FAQs-GW Instek

Q1

If my GFG-8255A fuse burns out, how do I replace it?

If the fuse is burned out, the instrument will not operate. First find out the cause of the fuse damage and correct it, then replace it with the correct value and type of fuse, as shown in the following list:

Model	Fuse values and types		Input value
Model	115V	230V	Watts	VA
GFG-8215A	T 0.315A 250V	T 0.16A 250V	22	28
GFG-8216A	T 0.315A 250V	T 0.16A 250V	25	32
GFG-8217A	T 0.315A 250V	T 0.16A 250V	27	34
GFG-8219A	T 0.315A 250V	T 0.16A 250V	29	36
GFG-8250A	T 0.315A 250V	T 0.16A 250V	25	32
GFG-8255A	T 0.315A 250V	T 0.16A 250V	29	36

Note: To prevent danger, be sure to replace the 250V fuse and cut off the power supply before replacing it.

More Porduct information: Spectrum Analyzers

Q2

How to understand that time domain and frequency domain are two sides of a signal?

A ridge across, a peak sideways; far, near, high, low, no shapes alike; one can’t see Mt. Lu’s true nature; since one is in the mountain. Written on the Wall at Xilin Temple by Su Shi.

I believe that electronic engineers should have the same feeling when learning signals. The more they learn, the less they understand.

Time domain, frequency domain and modulation domain just observe signals from different aspects.

Taking FSK as an example, what you see in the time domain is a sine wave with frequency changes, what you see in the frequency domain are two frequencies (ideally), and what you see in the modulation domain are changes in High and Low digital information.

The signal jitter seen in the time domain is phase noise in the frequency domain.

To observe the frequency domain on a time domain oscilloscope, you can use FFT (Fast Fourier Transform).

To observe the time domain on a frequency domain spectrum analyzer, you can use the Zero Span setting. The amplitude dynamic range of a spectrum analyzer is wider than that of an oscilloscope, which is suitable for viewing large and small signals at the same time. It can provide better amplitude resolution and accuracy when measuring signal and noise amplitudes simultaneously.

Therefore, to reveal the true nature of the signal, we can observe it from these three aspects (time domain, frequency domain, and modulation domain).

More Porduct information: Spectrum Analyzers

Q3

What are the basic differences between a Spectrum Analyzer and an Oscilloscope?

If we use the three axes of time, frequency, and amplitude, we can define three domains.

The spectrum analyzer is an instrument representative of the frequency domain (the relationship between frequency and amplitude). The vertical axis of the display is amplitude (power) in dBm, and the horizontal axis is frequency in Hz.

The oscilloscope is an instrument representative of the time domain (the relationship between time and amplitude). The vertical axis of the display is amplitude (voltage) in V, and the horizontal axis is time in S (seconds).

Digital oscilloscopes can convert time domain signals into frequency domain through fast Fourier transform. However, due to the insufficient vertical dynamic range of oscilloscopes (usually 8 bits), spectrum analyzer is still required to accurately measure the amplitudes of harmonics and noise.

Modulation domain analyzers (Modulation domain) display the relationship between time and frequency. Frequency counters with fast measurement speed can depict modulation domain waveforms through computers. Spectrum analyzers or the advanced FFT of oscilloscopes also have the function of displaying time and frequency.

More Porduct information: Spectrum Analyzers

Q4

Spectrum Analyzer Rack Mount Kit

GRA-415 Rack Mount Kit for GSP-9330 and GSP-9300B

GRA-415

Q5

What regulations do I need to meet signal receiving equipment used in testing EMI?

Signal receiving equipment for EMI testing is typically EMI receiver or EMI spectrum analyzer, which receives signals coming in through the antenna, probe or cable. Regardless of the EMI receiver or EMI spectrum analyzer, both must meet the following regulations:

- ±2dB absolute amplitude accuracy
- Filter (-6dB) that meets CISPR requirements, as shown in the table below:

Frequency band	Filter (6dB)
9k ~ 150kHz	200Hz
150kHz ~ 30MHz	9kHz
30MHz ~ 1GHz	120kHz
1GHz ~ 3GHz	1MHz

- Support Detector for EMI: Max Peak (PK+), Quasi-Peak (QP), EMI Average (EMI-AVG), RMS Average (RMS-AVG)

Q6

Why can't spectrum analyzers or EMI receivers observe transient interferences of electrostatic discharge?

Because spectrum analyzer and EMI receiver are narrow-band sweep receivers, they only receive energy in a certain frequency range at a certain time. Transient interference of electrostatic discharge is a kind of pulse interference, and its spectral range is very wide, but the time is very short. When an instrument produces transient interference, it is only a small part of its total energy that cannot represent the actual interference situation.

Q7

What is the QP time constant defined in the CISPR 16 Regulation?

CISPR 16 defines the regulations for EMI test equipment, as shown in the following table, which is the Receiver or spectrum analyzer for EMI measurement. The regulation characteristics must meet the requirements of the parameters. It mainly defines which Detector to be used in the measurement bandwidths and the corresponding time constants.

For an explanation of the various Detector differences, please refer to the video “Peak, Average and QP detectors” on YouTube.

Q8

Can GSP-9330 set a Limit Line of CISPR 25, a Limit Line with breakpoints?

GSP-9330 cannot perform editing, but the GSP-9330's dedicated PC software SpectrumShot can perform editing.

This PC software must be collocated with the NI VISA driver. Please download it from the NI website.

Q9

Does GW Instek have EN55025/ISO16750 automotive conducted EMI test kit?

The frequency band for automotive electronics testing in the conducted section is from 10 kHz to 108 MHz and the test must be collocated with a dedicated DC LISN. GW Instek GLN-5040A is a LISN that uses AC power and cannot be used for conducted EMI measurement of automotive electronics. However, GSP-9330 can conduct the above-mentioned test while collocating with a DC LISN of other brands.

Q10

Which power cable should I use for EMI testing?

A power supply cable with a magnetic ring can suppress conducted or radiated EMI by the characteristics of the magnetic ring.
The better the isolation, the better the power supply wire can suppress the EMI from radiating out of the power supply to form radiated EMI, but the cost is relatively higher.

Q11

Noise difference between Common mode and Differential mode.

Common mode and differential mode noise can theoretically be analyzed in conducted and radiated EMI. However, when it comes to the actual noise suppression technology, it is more meaningful to discuss the conducted noise. It is also possible to seek reference countermeasures through measurement. The following figure shows the common circuit for conducted EMI suppression in power supply. CY, LCM is a common mode noise filtering network, and CX is a differential mode noise filtering network.

If we can measure the common mode component and the differential mode component of the conducted noise separately, we know that we should adjust the common mode filter CY, LCM, or the differential mode filter CX to reduce the noise. The following is a brief description.

and

in the figure represent the currents on the two power lines. In theory, we can treat

and

as the sum of the common mode and differential mode noise currents, namely:

and

,

is common mode current,

is differential mode current.

Furthermore, we found that

and

can be obtained from

Comparing the two equations, as long as the signal of one of the power supplies can be added to the other power line signal in the forward and reverse directions, the sum and the difference of

and

can be obtained separately, and the

and

can be measured. Therefore, a

and

coupler/adder can be designed at the power supply terminal of the DUT to obtain

and

.

There is an approximation, which uses a current probe with a spectrum analyzer to measure the sum of the two power lines, as shown in the following figures.

In Figure (a), run two power cables through a current probe, connect the probe with a spectrum analyzer to obtain

. Run one of the power cables around the probe (b) to make the current direction opposite to the direction as shown in. (a). By so doing, the

can be measured from the spectrum analyzer, and the results are shown below. It can be seen that the common mode noise component is higher than that of the differential mode, and we know that the common mode filter

and

need to be adjusted to reduce the common mode noise component. Although this is not an accurate measurement, it is an approximation that is worthy of reference.

Common mode and differential mode noise

Q12

What is the timing of using Transient Limiter GPL-5010?

If users concern big signal fluctuation while conducting EMI testing, especially the spectrum analyzer might be damaged when using PR-01 to directly contact AC circuit, use GPL-5010 to protect GSP-9330, as shown in the following diagram.