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Measurement Method Of Conduction Interference Of Oscilloscope
- Apr 23, 2018 -

It is suggested that the conduction interference measurement be carried out in the shielding chamber.

In the range of 0.15 ~ 30MHz, the measuring receiver with quasi-peak and mean detector is used for measurement. The two detectors can be contained in a receiver. During measurement, the quasi-peak detector and the mean detector are used alternately. In order to save time, peak measurement can be used to replace the quasi-peak measurement and average measurement. In case of a dispute, the quasi-peak measuring receiver should be used when measuring the threshold value. When the average value is measured, the receiver should be measured with an average.

1. Measuring receiver

The quasi-peak measuring receiver should meet the requirements of CISPR 16-1:1993, and the average measurement receiver should meet the requirements of CISPR 16-1:1993, and have the 6dB bandwidth required by CISPR 16-1:1993. The peak measuring receiver should meet the requirements of CISPR 16-1:1993 and have the 6dB bandwidth required by CISPR 16-1:1993.

2. Artificial power network.

In order to be in power at the ends of the feeder terminal voltage provided on the measurement point of high frequency impedance, and the circuit under test and the background noise isolated on the grid, you need to use artificial mains network (AMN). Should use CISPR 16 - and 93 sets of 50 Ω / 50 mu H artificial mains network.

Between the phase line and the reference ground line and between the middle line and the reference ground line, the two measurements should not exceed the corresponding limit.

Conducting ambient noise coupled from local broadcasting facilities may make it impossible to measure at certain frequencies. At this point, a suitable additional rf filter can be inserted between the artificial power network and the power supply, or the measurement can be completed in the shielding chamber.

3. Grounding plate

Desktop devices under test should be put in the size of 2 m x 2 m vertical reference ground tablet 0.4 m in the distance, and should be with the other part does not belong to the device under test the tablet to keep any metal surface or ground 0.8 m distance. If the measurement is carried out in the shielding chamber, the above 0.4 meter distance can be the distance from any side wall of the shielding chamber. If the measurement is on the open field, the distance of 0.4 meters is the distance from the horizontal metal grounding plate.

The device should be placed on a horizontal grounding plate. Contact of each point is consistent with the normal use, but can not contact with the ground plate forming metal, reference ground plate shall be at least 0.5 meters larger than the border around the device under test, and the most careful size is 2 m x 2 m.

The artificial power network and the impedance stable network are connected to the reference grounding plate by the shortest possible conductor.

Connect the power port to the artificial power network through the power cord; The telecommunication port is connected to the impedance stable network through the signal line.

4. Conduction interference measurement of telecommunication ports.

Measurement of common mode interference from the telecommunication port of the tested equipment. Useful signals may form common mode interference. In the design stage of the interface process, if the signal parameters of the telecommunication port are given due consideration, the interference caused by useful signals can be controlled.

(1) qualified test method.

(2) impedance stability network:

The power supply voltage of the tested equipment shall be provided by the artificial power supply network used in the measurement of the interference voltage of the power port. In balance with the shielding in line telecommunications ports, application of cable connects telecom ports and impedance stable network test, to evaluate the telecommunication port (asymmetric) common-mode interference voltage or current, therefore in the process of test, looking over the telecommunication port of common mode impedance stable network terminal impedance. The impedance stability network shall not affect the normal operation of the tested equipment and can be inserted into the signal cable between the tested equipment and the load.

At present, it is not possible to specify a universal impedance stability network because the structure of the impedance stable network depends on the configuration of the measured telecommunications port.

The impedance stability network shall have the following characteristics:

* in the frequency range of 0.15 ~ 30MHz, the common mode terminal impedance is 150, plus or minus 20, and the phase Angle is 0, plus or minus 20.

* should be able to provide enough isolation, to isolate those who are connected to the telecommunication port being measured from the interference of the load, the common-mode voltage interference or interference from load current, impedance stable network attenuation should be: measured at the receiver input interference should be lower than the corresponding limits of 10 db.

* the attenuation distortion or other loss of the signal quality in the useful signal band caused by the insertion of the impedance stable network should not significantly affect the normal operation of the device under test.

* if the voltage measurement port on the impedance stable network is available, the accuracy of the partial pressure coefficient should be within + 1dB. After partial pressure coefficient should be inserted into the impedance stable network present in the device being tested on common mode impedance voltage and rendering on impedance stable network connection port measurement receiver at the input voltage difference. Such as, common mode impedance is 150 Ω, receiver input impedance of 50 Ω, electricity of subsection pressure coefficient of 20 lg (50/150) = 9.5 dB.

(3) measurement:

For the shield connected to the line of telecommunication port conducted interference voltage measurements, apply a stable impedance network, the impedance network can provide a suitable connected to the measuring receiver port voltage measurement, and can meet the requirements of telecommunication port common-mode terminal impedance.

A suitable impedance stable network for two lines should be used in the measurement of the transmission interference voltage of the telecommunication port connected with a single non-shielding balance. When conducting interference voltage measurement for non-screened cables containing two sets of balanced pairs, a suitable impedance stable network for four lines should be used.

With the shielding (single balance to the line to line or two groups of balance) to the line connecting the telecommunication port conducted interference electric current measurement, should press the conduction disturbance voltage measurement termination cable in the same way.

For the measurement of the transmission interference voltage of a telecommunication port connected with a shield or coaxial cable, the measurement method... .

For the measurement of the interference current of the telecommunication port connected with the shielding or coaxial cable, the measurement method... .

5. Measurement record

Of equipment to be tested every power terminal or telecom ports, for more than 20 db L - (L threshold level for a logarithmic units) interference level, which shall be recorded in at least six largest interference level and the corresponding frequency. For the power terminals, record the measured values on a daily load line respectively.