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Is it safe to probe a mains-to-24v transformer with a DSO?

Former Member

Hello,

 

I am working on a video project where I must measure and explain a sinusoidal relationship, and I have chosen electricity. I figured the best method of demonstrating and measuring alternating current is with my HP Agilent 54645D Mixed Signal Oscilloscope. The probes I am using are rated for 600 volts. However, based on some common sense as well as multiple horror stories on the end, I figured that hooking my scope up directly to the 125VAC mains in my house was a terrible idea...so I dug out a kit power supply I built a few years back.(link below) It's 0-12V and uses an LM317 for regulation, so I figured it would be around 12-24v on the output of the transformer. I was correct. Upon measuring with my multimeter, I found that it outputs 24VAC.

 

Now, my question is, is it safe for me to probe the output wires on the transformer, or will I need some form of insulation? I am fairly new to alternating current in general. While the supply does not plug into mains earth, I have heard that neutral is earth referenced(again, humor me on my lack of knowledge) and I do not want to risk blowing my probes up by creating a short to earth.

 

I would appreciate that some of you refrain from the old "If you need to ask, don't do it." remark. I want to figure this out, even if there is some extensive learning involved.

 

Thank you,

 

Tom

 

 

 

The kit supply: 0-12V 1AMP VARIABLE POWER SUPPLY KIT-Chaney Elecronics

  • Hi Tom,

    The 24 VAC is isolated from the mains and should pose no problem for your scope to look at. Also the 24 volts should pose no danger to you if you should touch it. I am assuming that your Primary (Mains) are properly insulated and since you built the supply you know where they are. Since the 24 volt secondary is isolated you can hook either lead to the scope ground and your probe to the other lead.

    John