Testing a used oscilloscope - wall outlet okay?

[Scott]

I just purchased an oscilloscope on Ebay, and I want to test it when I
get it. However, I haven't purchased a function generator yet, nor do
I have any oscillating circuits of my own.

Is it safe to monitor the 60Hz AC signal from a wall plug to test it?

Logic tells me yes, it is safe with reasonable precautions, that the
scope was designed for such measurements. However, my gut instinct
tells me that essentially sticking scope probes into a wall outlet is
a stupid thing to do.

Could I have some advice on if this is okay, or if there is a better
way to test it's functionality?

Thank you,

-- Scott

 

[CFoley1064]

Subject: Testing a used oscilloscope - wall outlet okay?
From: calicojack565@yahoo.com (Scott)
Date: 3/16/2004 8:27 PM Central Standard Time
Message-id: <5e2d44a1.0403161827.1c2bd1e4@posting.google.com

I just purchased an oscilloscope on Ebay, and I want to test it when I
get it. However, I haven't purchased a function generator yet, nor do
I have any oscillating circuits of my own.

Is it safe to monitor the 60Hz AC signal from a wall plug to test it?

Logic tells me yes, it is safe with reasonable precautions, that the
scope was designed for such measurements. However, my gut instinct
tells me that essentially sticking scope probes into a wall outlet is
a stupid thing to do.

Could I have some advice on if this is okay, or if there is a better
way to test it's functionality?

Thank you,

-- Scott

There are probably better ways to test scope functionality, starting with the
output reference signal available on the front panel of the scope (usually
something like a 1KHz 0.1V p.p. square wave). After that, try setting up a 555
timer, looking at some of the signals available from your stereo, and other
things. If you've got a real yen to check out 50/60 Hz signals, just hook up a
transformer and read the output. Keep in mind that line voltage is either
+/-170 V peak or +/-340 V peak. Read the manual, and look at the rating on the
scope probe, before you check out the line voltage.

Good luck
Chris

 

[Michael Black]

Scott (calicojack565@yahoo.com) writes:

I just purchased an oscilloscope on Ebay, and I want to test it when I
get it. However, I haven't purchased a function generator yet, nor do
I have any oscillating circuits of my own.

Is it safe to monitor the 60Hz AC signal from a wall plug to test it?

Logic tells me yes, it is safe with reasonable precautions, that the
scope was designed for such measurements. However, my gut instinct
tells me that essentially sticking scope probes into a wall outlet is
a stupid thing to do.

Could I have some advice on if this is okay, or if there is a better
way to test it's functionality?

Thank you,

-- Scott

No, you don't want to merely stick the probes in the wall outlet.

One of those leads will be ground, and stick it in the wrong one,
and you short the AC line to ground.

I knew better, but I once hooked a VTVM to an AC/DC TV chassis, and the
ground lead just burned up. That's what will happen if you just
stick the leads in the AC socket.

As someone said, a transformer will provide the needed isolation.

Or there are any number of ways to throw together an oscillator for
testing.

For that matter, scopes are sensitive, and by merely touching the
tip of the probe, you will see 60cycles picked up from indicental
radiation. That's always as easy way for checking a scope.

Michael

 

[Scott]

Thanks everyone for the helpful advice. The wall wart idea is a good
one. I also didn't know that scopes had a reference signal; that
should help as well.

-- Scott

 

[Dominique]

"Scott" <calicojack565@yahoo.com> a écrit dans le message de
news:5e2d44a1.0403161827.1c2bd1e4@posting.google.com...

I just purchased an oscilloscope on Ebay, and I want to test it when I
get it. However, I haven't purchased a function generator yet, nor do
I have any oscillating circuits of my own.

You can find signal generator software for PC that use the soundcard. You

can change waveform and frequency up to 20 KHz.
There is one here:
http://www.innerworlds.50megs.com/shakti/members/members/tech/Sig-gen.exe

but you can find many others.

Dominique.

 

[robin.pain@tesco.net]

calicojack565@yahoo.com (Scott) wrote in message news:<5e2d44a1.0403161827.1c2bd1e4@posting.google.com>...

I just purchased an oscilloscope on Ebay, and I want to test it when I
get it. However, I haven't purchased a function generator yet, nor do
I have any oscillating circuits of my own.

Is it safe to monitor the 60Hz AC signal from a wall plug to test it?

Logic tells me yes, it is safe with reasonable precautions, that the
scope was designed for such measurements. However, my gut instinct
tells me that essentially sticking scope probes into a wall outlet is
a stupid thing to do.

Could I have some advice on if this is okay, or if there is a better
way to test it's functionality?

Thank you,

-- Scott

Touch your probe. You are seeing the mains picked up by your body (the
same hum your hear when you touch the input jack of your guitar amp).

Set the Y gain to maximum. Move your probe around the front back and
sides of your monitor or TV (switched on) (leave the earth dangling).

You are seeing pulses from the "line oscillator" i.e. the device that
drives the CRT spot from left to right.

Try flicking the trigger select about. It is more likely to "lock" on
"TV synch" or "line" (twiddle the trigger level).

Robin