Differential Probe

I use a battery operating scope that is all insulated with a 2Kv 250Mhz probe that only cost me 100 bucks..

THat probe you are looking at does not have enough head room in my opinion.

But, that is just my opinion.

Jamie

Hi,

What should I do? I am stuck with this oscilloscope.

Melissa

"melissa walraven"

** More info - is this voltage referenced to ground or across two points in a circuit ? ** The scope can show 80V p-p on the screen and so with a 10:1 probe will show 800V p-p. ** Nope.

Probes like that very expensive one are for viewing small differential voltages in the presence of a large voltage to ground.

Why don't you explain what you are really trying to do ?

... Phil

if this source you're trying to measure has a common to earth and you are trying to measure between to points with in, then I would use 2 Hv 100:1 2KV type probes.. USe channels A and B with the math functions to get a differential between the two.

One thing to note, you may want to check the common on your scope's probe BNC in the docs, it is very possible you have isolated inputs. I own a Regal but I never checked that so I can't be sure.

If you do, you still need a HV probe.

I do own a hand held cheapy scope that does have isolated BNC inputs and I can directly connect between to points in HV land using the 2K probe I have.. And this is a OWEN 20 mhz scope I do this with.

So you may want to check your scope docs.

JAmie

I am trying to measure the voltage across a capacitor in a RC circuit. Can this scope do diffenertial measurment with out differential probes using Channel A - Channel B option?

Melissa

No, it won't. Read the datasheet.

Only problem is that. since you don't have a TekProbe scope, you will need an 1103 power supply to go with it, costing 2200 bucks, on top of the $1320 for the probe.

Does the Rigol have an A-B facility? If so, a couple of 1000V x100 probes would be considerably cheaper.

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)

If it has that facility, yes. You'll still need high voltage probes, though.

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)

OK hopefully people on the group will 'correct' me if I say something stupid.

1.) 300Vrms is a bit more than 800Vp-p. (But not much head room left) 2.) With a x10 probe the input to the 'scope is cut down by a factor of ten, so as long as the x10 probe can handle the voltage it should be OK. (Phil A mentioned this already.) You should read the spec's on your rigol probes. 3.) Can you make a resistor voltage divider to bring the voltage down to 'human safe' voltage levels. I hate hooking in to HV stuff.

George H.

Yes but you need HV probes, which are a lot cheaper than what you were looking at.

Look for a couple of cheap 100:1 2KV scope probes.

You use the Subtract function in the scope to get the difference via the two channels.

Jamie

Should this be: '*does not* have a common to earth'?

--Winston

Hi,

Will this be an appropiate probe

I am trying to measure atleast 800 Volts acorss the capacitor. I am unable to understand that does this scope can do differential measurement using MATH option A - B. I read the user manual but unable to understand.

melissa

You apply the A probe to one end, and the B probe to the other end, then A-B is the *difference* between the ends.

That's what "differential" means.

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)

=A0 =A0(Richard Feynman)

Where should I connect the Ground of the probes?

melissa

(...)

Both go to the common ground return of your circuit. You will not need a differential probe if one end of the capacitor is already grounded.

--Winston

To any convenient zero volts point, If the scope's common mode rejection in subtract mode is good enough, which I doubt, you might get away with leaving hem floating.

You *must* make sure that both probes are properly compensated with their respective inputs. That really affects common mode rejection.

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)

One end is connected to source and the other end is connected to resistor.

melissa

Life would be very much easier if we had a good idea of the circuit you are using. Please consider using either AACircuit or LTSpice to post an asciimatic?

View in Courier font:

___ Vdd---|___|-----. | | | ||-+ ||

--
This is fairly late to be mentioning that there's a resistor in there
too.

Can you post a sketch of your circuit, please?