A Testing Method for the Output Impedance of a Two-Wire IEPE Sensor

Abstract

The present invention provides a method for testing the output impedance of a two-wire IEPE sensor. The two-wire IEPE sensor to be measured is connected in parallel with a rheostat box, and then connected in series with a constant current module and powered by a DC regulated power supply. After the sensor to be measured is powered on, the rheostat box acts as a load. By changing the resistance value of the rheostat box multiple times, the load impedance is changed. At the same time, the current value flowing through the sensor to be measured and the voltage value across the sensor to be measured are detected and recorded. Then, N impedance values are calculated through the output impedance calculation formula, and the average value of the N impedance values is obtained to get the final output impedance value of the sensor to be measured. The power supply equipment and detection device adopted in the present invention only include a rheostat box, a DC regulated power supply, an ammeter, a voltmeter, a constant current module and connecting wires, which are very easy to obtain, and the test is simple, with low calculation amount and high efficiency.

Description

Technical Field

[0001] The present invention relates to a method for testing parameters of a two-wire IEPE sensor, specifically, a method for testing the output impedance of a two-wire IEPE sensor. Background Art

[0002] Currently, domestic two-wire IEPE sensors with built-in integrated circuit boards have requirements for output impedance. However, for the output impedance of two-wire IEPE sensors, each sensor manufacturer does not have a unified test standard or test method. But some manufacturers will use the traditional method of testing the AC output amplitude, for example: using the test method of the output impedance of an operational amplifier circuit: providing an excitation signal through devices such as a function signal generator or a vibration table, and measuring the output signal of the product at the output end of the test product in the no-load state or the state of being shunted with a variable resistor box through a collection device or an oscilloscope, and recording them as V 0 (no-load) and V 0 (load). When V 0 (load) = V 0 (no-load) / 2, V 0 (load) is the output impedance of the product. However, this method requires precision equipment such as a function signal generator or a vibration table, a collection device or an oscilloscope. The test equipment is relatively expensive and the cost is high. Moreover, this method is more suitable for three-wire or four-wire sensors powered by non-constant current sources and is not applicable to the test of the output impedance of two-wire IEPE sensors.

[0003] It can be seen that for the output impedance index of two-wire IEPE sensors, there is a lack of a convenient, fast, accurate and effective test method, which may lead to poor matching between two-wire IEPE sensors and data acquisition devices. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a method for testing the output impedance of a two-wire IEPE sensor, which uses the method of testing the DC current value and voltage value to replace the traditional method of testing the AC output amplitude, and is more suitable for the test of the output impedance of IEPE sensors.

[0005] To achieve the foregoing invention purpose, the technical solution adopted in the embodiment of the present invention is: a method for testing the output impedance of a two-wire IEPE sensor, including:

[0006] Connect the two-wire IEPE sensor to be tested in parallel with a variable resistor box and then connect it in series with a constant current module, and supply power by a DC regulated power supply. Connect an ammeter in series on the branch of the two-wire IEPE sensor to be tested, and connect a voltmeter in parallel across the two ends of the two-wire IEPE sensor to be tested;

[0007] First, adjust the value of the rheostat to a relatively large resistance value so that the reading of the ammeter is close to the current output value of the constant current module, and record the reading of the voltmeter as the initial value U. 0 , and record the reading of the ammeter as the initial value I. 0 , then gradually reduce the resistance value of the rheostat. Each time the rheostat is adjusted by one resistance value, record the reading of the voltmeter and the reading of the ammeter. When the reading of the ammeter is less than the minimum operating current of the measured two-wire IEPE sensor, stop recording the values of the voltmeter and the ammeter, and the test is over. At this time, a total of n readings of the voltmeter U 0 , U 1 , U 2 , …U N and n readings of the ammeter I 0 , I 1 , I 2 , …I N ;

[0008] Calculate N impedance values according to the impedance calculation formula for all the voltmeter readings and ammeter readings, where N = n - 1; then calculate the average value of the N impedance values, and this average value is the output impedance R of the measured two-wire IEPE sensor. 0 .

[0009] The calculation formula for the N impedance values R N is:

[0010]

[0011] N = 1, 2, 3…n - 1, and calculate N impedance values R 1 , R 2 , R 3 , …R N ;

[0012] The calculation formula for the output impedance R 0 is respectively:

[0013]

[0014] Further, the adjustment of the rheostat is a uniform adjustment, that is, each time it is adjusted downward by one step value;

[0015] When the resistance value range of the rheostat is 100 kΩ - 1 MΩ, the step value of the adjustment is 300 kΩ;

[0016] When the resistance value range of the rheostat is 10 kΩ - 100 kΩ, the step value of the adjustment is 30 kΩ,

[0017] When the resistance value range of the rheostat is 1 kΩ - 10 kΩ, the step value of the adjustment is 1 kΩ.

[0018] Furthermore, the maximum power supply voltage of the DC regulated power supply is not less than 20V DC ;

[0019] The constant current module is a "voltage - current" conversion module;

[0020] The voltmeter is a multimeter with a V range, used to measure the DC voltage value;

[0021] The ammeter is a multimeter with an mA range, used to measure the DC current value.

[0022] The advantages of the present invention are as follows: The present invention uses the method of testing DC current values and voltage values to replace the traditional method of testing AC output amplitudes, which is more suitable for testing the output impedance of IEPE sensors. Specifically, the two - wire IEPE sensor to be measured is connected in parallel with a rheostat, and then connected in series with a constant current module, and powered by a DC regulated power supply. After the sensor to be measured is powered on, the rheostat undertakes the load function. By changing the resistance value of the rheostat multiple times, the load impedance changes. At this time, the readings in the voltmeter and ammeter will also change accordingly. At the same time, the current value flowing through the sensor to be measured and the voltage value across the sensor to be measured are detected and recorded. Then, N impedance values are calculated through the output impedance calculation formula, and the average value of the N impedance values is obtained to get the final output impedance value of the sensor to be measured. The power supply equipment and detection device adopted in the present invention only include a rheostat, a DC regulated power supply, an ammeter, a voltmeter, a constant current module and connecting wires, which are very easy to obtain, and the test is simple, with a low calculation amount and high efficiency. Description of the Drawings

[0023] The following further describes the present invention with reference to the drawings in conjunction with embodiments.

[0024] Figure 1 It is a schematic diagram of the circuit connection structure of the power supply equipment, detection device of the present invention and the sensor to be measured.

[0025] Figure 2 It is a table for impedance calculation of the present invention. Specific Embodiments

[0026] The embodiment of the present invention provides a method for testing the output impedance of a two - wire IEPE sensor. By using the method of testing DC current values and voltage values to replace the traditional method of testing AC output amplitudes, it is more suitable for testing the output impedance of IEPE sensors.

[0027] The technical solutions in the embodiments of the present invention to solve the above problems are generally as follows: The present invention adopts the method of measuring the DC current value and voltage value. Specifically, the two-wire IEPE sensor to be measured is connected in parallel with a rheostat box, and then connected in series with a constant current module, and powered by a DC regulated power supply. After the sensor to be measured is energized, the rheostat box undertakes the load function. By changing the resistance value of the rheostat box multiple times, the load impedance changes. At this time, the readings in the voltmeter and ammeter also change. At the same time, the current value flowing through the sensor to be measured and the voltage value across the sensor to be measured are detected and recorded, and then N impedance values are calculated through the output impedance calculation formula, and the average value of the N impedance values is obtained to get the final output impedance value of the sensor to be measured.

[0028] To better understand the above technical solutions, the above technical solutions will be described in detail below in conjunction with the accompanying drawings of the specification and specific embodiments.

[0029] Please refer to Figure 1 As shown, a method for measuring the output impedance of a two-wire IEPE sensor in this embodiment includes:

[0030] The two-wire IEPE sensor 1 to be measured is connected in parallel with a rheostat box 2 and then connected in series with a constant current module 3, and is powered by a DC regulated power supply 4. An ammeter 5 is connected in series on the branch of the two-wire IEPE sensor 1 to be measured, and a voltmeter 6 is connected in parallel across the two-wire IEPE sensor 1 to be measured;

[0031] Adjust the resistance value of the rheostat box 2 to change the load impedance. At this time, the readings in the voltmeter 6 and ammeter 5 will also change. The adjustment process is as follows:

[0032] First, adjust the value of the rheostat box 2 to a relatively large resistance value RT 0 , so that the reading of the ammeter 5 is close to the current output value of the constant current module 3, the reading of the voltmeter 6 is recorded as the initial value U 0 , and the reading of the ammeter 5 is recorded as the initial value I 0 . Then, gradually reduce the resistance value RT of the rheostat box 2. Each time the rheostat box 2 is adjusted by a resistance value RT, the reading of the voltmeter 6 and the reading of the ammeter 5 are recorded once. When the reading of the ammeter 5 is less than the minimum operating current of the two-wire IEPE sensor 1 to be measured, it means that the current flowing through the IEPE sensor is insufficient, so that the IEPE sensor cannot work normally. At this time, the measured voltage value and current value are not valid data. Therefore, the values of the voltmeter 6 and ammeter 5 are no longer recorded, and the test work ends at this time. For example, if the minimum operating current of the sensor is 2 mA, the test ends when the reading of the ammeter is less than 2 mA, and the current value less than 2 mA is not recorded. Suppose a total of n readings of the voltmeter U 0 、U 1, U 2 , …U N and the readings I 0 , I 1 , I 2 , …I N ;

[0033] Calculate N impedance values according to the impedance calculation formula from all the voltmeter readings and ammeter readings, where N = n - 1; then calculate the average value of the N impedance values, and this average value is the output impedance R of the two-wire IEPE sensor 0 .

[0034] The calculation formula for the N impedance values R N is as follows:

[0035]

[0036] N = 1, 2, 3…n - 1, and calculate N impedance values R 1 , R 2 , R 3 , …R N ;

[0037] Substitute the N impedance values R 1 , R 2 , R 3 , …R N into the following calculation formula for the output impedance R 0 to calculate the output impedance R of the two-wire IEPE sensor 0 :

[0038]

[0039] Among them, as a more optimal or more specific implementation manner of this embodiment, the adjustment of the rheostat is a uniform adjustment, that is, each time it is adjusted downward by one step value; generally, the output impedance of the IEPE sensor is less than 1 kΩ or even less than 100 Ω. When testing, the resistance value range of the rheostat 2 is from 1 kΩ to 10 kΩ to obtain a current value less than the minimum operating current. Therefore, the step value setting in the 1 kΩ - 10 kΩ section is relatively small, and the step value settings in the 10 kΩ - 100 kΩ and 100 kΩ - 1 MΩ sections are relatively large. For example:

[0040] When the rheostat 2 is adjusted in the 100 kΩ - 1 MΩ resistance value section, the adjusted step value can be set to 300 kΩ;

[0041] When the rheostat 2 is adjusted in the 10 kΩ - 100 kΩ resistance value section, the adjusted step value can be set to 30 kΩ,

[0042] When the resistance box 2 is adjusted in the resistance range of 1 kΩ - 10 kΩ, the step value of adjustment can be set to 1 kΩ.

[0043] The maximum supply voltage of the DC regulated power supply 4 is generally not less than 20V DC ; The static operating point voltage value of the IEPE sensor is generally 10 - 14V DC , and a few will reach 16V DC , therefore, generally the supply voltage is set not less than 20V CC .

[0044] The constant current module 3 is a "voltage - current" conversion module;

[0045] The voltmeter 6 is a multimeter with a V range, used to measure the DC voltage value;

[0046] The ammeter 5 is a multimeter with an mA range, used to measure the DC current value.

[0047] As Figure 2 shown, when recording, a table can be designed for convenient recording, so as to record the initial values of the resistance box 2, the voltmeter 6, and the ammeter 5, the resistance value of the resistance box after each adjustment, the readings of the voltmeter 6 and the ammeter 5, and the N impedance values R 1 , R 2 , R 3 , …R 2 .

[0048] In the present invention, the two - wire IEPE sensor to be measured is connected in parallel with the resistance box, then connected in series with the constant current module, and powered by the DC regulated power supply. After the measured sensor is powered on, the resistance box undertakes the load function. By changing the resistance value of the resistance box multiple times, the load impedance changes. At this time, the readings in the voltmeter and the ammeter will also change accordingly. At the same time, the current value flowing through the measured sensor and the voltage value across the measured sensor are detected and recorded. Then, through the output impedance calculation formula, N impedance values are calculated, and the average value of the N impedance values is obtained to get the final output impedance value of the measured sensor.

[0049] Although the specific implementation manners of the present invention are described above, those skilled in the art should understand that the specific embodiments we described are illustrative rather than used to limit the scope of the present invention. Equivalent modifications and variations made by those skilled in the art in accordance with the spirit of the present invention should all be covered within the scope protected by the claims of the present invention.

Claims

1. A test method for the output impedance of a two-wire IEPE sensor, characterized in that: it includes the following process: The two-wire IEPE sensor to be tested is connected in parallel with a variable resistor box and then connected in series with a constant current module, and is powered by a DC regulated power supply. An ammeter is connected in series on the branch of the two-wire IEPE sensor to be tested, and a voltmeter is connected in parallel across the two ends of the two-wire IEPE sensor to be tested; First, adjust the value of the rheostat to a relatively large resistance value so that the reading of the ammeter is close to the current output value of the constant current module, and record the reading of the voltmeter as the initial value U 0 , and record the reading of the ammeter as the initial value I 0 . Then, gradually decrease the resistance value of the rheostat. Each time the rheostat is adjusted by one resistance value, record the reading of the voltmeter and the reading of the ammeter. When the reading of the ammeter is less than the minimum operating current of the two-wire IEPE sensor under test, stop recording the values of the voltmeter and the ammeter, and the test is over. At this time, a total of n readings of the voltmeter U 0 , U 1 , U 2 , …U N and n readings of the ammeter I 0 , I 1 , I 2 , …I N ; Calculate N impedance values according to the impedance calculation formula based on all the voltmeter readings and ammeter readings, where N = n - 1; then calculate the average value of the N impedance values, and this average value is the output impedance R of the measured two-wire IEPE sensor 0 .

2. The test method for the output impedance of a two-wire IEPE sensor according to claim 1, characterized in that: The N impedance values R N are calculated by the following formula: N = 1, 2, 3…n - 1, and N impedance values R are calculated through the formula 1 1 , R 2 , R 3 , …R n ; The output impedance R 0 has the following calculation formulas respectively:

3. The test method for the output impedance of a two-wire IEPE sensor according to claim 1, characterized in that: The adjustment of the variable resistor box is a uniform adjustment, that is, each time it is adjusted downward by one step value; When the resistance value range of the variable resistor box is 100 kΩ - 1 MΩ, the step value of adjustment is 300 kΩ; When the resistance value range of the variable resistor box is 10 kΩ - 100 kΩ, the step value of adjustment is 30 kΩ, When the resistance value range of the variable resistor box is 1 kΩ - 10 kΩ, the step value of adjustment is 1 kΩ.

4. The test method for the output impedance of a two-wire IEPE sensor according to claim 1, characterized in that: The maximum supply voltage of the DC regulated power supply is not less than 20V DC ; The constant current module is a "voltage - current" conversion module; The voltmeter is a multimeter with a V range, used to measure the DC voltage value; The ammeter is a multimeter with an mA range, used to measure the DC current value.

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