Checkpoint LAB USB-RS232 Manuel d'utilisateur télécharger pdf (Page 24)

STEP 5. NOISE IMMUNITY CONTINUED

HOW DOES NOISE GET INTO ELECTRONICS?

Energy Coupling

(Conductive, Inductive, Capacitive)

• EMI - Current surges

(ElectroMagnetic Interference) An electrical disturbance in a

system due to natural phenomena, low-frequency waves

from electromechanical devices or high-frequency

waves (RFI) from chips and other electronic devices.

Allowable limits are governed by the FCC.

• RFI – high impedance devices requiring very

limited current.

(Radio Frequency Interference) High-frequency electromagnetic waves that

emanate from electronic devices such as chips.

If the source is sufficiently strong this can enter your circuit.

STEP 5. NOISE IMMUNITY

design solutions

Protect from?

• ESD

• Solution: Proper grounding, optical isolators,

capacitors

• Transients

• Solution: Low pass filter, optical isolators,

software sampling

• Reverse polarity

• Solution: Diode circuits to protect against,

fuse.

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Checkpoint LAB USB-RS232 Manuel d'utilisateur Page 24