I have a medical office call box/light system that is older probably 20 year old and they moved the main panel that the Drs see to know when there are patients waiting and since they moved it, it is intermittently not working. The system uses a siginal that is transmitted over the AC connection/plug.
I am new to oscilloscopes but purchased one to see if I could observe if the siginal is too weak in the new location (it’s about 250 feet from where it was originally) or if it’s getting too much interference.
I have found that the system needs to be on its own circuit and have a 2700 UH choke installed on the circuit feed but that’s about all I can come up with since apparently the manufacture has gone out of business. They do still have a website but only very limited information and no schematics.
http://www.varitronics.com/ts-cs2install-nc.htm
My problem seems to be when I look at the pattern all I can identify is the 60hz siginal and don’t see any changes when energizing one of the boxes and would like to know if anyone has any suggestions for blocking out the 120V 60Hz siginal so I can see the siginal that is used to operate these boxes over the 120V line. I believe I need a high pass filter but not sure what components I would need to achieve blocking the unwanted siginal but still be able to pass the triggering siginal I am looking for to identify the problem.
Thanks in advance for any help you may be able to provide.
Hello mech11,
I agree with you, that moving the light box 250 feet from where it was originally could cause the signal to be weaker. If you're able to tell me the specs of the wire (make/model/type) I could tell you the loss created by the wire.
There are a few question I have upon reading your question:
What is the model of your oscilloscope?
Where on the schematic are you attaching your probes?
What is the voltage of the signal you are seeing on your scope? It seems unlikely that AC power is being transmitted to the light boxes, and more likely that the 60 Hz signal you're seeing on the scope is noise from fans, lights, or power supplies.
The filter you're looking for is called a notch filter. It has the following response:
It's dangerous to make your own filter and connect it to power main. I would recommend contacting an electrician if it is truly 120 V AC @ 60 Hz. This voltage and frequency is very fatal to humans if directly exposed.
I await hearing back from you!
Jonathan Falco