Capgo datalogger, data logger, datalogging and data logging.




Shielding from noise

Shielding in this context refers to the mechanism by which cables and equipment is protected from the effects of electric fields. It excludes the shielding from magnetic fields and the environment. Electric fields result when there exits a voltage difference between two points. Except in extreme cases, DC voltages are not a problem. Most problems occur with coupling of AC voltages into sensor cables.

Electric field coupling

Electric fields are coupled into sensor cables by the mutual capacitance between the sensor cable and the voltage "source". (The term source is used with caution. It takes two to tango - it is the voltage between two elements that is important.)

Magnetic field coupling

Magnetic field are coupled when a changing field occurs within a loop of the signal carrying conductor. It is extremely difficult and expensive to effectively shield. A better solution is avoidance by removal from the field and by minimizing the loop area.

Radio frequency shielding

High frequency (and often high energy) radio signals are easily coupled into signal cables and their shields. Modern semiconductor circuits are very susceptible to this type of interference largely due the rectifying effect of fast parasitic diodes within the chips. The symptoms are dc offsets that come and go.