CN201724993U - Radiation noise testing system for digital gravity metering device - Google Patents

Abstract

The utility model relates to a radiation noise testing system for a digital gravity metering device, which comprises a singlechip digital gravity metering device, a high-frequency current clamp, a noise separating network, a spectrum analyzer and a computer, wherein the one measuring ring of the high-frequency current clamp is arranged on a live line of a power line of the digital gravity metering device and a ground wire, and the other measuring ring of the high-frequency current clamp is arranged on a center line of the power line of the digital gravity metering device and the ground wire; the noise separating network is used for separating overall noise information measured by the high-frequency current clamp into differential mode transmitting noise information and common mode transmitting noise information; the spectrum analyzer is connected with an output end of the noise separating network; and the computer is connected with the spectrum analyzer. The utility model is firstly used for measuring the common-mode noise current of the singlechip digital gravity metering device by the high-frequency current clamp and the noise separating network, and then estimating the radiation noise in advance by the computer according to the common-mode noise current.

Description

A kind of radiated noise test macro that is used for digital gravimetric equipment

Technical field

The utility model relates to a kind of radiated noise test macro that is used for digital gravimetric equipment, belongs to electromagnetic compatibility test and power line communication field.

Background technology

Electronic equipment must be tested by corresponding standard before carrying out marketing, and wherein one is exactly the test of electromagnetic radiation interference standard.And mainly cause owing to its transmission cable radiation based on the radiated noise of the digital gravimetric equipment of single-chip microcomputer.And the existing cost that adopts microwave dark room to measure electromagnetic radiation is higher, therefore how at the characteristics of the digital gravimetric equipment of single-chip microcomputer, developing a kind of radiation noise test method short-cut method that is used for digital gravimetric equipment is the problem that the present invention studies.

Summary of the invention

The utility model purpose provides a kind of radiated noise test macro that is used for digital gravimetric equipment, this system is measured the common mode noise current of the digital gravimetric equipment of single-chip microcomputer earlier by high-frequency current clamp and noise separating network, estimates radiated noise by computing machine according to common mode noise current again.

For achieving the above object, the technical solution adopted in the utility model is: a kind of radiated noise test macro that is used for digital gravimetric equipment,

Comprise: the digital gravimetric equipment of single-chip microcomputer;

High-frequency current clamp, a measurement ring in the high-frequency current clamp places on the live wire and ground wire of digital gravimetric device power supply (DPS) line, to extract in the digital gravimetric equipment in the power lead live wire overall noise information of line over the ground; Another measurement ring in the high-frequency current clamp is placed on the center line and ground wire of digital gravimetric device power supply (DPS) line, to extract in the digital gravimetric equipment in the power lead center line the overall noise information of ground wire;

Noise separating network, the input end of this noise separating network is connected with described high-frequency current clamp output terminal, and being used for high-frequency current clamp is measured the overall noise information separated is differential mode conducted noise information and common mode conducted noise information;

Spectrum analyzer, the output terminal of this spectrum analyzer noise separating network connects, be used for described differential mode conducted noise information and common mode conducted noise information are carried out computing in conjunction with the transfer impedance of described high-frequency current clamp, obtain differential mode conducted noise electric current and common mode conducted noise electric current.

Computing machine, this computing machine is connected with spectrum analyzer, is used for drawing radiated noise according to common mode conducted noise electric current by software.

Because the technique scheme utilization, the utility model compared with prior art has following advantage:

1, the utility model to be measuring the conducted noise in the digital gravimetric equipment of single-chip microcomputer, and it is separated into common-mode noise and differential mode noise, and adopts corresponding squelch measure to make electric line communication system reach standard-required at conduction portion.

2, the utility model is estimated for radiated noise according to common mode current, can save great number measurement expense such as utilizing microwave dark room.

3, the utility model adopts separated network to extract common-mode noise, and designs corresponding wave filter and suppress for its common-mode noise, thereby reaches the purpose that suppresses the digital gravimetric radiation of equipment of single-chip microcomputer noise.Make more effective to the radiation EMI Noise Suppression.

4, the utility model uses high-frequency current clamp can measure little electric current to the microampere magnitude.

5, the utility model measure lead between balance to guarantee to optimize the integrality of signal.

Description of drawings

The measurement system diagram that Fig. 1 high-frequency current clamp and noise separating network are formed;

Fig. 2 high-frequency current clamp circuit topological structure figure;

Fig. 3 radio-frequency current probe is estimated principle wherein, and I1,12...In are every segment corresponding current, and E1, E2...En are the electric field of every section electric current correspondence;

Fig. 4 amplifies the position for causing the radiated noise reason based on the digital gravimetric circuitry of single-chip microcomputer figure;

Fig. 5 high-frequency current clamp transfer impedance test pattern;

Fig. 6 noise separating network high frequency characteristics figure;

Fig. 7 radiated noise estimation results.

Embodiment

Below in conjunction with drawings and Examples the utility model is further described:

Embodiment: a kind of radiated noise test macro that is used for digital gravimetric equipment shown in accompanying drawing 1-4, comprising:

The digital gravimetric equipment of single-chip microcomputer;

High-frequency current clamp, a measurement ring in the high-frequency current clamp places on the live wire and ground wire of digital gravimetric device power supply (DPS) line, to extract in the digital gravimetric equipment in the power lead live wire overall noise information of line over the ground; Another measurement ring in the high-frequency current clamp is placed on the center line and ground wire of digital gravimetric device power supply (DPS) line, to extract in the digital gravimetric equipment in the power lead center line the overall noise information of ground wire;

Noise separating network, the input end of this noise separating network is connected with described high-frequency current clamp output terminal, and being used for high-frequency current clamp is measured the overall noise information separated is differential mode conducted noise information and common mode conducted noise information;

Spectrum analyzer, the output terminal of this spectrum analyzer noise separating network connects, be used for described differential mode conducted noise information and common mode conducted noise information are carried out computing in conjunction with the transfer impedance of described high-frequency current clamp, obtain differential mode conducted noise electric current and common mode conducted noise electric current.

Computing machine, this computing machine is connected with spectrum analyzer, is used for drawing radiated noise according to common mode conducted noise electric current by software.

Shown in accompanying drawing 5-7, concrete method of testing:

In time domain, its experiment connects as shown in Figure 5, this experiment utilizes signal generator to export the sinusoidal signal of different frequency in required measurement frequency range in a port of dual trace oscilloscope, simultaneously high-frequency current clamp is carried on the transmission line, the value that measures is input to the another one port of dual trace oscilloscope, according to 3 formulas, can obtain on different frequency point the transfer impedance of this current probe.

The noise separating network that is adopted is measured in the performance of radiation frequency range, can be applied in the middle of the estimating of radiated noise to determine this noise separating network.Judge that the good and bad leading indicator of common-mode noise separated network performance is that its common mode is inserted loss (CMIL) and its definition of differential mode rejection ratio (DMRR) as the formula (12):

$\mathrm{CMIL}=20\lg \left(\frac{V_{\mathrm{OC}}}{V_{\mathrm{CM}}}\right)$ $\mathrm{DMRR}=20\lg \left(\frac{V_{\mathrm{OC}}}{V_{\mathrm{DM}}}\right)---\left(12\right)$

Wherein, V _CMBe common mode input, V _OCBe common mode output; V _DMBe difference-mode input, V _ODBe differential mode output.In the common mode separated network, the ideal value that common mode is inserted loss should be 0, to guarantee that the loss of its common mode noise signal is less in the common-mode noise transmission; In like manner as can be known, its differential mode rejection ratio should be big as far as possible, can not be coupled in the transmission of common mode noise signal to guarantee its differential mode noise, so the ideal value of its differential mode rejection ratio should be-∞.By test, can obtain its common mode insertion loss and differential mode rejection ratio test result as shown in Figure 6.This result shows that this separated network can apply to estimating of radiation EMI frequency range.

At the test noise separated network on the basis of radiation frequency range performance, can the connecting circuit system.Digital gravimetric equipment is switched on, and high-frequency current clamp 1 is clipped on live wire and the ground wire; Another high-frequency current clamp is clipped on center line and the ground wire, to measure live wire noise and the center line noise V on the cable _L, V _NIts frequency that exceeds standard is 36MHz (as shown in Figure 7).The output port of high-frequency current clamp is linked in the noise separating network, with in the noise input spectrum analyser after separating to analyze the common mode noise current of single-chip microcomputer gravimetric equipment.

High-frequency current clamp is placed in different places on the digital gravimetric equipment cable, to determine the position of radiation maximum on the cable.Be divided into nearly power end in this case, mid point and nearly equipment end three places are detected, and its testing result is as shown in table 1:

The digital gravimetric equipment of table 1 Conducted EMI noise separation result

Filter location	Nearly power end	Mid point	Nearly equipment end
				The radiated noise amplitude	42dBuV	42.9dBuV	48dBuV

Shown in table, it suppresses the position should be at nearly equipment end place.

The foregoing description only is explanation technical conceive of the present utility model and characteristics, and its purpose is to allow the personage who is familiar with this technology can understand content of the present utility model and enforcement according to this, can not limit protection domain of the present utility model with this.All equivalences of being done according to the utility model spirit change or modify, and all should be encompassed within the protection domain of the present utility model.

Claims (1)

1. radiated noise test macro that is used for digital gravimetric equipment, comprising: the digital gravimetric equipment of single-chip microcomputer is characterized in that: also comprise:

High-frequency current clamp, a measurement ring in the high-frequency current clamp places on the live wire and ground wire of digital gravimetric device power supply (DPS) line, to extract in the digital gravimetric equipment in the power lead live wire overall noise information of line over the ground; Another measurement ring in the high-frequency current clamp is placed on the center line and ground wire of digital gravimetric device power supply (DPS) line, to extract in the digital gravimetric equipment in the power lead center line the overall noise information of ground wire;

Noise separating network, the input end of this noise separating network is connected with described high-frequency current clamp output terminal, and being used for high-frequency current clamp is measured the overall noise information separated is differential mode conducted noise information and common mode conducted noise information;

Spectrum analyzer, the output terminal of this spectrum analyzer noise separating network connects, be used for described differential mode conducted noise information and common mode conducted noise information are carried out computing in conjunction with the transfer impedance of described high-frequency current clamp, obtain differential mode conducted noise electric current and common mode conducted noise electric current.

Computing machine, this computing machine is connected with spectrum analyzer, is used for drawing radiated noise according to common mode conducted noise electric current by software.

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