CN211086468U - L CR tester - Google Patents
L CR tester Download PDFInfo
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- CN211086468U CN211086468U CN201921647007.7U CN201921647007U CN211086468U CN 211086468 U CN211086468 U CN 211086468U CN 201921647007 U CN201921647007 U CN 201921647007U CN 211086468 U CN211086468 U CN 211086468U
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- frequency synthesizer
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Abstract
The utility model belongs to the technical field of the L CR test technique and specifically relates to a L CR tester, frequency sweep signal generator includes controller, digital frequency synthesizer and voltage gain control circuit, digital frequency synthesizer synthesizes the frequency that becomes needs under the control of controller and passes through voltage gain control circuit output, wherein, digital frequency synthesizer adopts AD9851, the controller adopts AT89C51 control digital frequency synthesizer to produce the required waveform that the frequency can continuous variation, the controller adopts parallel connection structure with digital frequency synthesizer, digital frequency synthesizer has 40 bit control words, wherein contain 32 bit frequency control words, choose 30MHz as AD 9851's reference clock.
Description
Technical Field
The utility model discloses L CR tests technical field, concretely relates to L CR tester.
Background
The existing L CR tester has single frequency point, so that only single measurement of parameters such as an inductor L, a capacitor C, a resistor R, a quality factor Q, a loss tangent value D and the like can be realized, the exact influence of input frequency on a system impedance value cannot be well reflected, and the problems of complex hardware circuit, difficult debugging and low reliability also exist.
SUMMERY OF THE UTILITY MODEL
The utility model discloses the technical problem that will solve lies in L CR tester, and the hardware circuit who solves current tester existence is complicated, problem that the reliability is low.
An L CR tester comprises a sweep frequency signal generator, wherein the sweep frequency signal generator comprises a controller, a digital frequency synthesizer and a voltage gain control circuit, the digital frequency synthesizer synthesizes required frequency under the control of the controller and then outputs the frequency through the voltage gain control circuit, the digital frequency synthesizer adopts AD9851, the controller adopts AT89C51 to control the digital frequency synthesizer to generate required waveform with continuously variable frequency, the controller and the digital frequency synthesizer adopt a parallel connection structure, the digital frequency synthesizer is provided with 40-bit control words, the digital frequency synthesizer comprises 32-bit frequency control words, and 30MHz is selected as a reference clock of the AD 9851.
Furthermore, the frequency of the sweep frequency signal generator is changed to 0-50MHz, and a low-pass filter is connected in series with an IOUT port of the sweep frequency signal generator to filter out high frequency and harmonic waves.
Further, the low-pass filter is an elliptical low-pass filter.
Furthermore, the voltage gain control circuit is an ultra-low noise and precisely controlled variable gain amplifier with the model number of AD603, the maximum gain error is 0.5dB, and the gain range is-1.07 dB to +41.07 dB.
Furthermore, the sweep frequency output is detected by a detection circuit, converted by an A/D converter and then received by a receiver and uploaded to an upper computer.
Furthermore, the detection circuit comprises an amplifier, the non-inverting input end of the amplifier is connected with the impedance to be detected which is connected with the scanning output, a standard resistor is connected between the non-inverting input end and the output end, and the inverting input end of the amplifier is grounded.
The utility model and the prior art beneficial effect lie in: the novel circuit has the advantages of simple structure, capability of generating frequency sweep signals with linearly changed frequency, equal amplitude of output of the frequency sweep signals, simple circuit structure, large frequency sweep width, good linearity of the frequency sweep signals, capability of generating frequency marks synchronous with the frequency sweep signals and constant output impedance.
Drawings
Fig. 1 is a block diagram of the structure of the frequency sweep signal generator of the present invention;
FIG. 2 is an overall block diagram of the present invention;
fig. 3 is a circuit diagram of a voltage gain control circuit according to the present invention;
fig. 4 is an elliptical low-pass filter circuit diagram provided by the present invention;
FIG. 5 is a circuit diagram of a digital frequency synthesizer according to the present invention
Fig. 6 is a circuit diagram of the detection circuit.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Examples
Referring to fig. 1 and fig. 2, an L CR tester comprises a sweep frequency signal generator, wherein the sweep frequency signal generator comprises a controller, a digital frequency synthesizer and a voltage gain control circuit, the digital frequency synthesizer synthesizes required frequency under the control of the controller and outputs the frequency through the voltage gain control circuit, the digital frequency synthesizer adopts AD9851, the controller adopts AT89C51 to control the digital frequency synthesizer to generate required waveform with continuously variable frequency, the controller and the digital frequency synthesizer adopt a parallel connection structure, and the digital frequency synthesizer adopts a parallel connection structureThe rate synthesizer has 40-bit control words, including 32-bit frequency control words, 30MHz is selected as the reference clock of AD9851, the system clock frequency can reach 180MHz when the multiplier works, when K is 1, the resolution can reach 0.04Hz, according to Nyquist sampling theorem, when K is maximum (232-1), the maximum output frequency is fref/2。
Referring to fig. 5, a port R of a digital frequency synthesizerSETConnecting regulating resistor R2The novel characteristic is realized by changing the resistance R2The resistance value can regulate the output current, and the port IOUT is 39.93/R2In general R2Take 3.9K Ω, IOUT outputs 10 mA. Through the output terminal R4And an output end R5The output current is converted to a voltage.
The digital frequency synthesizer and the voltage gain control circuit form a sweep frequency signal generator, the frequency change is 0-50MHz, and an elliptical low-pass filter is connected in series with an IOUT port of the digital frequency synthesizer to allow for high frequency and harmonic waves. Referring to fig. 4, the elliptic low-pass filter can achieve the best approximation of an ideal low-pass compared with other all-pole filters, and the technical index achieved is the highest under the condition of the same order, so the elliptic low-pass filter is selected.
Referring to fig. 3, the voltage gain control circuit is an ultra-low noise, precisely controlled variable gain amplifier of model AD603, with a maximum gain error of 0.5dB and a gain range of-1.07 dB to +41.07 dB. The gain (dB) is linear with the control voltage. Therefore, the gain of the amplifier can be controlled by controlling the voltage, so that the output amplitude of the signal generator is more stable.
The output of the voltage gain control circuit is detected by a detection circuit, and the detection circuit is converted by an A/D converter and received by a receiver and output to an upper computer
The sweep frequency signal is preferably 50Hz, so that the A/D rate is greater than 50Hz., and the optimal A/D converter of sigma- △ type, the speed and the accuracy meet the requirements shown in Table 1.
Table 1:
the sweep output is detected by a detection circuit, connected to the sweep output, detected by a detection circuit, converted by an A/D converter, received by a receiver and uploaded to an upper computer.
Referring to fig. 6, the detection circuit includes an amplifier, the non-inverting input terminal of the amplifier is connected to the impedance Zx to be detected connected to the scan output, a standard resistor Rs is connected between the non-inverting input terminal and the output terminal, and the inverting input terminal of the amplifier is grounded.
The upper computer obtains impedance values under different frequencies according to the measured data, and draws an impedance characteristic curve, so that the influence of the frequency on the element and the system can be observed.
The above description is only exemplary of the present invention and should not be taken as limiting the scope of the present invention, as any modifications, equivalents, improvements and the like made within the spirit and principles of the present invention are intended to be included within the scope of the present invention.
Claims (6)
1. An L CR tester is characterized in that the tester comprises a sweep signal generator, the sweep signal generator comprises a controller, a digital frequency synthesizer and a voltage gain control circuit, the digital frequency synthesizer is synthesized into required frequency under the control of the controller and then is output through the voltage gain control circuit, wherein the digital frequency synthesizer adopts AD9851, the controller adopts AT89C51 to control the digital frequency synthesizer to generate required waveforms with continuously variable frequency, the controller and the digital frequency synthesizer adopt a parallel connection structure, the digital frequency synthesizer is provided with 40-bit control words, the digital frequency synthesizer comprises 32-bit frequency control words, and 30MHz is selected as a reference clock of the AD 9851.
2. An L CR tester as claimed in claim 1 wherein the frequency of the swept frequency signal generator is varied from 0 to 50MHz, and a low pass filter is connected in series with the IOUT port of the swept frequency signal generator to filter out high frequencies and harmonics.
3. An L CR tester as claimed in claim 2 wherein the low pass filter is an elliptical low pass filter.
4. A L CR tester as claimed in claim 1, wherein the voltage gain control circuit is an ultra low noise, precision controlled variable gain amplifier of type AD603 with a maximum gain error of 0.5dB and a gain range of-1.07 dB to +41.07 dB.
5. A L CR tester as claimed in claim 1, wherein the swept frequency output is detected by a detection circuit, converted by an a/D converter and received by a receiver and uploaded to an upper computer.
6. An L CR tester as claimed in claim 5 wherein the detection circuit includes an amplifier having a non-inverting input connected to the impedance to be tested connected to the scan output, a reference resistor connected between the non-inverting input and the output, and an inverting input connected to ground.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201921647007.7U CN211086468U (en) | 2019-09-29 | 2019-09-29 | L CR tester |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201921647007.7U CN211086468U (en) | 2019-09-29 | 2019-09-29 | L CR tester |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN211086468U true CN211086468U (en) | 2020-07-24 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN201921647007.7U Active CN211086468U (en) | 2019-09-29 | 2019-09-29 | L CR tester |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114089040A (en) * | 2021-11-01 | 2022-02-25 | 苏州茂鼎电子科技有限公司 | Multichannel high-precision LCR test system |
| CN115201570A (en) * | 2022-09-09 | 2022-10-18 | 青岛积成电子股份有限公司 | Impedance testing system based on LCR digital bridge and Smith circular diagram |
-
2019
- 2019-09-29 CN CN201921647007.7U patent/CN211086468U/en active Active
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114089040A (en) * | 2021-11-01 | 2022-02-25 | 苏州茂鼎电子科技有限公司 | Multichannel high-precision LCR test system |
| CN115201570A (en) * | 2022-09-09 | 2022-10-18 | 青岛积成电子股份有限公司 | Impedance testing system based on LCR digital bridge and Smith circular diagram |
| CN115201570B (en) * | 2022-09-09 | 2023-01-03 | 青岛积成电子股份有限公司 | Impedance testing system based on LCR digital bridge and Smith circular diagram |
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