0
\$\begingroup\$

I want to create a 50Hz noise on signal transmission line options which are a coaxial cable with BNC connectors and the other is an STP cable with BNC connector. Cables are like 10 meters long or more.

As receiver system I have two data-acq. systems, where one is single-ended input and the other is diff-input.

Imagine the output impedance of the source is balanced or neglect it.

So there are four combinations:

Coaxial to single ended daq

Coaxial to diff ended daq

STP to single ended daq

STP to diff ended daq

I want to experiment and demonstrate these in case of 50Hz interference.

But I dont know how can I create 50Hz interference on the lines.

How can I couple a significant 50Hz magnetic inference to a cable in practice? Is there an easy practical way?

\$\endgroup\$
0
\$\begingroup\$

How can I couple a significant 50Hz magnetic inference to a cable in practice? Is there an easy practical way?

I don't know about an "easy" way but you could use a three winding transformer with windings in series with signal and return wire (shield/screen) and the third winding excited with a 50 Hz voltage: -

enter image description here

You can "inject" at the source end or the receiver end to suit the configuration of your cables. The circuit above creates a common-mode voltage and that is what I believe you are looking for.

The signal source (50 Hz) needn't be connected to earth - it can be isolated but it was convenient to show it this way. The signal source could be the low voltage output from a seperate mains powered transformer.

\$\endgroup\$
  • \$\begingroup\$ Could you also add an illustration for the coaxial case? Im asking because this is a bit higher voltage stuff. Thanks \$\endgroup\$ – floppy380 Mar 14 '18 at 13:47
  • \$\begingroup\$ Are the terminals of 50Hz source 230V line and neutral in your figure? \$\endgroup\$ – floppy380 Mar 14 '18 at 13:48
  • \$\begingroup\$ No more pictures - you interrupt the screen/shield of the coax. The 50 Hz voltage signal can be anything you want but bear in mind safety and the step-down ratio you need to obtain the CM signal you require. \$\endgroup\$ – Andy aka Mar 14 '18 at 14:03
  • \$\begingroup\$ I will try these \$\endgroup\$ – floppy380 Mar 17 '18 at 15:43

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.