How to Track EMI Emission Source by Spectrum Analyzer

Spectrum analyzer is a more suitable instrument for measuring EMI. Spectrum analyzer is the instrument displaying voltage amplitude change with the frequency and its waveform called spectrum. Spectrum analyzer overcomes the shortcomings of oscilloscope in measuring EMI and it can accurately measure the EMI at each frequency and directly display the signal spectrum components.

Below is the introduction of how to use nearby probe and spectrum analyzer SA9275 or SA9115 to test nearby EMI.

Nearby probe includes: EMI electric field probe and EMI magnetic field probe.

 

Figure 1. Nearby Probe Set

Test methods:

Set spectrum analyzer's sweep range and analyzing bandwidth according to the interference frequency.

The corresponding relationship between sweep range and analyzing bandwidth are as follows:

 

Sweep range	Analyzing bandwidth
9kHz~150 kHz	200Hz(6dB)
150kHz~30MHz	9kHz(6dB)
30MHz ~1GHz	120kHz(6dB)
>1GHz	1MHz(3dB)

 

To set the Spectrum analyzer's sweep range, you need press【FREQ】firstly and then set Starting frequency and Stop frequency.

To set the analyzing bandwidth, you need to press【BW】firstly, and then input the needed bandwidth which should be within the range of this instrument.

 

Figure 2. SA9275 EMI Test

Figure 3. SA9115 EMI Test

How to Use Bench-top Digital Multimeter?

Multimeters are one of the necessary instruments for hardware engineers, they can measure voltage, current, resistance, capacitance, diode, etc. Nowadays, portable multimeters and clamp multimeters as common ones in the market, and it is rarely known by people how to use bench-top multimeters. Now we'll briefly introduce it by taking Suin SA5053 digital multimeter as a sample. Hope it will do some favor in your everyday's testing and measuring work.

The using method of bench-top multimeters and portable multimeters has some differences, although the basic principle is the same. Actually, it is very easy to use bench-top multimeters. There is a red terminal in the red testing lead, and a black terminal in the black testing lead, which is the same with common multimeters, red test lead is positive polarity, black test lead is negative. This test lead kit will be used during parameter measuring.

Before using it, the Null setting is the first step to do which is can't be ignored. Then choose the suitable parameters to test according to the under-tested component or instruments. Eg., to test DC voltage, the DCV function should be chosen in SA5053, while not other functions like DCI, ACI, resistance, or capacitance. Please be noted to choose the suitable voltage range to test. If the voltage of the under-tested instrument is out of range, SA5053 can't display the testing result and may be burned. After everything is set OK, contact the positive and negative polarity by red and black test lead kit stably, and the measuring result will be shown in the SA5053.

Some tips for users when using digital multimeters are as followings:

1. Please read User's Manual carefully before using it to learn the function keys and measuring range.

2. Make sure to set suitable function and range, input voltage or current shouldn't be surpassed the maximum range to protect the internal circuit from being damaged.

Figure 1. SA5053 testing power adapter's voltage

 

Figure 2. SA5053 testing current

 

Figure 3. SA5053 testing temperature

 

Figure 4. SA5053 testing resistance

 

Figure 5. SA5053 testing capacitance

 

Please contact Suin for more information about SA5053 digital multimeter.