Special reminder:
This link is only a probe, does not include SMA connection, SMA turn N head and so on.
PCB Simple EMC Near Field Magnetic Field Probe (Model III V500):
Large, medium and small magnetic field probes and electric field probes are mainly used for EMI space radiation rectification.
The magnetic field probe type III is mainly used for conduction rectification of EMI.
Extra large: The probe part is about 5 cm in width and 3.2 mm in thickness.
Big size: The width of the probe is about 2.1 cm and the thickness is about 3.2 mm.
Medium size: The probe is about 1.4 cm in width and 3.2 mm in thickness.
Trumpet: The probe is about 1.0 cm in width and 3.2 mm in thickness.
Electric field probe (Type I): The length of the probe is about 10 mm and the thickness is about 1.6 mm.
Improvement of Type III magnetic field probe (relative to Type I):
1. Full shielding structure is adopted to greatly suppress electromagnetic clutter interference in the external environment and improve the dynamic range of the whole system.
It is helpful to improve the accuracy of position detection, and the handle part is shielded to reduce the influence of human hands on the probe.
2. Wider bandwidth. In theory, it can achieve frequencies much higher than 7GHz, and its performance is unknown due to the limitation of testing equipment.
The working bandwidth of large, medium and small magnetic field probe: 1MHz-7GHz
Measured Frequency Response Map (Large, Medium and Small Size) (1MHz-7GHz)
Ultra-large bandwidth: 9KHz-90MHz
Measured Frequency Response Map (Ultra Large, Low Frequency Probe for Conduction Correction) (9KHz-90MHz)
Frequency Response Diagram (Ultra Large, Low Frequency Probe for Conduction Correction) (10KHz-2MHz Simulation Diagram):
The efficiency of oversize is very low near 10KHz. If it is used to detect ultra-low frequency, the noise level of your spectrometer should be less than - 130dBm. Comparing the measured and simulated frequency response diagrams, we can find the measured results of the efficiency of the oversize probe in the low frequency band.
Better than simulation, about 20 dB upgrade.
Type III probe adopts full shielding structure to effectively suppress the external stray electromagnetic field interference.
In the following figure, a practical comparison between Type III and Type I in restraining stray electromagnetic field interference is given. Type III and Type I probes are in the same electromagnetic environment. From the purple line (type I frequency response curve) in the figure, it can be seen that stray electromagnetic field in the environment raises the noise level of the whole system and reduces the dynamic range of the system.
Regarding Type I and Type III, my suggestions are as follows:
Beginners please choose type I probe. Because the sensor of type I magnetic field probe (large, medium and small) is bare (without shielding), it not only receives magnetic field signal, but also electric field signal. It gives people a better sense of sensitivity. I think it should be called electromagnetic field probe in theory. The disadvantage of Type I is that it is easy to be disturbed by electric field signals in external environment.
Type III magnetic field probe adopts full shielding structure, which greatly restrains electromagnetic clutter interference in the external environment. It is a true magnetic field probe.
Usage method:
Type III probes are strongly recommended for amplifier use.
1. If your spectrometer is older and does not have a built-in preamplifier, it is recommended to have an RF amplifier with an amplification factor of about 30 dB.
Diagram of the connection between probe, amplifier and spectrum analyzer:
If the noise level of your spectrometer is less than - 110 dBm or if you have a built-in preamplifier, you may not need an external preamplifier.
Connection diagram of probe and spectrum analyzer (with built-in preamplifier):
The magnetic field probe is used to detect the magnetic field near the circuit board, and the magnetic field probe can also be used to detect the leakage of magnetic field in the gap of the cabinet. In order to make as many magnetic field lines pass through the probe loop as possible, the magnetic field probe keeps the same current flow direction when used.
The electric field probe (non-contact type) is used to detect the near-field electric field. The probe is perpendicular to the conductor when the near-field electric field probe is used.