CN106124865A - The measuring method of the capacitance of differential capacitance and device - Google Patents
The measuring method of the capacitance of differential capacitance and device Download PDFInfo
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- CN106124865A CN106124865A CN201610794462.4A CN201610794462A CN106124865A CN 106124865 A CN106124865 A CN 106124865A CN 201610794462 A CN201610794462 A CN 201610794462A CN 106124865 A CN106124865 A CN 106124865A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
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Abstract
The present invention provides measuring method and the device of the capacitance of the differential capacitance between a kind of CAN height bit line and CAN low-bit line, the direct-to-ground capacitance of CAN height bit line is equal with the direct-to-ground capacitance of CAN low-bit line, and this measuring method includes: obtain the first capacitance of the direct-to-ground capacitance of CAN height bit line or the first capacitance of the direct-to-ground capacitance of CAN low-bit line；Obtain the capacitance sum of described first capacitance and the second capacitance of differential capacitance；According to described first capacitance and described capacitance sum, determine the second capacitance of differential capacitance；The embodiment of the present invention uses test step by step method to measure the capacitance of differential capacitance；This measuring method is capable of the measurement to differential capacitance and degree of accuracy is higher.
Description
Technical field
The present invention relates to CAN communication technical field, particularly relate to the difference between a kind of CAN height bit line and CAN low-bit line
The measuring method of the capacitance of electric capacity and device.
Background technology
CAN is the abbreviation of controller local area network (Controller Area Network, CAN), and CAN communication is automobile
Communication mode between the widely used controller in field.CAN line is generally divided into CAN_ height bit line (CAN_H line) and CAN_ low level
Line (CAN_L line), can form a differential capacitance C on circuit boards between CAN_H line and CAN_L linediff, CdiffTo CAN_H line
Impact, C is formed with the rising and falling time of CAN_L line and the synchronicity of CAN_H line and CAN_L linediffShould not be too big, typically
Within 100pF.Due to differential capacitance CdiffCapacitance the least, thus to measure bring the biggest difficulty, certainty of measurement
The most inaccurate.
Summary of the invention
It is an object of the invention to provide measuring method and the device of the capacitance of a kind of differential capacitance, solve existing skill
The problem that the capacitance of the differential capacitance between CAN height bit line and CAN low-bit line cannot be measured in art.
In order to achieve the above object, the embodiment of the present invention provides the differential electrical between a kind of CAN height bit line and CAN low-bit line
The measuring method of the capacitance held, the direct-to-ground capacitance of CAN height bit line is equal with the direct-to-ground capacitance of CAN low-bit line, described measurement side
Method includes:
Obtain the first capacitance of the direct-to-ground capacitance of CAN height bit line or the first electric capacity of the direct-to-ground capacitance of CAN low-bit line
Value；
Obtain the capacitance sum of described first capacitance and the second capacitance of differential capacitance；
According to described first capacitance and described capacitance sum, determine the second capacitance of differential capacitance.
Wherein, the direct-to-ground capacitance of described CAN height bit line, the direct-to-ground capacitance of described CAN low-bit line and described CAN height bit line
With the differential capacitance between CAN low-bit line constitutes circuit under test.
Wherein, the first capacitance of the direct-to-ground capacitance of CAN height bit line or the first of the direct-to-ground capacitance of CAN low-bit line is obtained
The step of capacitance, including:
Utilize the first measuring circuit that described circuit under test is measured, determine CAN height bit line direct-to-ground capacitance first
First capacitance of the direct-to-ground capacitance of capacitance or CAN low-bit line.
Wherein, obtain the step of described first capacitance and the capacitance sum of the second capacitance of differential capacitance, including:
Utilize the second measuring circuit that described circuit under test is measured, determine described first capacitance and differential capacitance
The capacitance sum of the second capacitance.
Wherein, described first measuring circuit includes: for produce predetermined amplitude square-wave signal the first signal generator,
Waveform the first oscillograph, the first resistance and first diode of waveform or CAN low-bit line for gathering CAN height bit line；
Wherein,
By a wire short circuit between described CAN height bit line and described CAN low-bit line, described CAN height bit line respectively with institute
The one end stating first oscillographic one end and described first resistance connects, described first oscillographic other end ground connection, and described the
The other end of one resistance is connected with the negative pole of described first diode, and the positive pole of described first diode is sent out with described first signal
One end of raw device connects, the other end ground connection of described first signal generator.
Wherein, described second measuring circuit includes: for produce predetermined amplitude square-wave signal secondary signal generator,
Waveform the second oscillograph, the second resistance and second diode of waveform or CAN low-bit line for gathering CAN height bit line；
Wherein,
Described CAN low-bit line is shorted to ground by a wire, and described CAN height bit line is respectively with described second oscillographic one
End and described second resistance one end connect, described second oscillographic other end ground connection, the other end of described second resistance with
The negative pole of described second diode connects, and the positive pole of described second diode is connected with one end of described secondary signal generator,
The other end ground connection of described secondary signal generator.
The embodiment of the present invention also provides for the survey of the capacitance of the differential capacitance between a kind of CAN height bit line and CAN low-bit line
Amount device, the direct-to-ground capacitance of CAN height bit line is equal with the direct-to-ground capacitance of CAN low-bit line, and described measurement apparatus includes:
First acquisition module, for obtaining the first capacitance of the direct-to-ground capacitance of CAN height bit line or the right of CAN low-bit line
First capacitance of ground electric capacity；
Second acquisition module, for obtain the second capacitance of described first capacitance and differential capacitance capacitance it
With；
Determine module, for according to described first capacitance and described capacitance sum, determining the second electricity of differential capacitance
Capacitance.
Wherein, the direct-to-ground capacitance of described CAN height bit line, the direct-to-ground capacitance of described CAN low-bit line and described CAN height bit line
With the differential capacitance between CAN low-bit line constitutes circuit under test.
Wherein, described first acquisition module includes:
First obtains submodule, is used for utilizing the first measuring circuit to measure described circuit under test, determines that CAN is high-order
First capacitance of the direct-to-ground capacitance of line or the first capacitance of the direct-to-ground capacitance of CAN low-bit line.
Wherein, described second acquisition module includes:
Second obtains submodule, is used for utilizing the second measuring circuit to measure described circuit under test, determines described the
The capacitance sum of the second capacitance of one capacitance and differential capacitance.
Wherein, described first measuring circuit includes: for produce predetermined amplitude square-wave signal the first signal generator,
Waveform the first oscillograph, the first resistance and first diode of waveform or CAN low-bit line for gathering CAN height bit line；
Wherein,
By a wire short circuit between described CAN height bit line and described CAN low-bit line, described CAN height bit line respectively with institute
The one end stating first oscillographic one end and described first resistance connects, described first oscillographic other end ground connection, and described the
The other end of one resistance is connected with the negative pole of described first diode, and the positive pole of described first diode is sent out with described first signal
One end of raw device connects, the other end ground connection of described first signal generator.
Wherein, described second measuring circuit includes: for produce predetermined amplitude square-wave signal secondary signal generator,
Waveform the second oscillograph, the second resistance and second diode of waveform or CAN low-bit line for gathering CAN height bit line；
Wherein,
Described CAN low-bit line is shorted to ground by a wire, and described CAN height bit line is respectively with described second oscillographic one
End and described second resistance one end connect, described second oscillographic other end ground connection, the other end of described second resistance with
The negative pole of described second diode connects, and the positive pole of described second diode is connected with one end of described secondary signal generator,
The other end ground connection of described secondary signal generator.
The technique scheme of the present invention at least has the advantages that
In the measuring method of the capacitance of the differential capacitance of the embodiment of the present invention and device, use test step by step method, first
First test the first capacitance of the direct-to-ground capacitance of CAN height bit line or the first capacitance of the direct-to-ground capacitance of CAN low-bit line, then survey
Direct-to-ground capacitance and the differential capacitance of examination CAN height bit line and, finally by the capacitance that can be calculated differential capacitance；This measurement
Method is capable of the measurement to differential capacitance and degree of accuracy is higher.
Accompanying drawing explanation
Fig. 1 represents the capacitance of the differential capacitance between CAN height bit line and the CAN low-bit line that the embodiment of the present invention provides
The basic step flow chart of measuring method；
Fig. 2 represents the capacitance of the differential capacitance between CAN height bit line and the CAN low-bit line that the embodiment of the present invention provides
The circuit diagram of the first measuring circuit in measuring method；
Fig. 3 represents the capacitance of the differential capacitance between CAN height bit line and the CAN low-bit line that the embodiment of the present invention provides
The circuit diagram of the second measuring circuit in measuring method；
Fig. 4 represents the capacitance of the differential capacitance between CAN height bit line and the CAN low-bit line that the embodiment of the present invention provides
The oscillogram that in measuring method, oscillograph catches；
Fig. 5 represents the structure chart of the measurement apparatus of the capacitance of the differential capacitance between CAN height bit line and CAN low-bit line.
Detailed description of the invention
For making the technical problem to be solved in the present invention, technical scheme and advantage clearer, below in conjunction with accompanying drawing and tool
Body embodiment is described in detail.
As it is shown in figure 1, the capacitance of the differential capacitance between the embodiment of the present invention a kind of CAN height bit line and CAN low-bit line
Measuring method, the direct-to-ground capacitance of CAN height bit line is equal with the direct-to-ground capacitance of CAN low-bit line, and described measuring method includes:
Step 11, obtains the of first capacitance of direct-to-ground capacitance of CAN height bit line or the direct-to-ground capacitance of CAN low-bit line
One capacitance；
Step 12, obtains the capacitance sum of described first capacitance and the second capacitance of differential capacitance；
Step 13, according to described first capacitance and described capacitance sum, determines the second capacitance of differential capacitance.
The above embodiment of the present invention needs direct-to-ground capacitance and the direct-to-ground capacitance of CAN low-bit line first to CAN height bit line
Measure, the direct-to-ground capacitance of measured direct-to-ground capacitance and the CAN low-bit line understanding CAN height bit line closely, the present invention
The direct-to-ground capacitance giving tacit consent to CAN height bit line in embodiment is equal with the direct-to-ground capacitance of CAN low-bit line, is set to Cin。
The method using test step by step in the embodiment of the present invention measures the capacitance of differential capacitance.Concrete, such as Fig. 2 and figure
Shown in 3, the direct-to-ground capacitance C of described CAN height bit linein, the direct-to-ground capacitance C of described CAN low-bit lineinAnd described CAN height bit line and
Differential capacitance C between CAN low-bit linediffConstitute circuit under test DUT.
Further, step 11 includes:
Step 111, utilizes the first measuring circuit to measure described circuit under test, determines the electricity over the ground of CAN height bit line
The first capacitance held or the first capacitance of the direct-to-ground capacitance of CAN low-bit line.
And as in figure 2 it is shown, described first measuring circuit includes: for producing the first signal of the square-wave signal of predetermined amplitude
Generator, for gathering waveform or waveform first oscillograph of CAN low-bit line, the first resistance R of CAN height bit lineTestAnd
First diode D1；Wherein,
By a wire short circuit between described CAN height bit line and described CAN low-bit line, described CAN height bit line respectively with institute
State first oscillographic one end and described first resistance RTestOne end connect, described first oscillographic other end ground connection, institute
State the first resistance RTestThe other end be connected with the negative pole of described first diode D1, the positive pole of described first diode D1 and institute
The one end stating the first signal generator connects, the other end ground connection of described first signal generator.
In the above embodiment of the present invention, the first oscillograph has CAN/LIN decoding function；And this first oscillograph support
The input of CAN_H (CAN height bit line)/CAN_L (CAN low-bit line) single channel or CAN_H (CAN height bit line)/CAN_L (CAN low level
Line) use difference detector Differential Input.
It is also preferred that the left utilize the first measuring circuit that described circuit under test measures the concrete steps determining the first capacitance
For:
Step 21, sending amplitude with the first signal generator to the CAN port of circuit under test DUT is the square-wave signal of 5v；
Step 22, monitors waveform or the waveform of CAN_L of CAN_H with the first oscillograph, the i.e. first signal generator
Outfan；When the first signal generator stops square-wave signal transmission, catch waveform or the CAN_ of CAN_H with the first oscillograph
The waveform of L, as shown in Figure 4；
Step 23, as shown in Figure 4, adjusts X1, the cursor of X2, Y1, Y2, navigates to VcanAnd 0.37VcanPosition, from showing
Obtaining Δ X and Δ Y in ripple device, wherein Δ X is exactly discharge time constant τ of DUT internal capacitance, calculates capacitance according to formula
Cin, due in the first measuring circuit shown in Fig. 2 CAN_H and CAN_L line short circuit, so the total capacitance in circuit is Cin's
Twice, then:
It should be noted that the first resistance RTestOccurrence according to whether circuit under test DUT comprises terminal resistance phase
Close, such as when DUT comprises terminal resistance, the first resistance RTest=120 Ω；When DUT does not comprises terminal resistance, first
Resistance RTest=60 Ω.
Need further exist for explanation, the amplitude of square-wave signal of the first signal generator transmission, the resistance of the first resistance
The size of the magnitude of voltage used in the acquisition process of value and discharge time constant τ is presently preferred embodiments of the present invention, need not
In the protection domain limiting the application.
Further, step 12 includes:
Step 121, utilizes the second measuring circuit to measure described circuit under test, determines described first capacitance and difference
Divide the capacitance sum of the second capacitance of electric capacity.
And as it is shown on figure 3, described second measuring circuit includes: for producing the secondary signal of the square-wave signal of predetermined amplitude
Generator, for gathering waveform or waveform second oscillograph of CAN low-bit line, the second resistance R of CAN height bit lineTestAnd
Second diode D2；Wherein,
Described CAN low-bit line is shorted to ground by a wire, and described CAN height bit line is respectively with described second oscillographic one
End and described second resistance RTestOne end connect, described second oscillographic other end ground connection, described second resistance RTestAnother
One end is connected with the negative pole of described second diode D2, the positive pole of described second diode D2 and described secondary signal generator
One end connects, the other end ground connection of described secondary signal generator.
In the above embodiment of the present invention, the second oscillograph has CAN/LIN decoding function；And this second oscillograph support
The input of CAN_H (CAN height bit line)/CAN_L (CAN low-bit line) single channel or CAN_H (CAN height bit line)/CAN_L (CAN low level
Line) use difference detector Differential Input.
It is also preferred that the left utilize the second measuring circuit that described circuit under test is measured determine the first capacitance and differential capacitance
The concretely comprising the following steps of capacitance sum of the second capacitance:
Step 31, sending amplitude with secondary signal generator to the CAN port of circuit under test DUT is the square-wave signal of 5V；
Step 32, utilizes waveform or the waveform of CAN_L, i.e. secondary signal generator of the second oscillograph monitoring CAN_H
Outfan；When secondary signal generator stop square-wave signal send time, with second oscillograph seizure CAN_H waveform or
The waveform of CAN_L, as shown in Figure 4；
Step 33, as shown in Figure 4, adjusts X1, the cursor of X2, Y1, Y2, navigates to VcanAnd 0.37VcanPosition, and can
Directly directly to obtain Δ X and Δ Y from oscillograph, wherein Δ X is exactly discharge time constant τ of DUT internal capacitance, due to figure
The second measuring circuit shown in 3 is shorted to ground CAN_L, so the direct-to-ground capacitance C that the electric capacity calculated is CAN_HinWith difference
Divide electric capacity CdiffSum, it may be assumed that
It should be noted that the second resistance RTestOccurrence according to whether circuit under test DUT comprises terminal resistance phase
Close, such as when DUT comprises terminal resistance, the second resistance RTest=120 Ω；When DUT does not comprises terminal resistance, second
Resistance RTest=60 Ω.
Need further exist for explanation, the amplitude of square-wave signal of secondary signal generator transmission, the resistance of the second resistance
The size of the magnitude of voltage used in the acquisition process of value and discharge time constant τ is presently preferred embodiments of the present invention, need not
In the protection domain limiting the application.
Concrete, differential capacitance C can be obtained according to formula (1) and formula (2)diffCapacitance, it may be assumed that
Therefore differential capacitance C can be obtained according to formula (3)diffCapacitance.
It should be noted that the same section of above-mentioned first measuring circuit and the second measuring circuit can use identical hard
Part equipment, it would however also be possible to employ different hardware devices, is not especially limited at this.
To sum up, the above embodiment of the present invention uses test step by step method, first tests the direct-to-ground capacitance of CAN height bit line
The first capacitance or first capacitance of direct-to-ground capacitance of CAN low-bit line, the direct-to-ground capacitance of re-test CAN height bit line and difference
Divide the sum of electric capacity, finally by the capacitance that can be calculated differential capacitance；This measuring method is capable of differential capacitance
Measure and degree of accuracy is higher.
In order to preferably realize above-mentioned purpose, as it is shown in figure 5, another embodiment of the present invention also provides for an a kind of CAN high position
The measurement apparatus of the capacitance of the differential capacitance between line and CAN low-bit line, the direct-to-ground capacitance of CAN height bit line and CAN low-bit line
Direct-to-ground capacitance equal, described measurement apparatus includes:
First acquisition module 51, for obtaining first capacitance of direct-to-ground capacitance of CAN height bit line or CAN low-bit line
First capacitance of direct-to-ground capacitance；
Second acquisition module 52, for obtain the second capacitance of described first capacitance and differential capacitance capacitance it
With；
Determine module 53, for according to described first capacitance and described capacitance sum, determine the second of differential capacitance
Capacitance.
Concrete, the direct-to-ground capacitance of the bit line of CAN height described in the above embodiment of the present invention, described CAN low-bit line right
Differential capacitance between ground electric capacity and described CAN height bit line and CAN low-bit line constitutes circuit under test.
Concrete, described in the above embodiment of the present invention, the first acquisition module includes:
First obtains submodule, is used for utilizing the first measuring circuit to measure described circuit under test, determines that CAN is high-order
First capacitance of the direct-to-ground capacitance of line or the first capacitance of the direct-to-ground capacitance of CAN low-bit line.
Concrete, described in the above embodiment of the present invention, the second acquisition module includes:
Second obtains submodule, is used for utilizing the second measuring circuit to measure described circuit under test, determines described the
The capacitance sum of the second capacitance of one capacitance and differential capacitance.
Concrete, described in the above embodiment of the present invention, the first measuring circuit includes: for producing the side of predetermined amplitude
First signal generator of ripple signal, for gather the waveform of CAN height bit line or waveform first oscillograph of CAN low-bit line,
First resistance and the first diode；Wherein,
By a wire short circuit between described CAN height bit line and described CAN low-bit line, described CAN height bit line respectively with institute
The one end stating first oscillographic one end and described first resistance connects, described first oscillographic other end ground connection, and described the
The other end of one resistance is connected with the negative pole of described first diode, and the positive pole of described first diode is sent out with described first signal
One end of raw device connects, the other end ground connection of described first signal generator.
Concrete, described in the above embodiment of the present invention, the second measuring circuit includes: for producing the side of predetermined amplitude
The secondary signal generator of ripple signal, for gather the waveform of CAN height bit line or waveform second oscillograph of CAN low-bit line,
Second resistance and the second diode；Wherein,
Described CAN low-bit line is shorted to ground by a wire, and described CAN height bit line is respectively with described second oscillographic one
End and described second resistance one end connect, described second oscillographic other end ground connection, the other end of described second resistance with
The negative pole of described second diode connects, and the positive pole of described second diode is connected with one end of described secondary signal generator,
The other end ground connection of described secondary signal generator.
It should be noted that use test step by step method in embodiments of the invention, first test CAN height bit line is over the ground
First capacitance of electric capacity or the first capacitance of the direct-to-ground capacitance of CAN low-bit line, the direct-to-ground capacitance of re-test CAN height bit line
With differential capacitance and, finally by the capacitance that can be calculated differential capacitance；This measuring method is capable of differential electrical
Measurement and the degree of accuracy held are higher.
It should be noted that the electricity of the differential capacitance between CAN height bit line and the CAN low-bit line of embodiment of the present invention offer
The measurement apparatus of capacitance is the measuring method of the capacitance applying the differential capacitance between above-mentioned CAN height bit line and CAN low-bit line
Measurement apparatus, all realities of the measuring method of the capacitance of the differential capacitance between the most above-mentioned CAN height bit line and CAN low-bit line
Execute example and be all applicable to this measurement apparatus, and all can reach same or analogous beneficial effect.
The above is the preferred embodiment of the present invention, it is noted that for those skilled in the art
For, on the premise of without departing from principle of the present invention, it is also possible to make some improvements and modifications, these improvements and modifications are also
Should be regarded as protection scope of the present invention.
Claims (12)
1. the measuring method of the capacitance of the differential capacitance between a CAN height bit line and CAN low-bit line, it is characterised in that CAN
The direct-to-ground capacitance of high bit line is equal with the direct-to-ground capacitance of CAN low-bit line, and described measuring method includes:
Obtain the first capacitance of the direct-to-ground capacitance of CAN height bit line or the first capacitance of the direct-to-ground capacitance of CAN low-bit line；
Obtain the capacitance sum of described first capacitance and the second capacitance of differential capacitance；
According to described first capacitance and described capacitance sum, determine the second capacitance of differential capacitance.
Measuring method the most according to claim 1, it is characterised in that the direct-to-ground capacitance of described CAN height bit line, described CAN
Differential capacitance between direct-to-ground capacitance and described CAN height bit line and the CAN low-bit line of low-bit line constitutes circuit under test.
Measuring method the most according to claim 2, it is characterised in that obtain the first electricity of the direct-to-ground capacitance of CAN height bit line
The step of the first capacitance of the direct-to-ground capacitance of capacitance or CAN low-bit line, including:
Utilize the first measuring circuit that described circuit under test is measured, determine the first electric capacity of the direct-to-ground capacitance of CAN height bit line
First capacitance of the direct-to-ground capacitance of value or CAN low-bit line.
Measuring method the most according to claim 2, it is characterised in that obtain the of described first capacitance and differential capacitance
The step of the capacitance sum of two capacitances, including:
Utilize the second measuring circuit that described circuit under test is measured, determine the second of described first capacitance and differential capacitance
The capacitance sum of capacitance.
Measuring method the most according to claim 3, it is characterised in that described first measuring circuit includes: be used for producing pre-
If the first signal generator of the square-wave signal of amplitude, for gathering the waveform the of the waveform of CAN height bit line or CAN low-bit line
One oscillograph, the first resistance and the first diode；Wherein,
By a wire short circuit between described CAN height bit line and described CAN low-bit line, described CAN height bit line is respectively with described the
One end of one oscillographic one end and described first resistance connects, described first oscillographic other end ground connection, described first electricity
The other end of resistance is connected with the negative pole of described first diode, the positive pole of described first diode and described first signal generator
One end connect, the other end ground connection of described first signal generator.
Measuring method the most according to claim 4, it is characterised in that described second measuring circuit includes: be used for producing pre-
If the secondary signal generator of the square-wave signal of amplitude, for gathering the waveform the of the waveform of CAN height bit line or CAN low-bit line
Two oscillographs, the second resistance and the second diode；Wherein,
Described CAN low-bit line by a wire be shorted to ground, described CAN height bit line respectively with described second oscillographic one end and
One end of described second resistance connects, and described second oscillographic other end ground connection, the other end of described second resistance is with described
The negative pole of the second diode connects, and the positive pole of described second diode is connected with one end of described secondary signal generator, described
The other end ground connection of secondary signal generator.
7. the measurement apparatus of the capacitance of the differential capacitance between a CAN height bit line and CAN low-bit line, it is characterised in that CAN
The direct-to-ground capacitance of high bit line is equal with the direct-to-ground capacitance of CAN low-bit line, and described measurement apparatus includes:
First acquisition module, the electricity over the ground of the first capacitance or CAN low-bit line for obtaining the direct-to-ground capacitance of CAN height bit line
The first capacitance held；
Second acquisition module, for obtaining the capacitance sum of described first capacitance and the second capacitance of differential capacitance；
Determine module, for according to described first capacitance and described capacitance sum, determine the second capacitance of differential capacitance.
Measurement apparatus the most according to claim 7, it is characterised in that the direct-to-ground capacitance of described CAN height bit line, described CAN
Differential capacitance between direct-to-ground capacitance and described CAN height bit line and the CAN low-bit line of low-bit line constitutes circuit under test.
Measurement apparatus the most according to claim 8, it is characterised in that described first acquisition module includes:
First obtains submodule, is used for utilizing the first measuring circuit to measure described circuit under test, determines CAN height bit line
First capacitance of direct-to-ground capacitance or the first capacitance of the direct-to-ground capacitance of CAN low-bit line.
Measurement apparatus the most according to claim 8, it is characterised in that described second acquisition module includes:
Second obtains submodule, is used for utilizing the second measuring circuit to measure described circuit under test, determines described first electricity
The capacitance sum of the second capacitance of capacitance and differential capacitance.
11. measurement apparatus according to claim 9, it is characterised in that described first measuring circuit includes: be used for producing pre-
If the first signal generator of the square-wave signal of amplitude, for gathering the waveform the of the waveform of CAN height bit line or CAN low-bit line
One oscillograph, the first resistance and the first diode；Wherein,
By a wire short circuit between described CAN height bit line and described CAN low-bit line, described CAN height bit line is respectively with described the
One end of one oscillographic one end and described first resistance connects, described first oscillographic other end ground connection, described first electricity
The other end of resistance is connected with the negative pole of described first diode, the positive pole of described first diode and described first signal generator
One end connect, the other end ground connection of described first signal generator.
12. measurement apparatus according to claim 10, it is characterised in that described second measuring circuit includes: be used for producing
The secondary signal generator of the square-wave signal of predetermined amplitude, for gathering waveform or the waveform of CAN low-bit line of CAN height bit line
Second oscillograph, the second resistance and the second diode；Wherein,
Described CAN low-bit line by a wire be shorted to ground, described CAN height bit line respectively with described second oscillographic one end and
One end of described second resistance connects, and described second oscillographic other end ground connection, the other end of described second resistance is with described
The negative pole of the second diode connects, and the positive pole of described second diode is connected with one end of described secondary signal generator, described
The other end ground connection of secondary signal generator.
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| CN110912763A (en) * | 2018-09-17 | 2020-03-24 | 联合汽车电子有限公司 | CAN bus test integrated circuit, test system and test method |
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