calculated from the maximum value of the output voltage u (t) of the strain gauge 6 in step S4. In addition, the strain epsilon of each point is multiplied by the speed c to obtain the speed (c epsilon) of each point, and the acceleration is obtained by differentiating the speed curve with time.
Wherein the strain epsilon of the metal rod 3 is:
where U (t) is the maximum value of the output voltage of strain gauge 6, U0For the supply voltage applied across the Wheatstone bridge H, in units V, KsFor the sensitivity factor of the strain gauge, ε is the strain of the metal rod 3 and A is the signal amplification of the amplifier 7.
In this embodiment, the strain factor at the strain gauge sensitivity employed is Ks2.13 ± 1.0%, the supply voltage U applied to the wheatstone bridge0When the voltage is 5V and the amplification factor A of the signal amplifier is 40 times, the voltage output curve of the strain gauge in the impact collision process is obtained through experimental record, and the maximum voltage U is reads(t) the strain is calculated by substituting the above equation, and the particle velocity of the particle at that point is obtained from the equation as "c ∈". At the speed change time t0The internal acceleration is a, a ═ Δ V/t0＝cε/t0。
Step S6: and integrating the output voltage signal of the accelerometer 5 to be tested in the step S4.
In the free falling collision process of the metal rod 3, the output voltage signal of the first approximate half-sine impact waveform recorded by the accelerometer 5 to be tested is Ua(t)，
Ua(t)＝S×a×A，
Wherein, S is the sensitivity of the accelerometer 5 to be measured, the unit is muV/g/3.3V, wherein 3.3V is the voltage of the voltage stabilizing source of the accelerometer 5 to be measured, a is the acceleration of the top end of the metal rod, the unit is g, A is the amplification factor of the amplifier, and the amplification factor is set to be 20 times (the bandwidth of the amplifier is 10KHz attenuated, and the bandwidth of the amplifier is 17KHz attenuated by 30%).
Thus, at time t0Internally integrating the output voltage signal of the accelerometer 5 to be measured,
wherein Ua (t) is an output voltage signal of the accelerometer 5 to be tested, the unit is muV, t is time, the unit is S, S is the sensitivity of the accelerometer 5 to be tested, the unit is muV/g/3.3V, wherein 3.3V is the voltage stabilizing source voltage of the accelerometer 5 to be tested, a (t) is the acceleration of the top end of the metal rod 3, the unit is g, A is the amplification factor of the amplifier, the amplification factor is set to be 20 times (10% attenuation of 10KHz of the bandwidth of the amplifier and 30% attenuation of 17 KHz), and DeltaV is the integral of the acceleration of the top end of the metal rod 3,
the unit is m/s.
Step S6: and obtaining the sensitivity S of the accelerometer 5 to be measured according to the strain epsilon of the metal rod 3 in the step S5 and the integral calculation result of the output voltage signal of the accelerometer 5 to be measured obtained in the step S6.
The sensitivity of the accelerometer 5 under test is expressed as the ratio of the voltage output of the accelerometer to the input acceleration. The velocity or acceleration of the input is determined from the strain gauge output signal. The sensitivity of the accelerometer 5 to be tested is as follows:
wherein the content of the first and second substances,
for the integral calculation of the output voltage signal of the accelerometer 5 to be measured, Ua(t) is the output voltage signal of the accelerometer 5 to be measured in μ V, t is time in S, S is the sensitivity of the accelerometer 5 to be measured in μ V/g/3.3V, wherein 3.3V is the acceleration to be measuredThe voltage of a voltage stabilizing source of the meter 5A is the amplification factor of the amplifier and is set to be 20 times (the bandwidth of the amplifier is 10KHz attenuated and 30% of 17KHz attenuated), c is the sound velocity transmitted by pulse waves in the metal rod, the unit is m/s, and epsilon is the strain of the metal rod 3.
Results of the experiment
And calculating strain and speed. The maximum output voltages of the strain gauges were 34mV, 39mV and 44mV for drop heights of 15cm, 20cm and 25cm, respectively. It can be seen that the voltage output of the strain gauge is approximately linear with the drop height. The strain was calculated only at 20cm drop height:
for a drop height of 20cm, the corresponding particle velocity VpAnd the metal rod mass center velocity VcThe calculation results are respectively as follows: vp＝cε＝5090×0.366×10-31.862m/s, and the free fall centroid velocity is:
if there is a 5.0% deviation in the speed of the two, then there is a 5.0% deviation in the sensitivity calculation. In fact, if the specific relationship between the metal rod centroid velocity and the particle velocity is known, then the sensitivity calculation based on the drop height can also be obtained by appropriate velocity correction.
And (4) calculating the sensitivity of the accelerometer. For a 20cm drop height, the output peak voltage is 38-42mV, the pulse width is 60-70 mu s, the peak acceleration is positioned between 5000 and 6000g, and the sensitivity of the accelerometer is calculated to be sp0.362 ± 0.008 μ V/g/3.3V. Figure 5 is an output waveform corresponding to the output voltage over time for an accelerometer and strain gauge under test at a 20cm drop height. The accelerometer outputs a nearly half-sinusoidal pulse output waveform, while the strain gauge is changed from the lowest strain to 0 to the highest strain. When the voltage signal output of the strain gauge is maximum, the acceleration voltage signal output of the accelerometer returns to 0 position, and the particle speed measured by the strain gauge reaches the maximum.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and various modifications may be made to the above-described embodiment of the present invention. All simple and equivalent changes and modifications made according to the claims and the content of the specification of the present application fall within the scope of the claims of the present patent application. The invention has not been described in detail in order to avoid obscuring the invention.
Claims (4)
1. A method for testing the sensitivity of an impact type accelerometer is characterized by comprising the following steps:
step S1: the device for testing the sensitivity of the impact type accelerometer comprises a metal frame (1), wherein a fixed sliding ring (12) is arranged at the top end of the metal frame (1), a thin wire (2) penetrates through the fixed sliding ring (12), one end of the thin wire (2) is connected with the top end of a metal rod (3) through a micro-ring (4), a notch (31) is processed in the middle of the metal rod (3), an accelerometer (5) to be tested and a strain gauge (6) are installed on the notch (31), the accelerometer (5) to be tested and the strain gauge (6) are connected with an amplifier (7), and the amplifier (7) is connected with a computer (8);
step S2: starting and setting a computer (8);
step S3: lifting the metal rod (3) to a certain height by adopting the thin wire (2), and releasing the metal rod (3) after stabilization;
step S4: recording the output voltage of the strain gauge (6) and the output voltage of the accelerometer (5) to be tested by using a computer (8);
step S5: calculating the strain of the metal lever (3) from the maximum value of the output voltage of the strain gauge (6) in step S4;
step S6: integrating the output voltage signal of the accelerometer (5) to be tested in the step S4;
step S7: obtaining the sensitivity of the accelerometer (5) to be tested according to the strain of the metal rod (3) and the integral calculation result of the output voltage signal of the accelerometer (5) to be tested in the step S5;
the sensitivity of the accelerometer (5) to be tested is as follows:
wherein the content of the first and second substances,
is the integral calculation result of the output voltage signal of the accelerometer (5) to be measured, UaAnd (t) is an output voltage signal of the accelerometer (5) to be tested, the unit is mu V, t is time, the unit is S, S is the sensitivity of the accelerometer (5) to be tested, A is the amplification factor of the amplifier, c is the sound velocity transmitted by the pulse wave in the metal rod, the unit is m/S, and epsilon is the strain of the metal rod (3).
2. Testing method according to claim 1, characterized in that the recess (31) is at a distance of one half to three quarters of the total length of the metal rod (3) from the top end thereof.
3. A testing method according to claim 1, characterized in that the sensitive direction of the strain gauge (6) is along the axial direction of the metal rod (3), the recess (31) has a smooth plane parallel to the axial direction of the metal rod, and the accelerometer (5) to be tested and the strain gauge (6) are mounted on the plane of the recess (31).
4. The test method according to claim 1, characterized in that the metal rod (3) has a length of 1.0-1.5 m and a diameter of 16-20 mm, and the notch (31) has a length of 2-3 cm, a depth of 1-2 mm and a width of 9-12 mm.
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