Hello.
Maybe this is essentially the same question to previous question what I made, but I would like to clarify this. My questions are like this: What is the role of BNC terminator? (The terminator to BNC T adapter which other arm is for BNC cable connector. Maybe this is parallel type) and when it is used?
I've always wondered what they are although our lab has plenty of them:)
Dear Jang!
BNC terminator absorbs the electrical energy of the signal as it reaches the ends of cable and avoids reflection of signals. So it doesn't become noise.
Oh thanks Hanif Durad and Constantin Aniculaesei! Thus could you tell me one more how it is supposed to be used? For example, The BNC terminators can have several marked values such as 50 Oh, 75 Ohm, etc. What does it means that terminator itself has impedance of that value?
There are two major types of coaxial cables terminators: BNC type and F type. The BNC type has 50Ω impedance while the F type 75Ω. For low to medium frequency signals (ELF registration to oscilloscope) a 50Ω imp. is suitable (i.e. the BNC). For higher frequencies (like in TV signals, VHF, UHF etc) a higher impedance is suitable in order to have less reflection on the electromagnetic wave, thus the F type is right choise. When it comes to impedance it is the wave impedance of the line (the coaxial cable). Z = (Zo/2π sqr(εr)) *ln(D/d), where Zo = 376,73Ω the impedance of the free space, εr the dielectric permitivity of the material, D the ext. and d the int. diameter of the coaxial cable i.e the BNC connector. This impedance has nothing to do with the well known impedance of a line, when the electromagnetic waves are not taken into consideration (i.e AC electric circuits with f = 50 or 60Hz)
here is a very helpful video about this topic
https://www.youtube.com/watch?v=DovunOxlY1k
regards
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