Oscilloscope Probe Question

[CCB]

Hi Everyone,

I'm a scope newbie so forgive me if if I'm just asking a dumb question. I've got a new DS1054z (it came with 4x PVR2150 probes) and also purchased a Testec prob from RS specifically because it comes with a BNC adapter.

Now I connect a rigol PVR2150 and the Testec probes to the scope calibration signal and run auto and I get a nice square waveform after adjusting each probe.

My question is that if I 'zoom' in to look at the top of the square wave the rigol remains flat while the testec probe curves from the left lower the more I zoom in (gets alot worse the more you zoom in), why is that?

Here is the probe in question:    Testec TT-LF 312 Oscilloscope Scopemeter 15 MHz, 150 MHz 400 V, 600 V

Have I just ordered the wrong probe for my scope?


Thanks,
Carl

[Z80]

Try adjusting it whilst zoomed in, you should be able to make the left hand side of the pulse go both above and below the right hand side.  If you can't then it's likely your probe doesn't have enough adjustment range.

[tggzzz]

It is not a "scope calibration" signal, it is a "probe calibration" signal.

Have you adjusted the Testec probe's calibration in *10 mode?

When buying *10 "high" impedance probes (which aren't high impedance!), ensure the probe's calibration range (e.g. 10-25pF) encompasses the scope's input capacitance (e.g. 15pF).

For more info on probe, including references on which type to use and how to avoid using them dangerously, see https://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/

[David Hess]

The Testec TT-LF312 probe should work fine and that is a pretty unusual distortion from a probe.

Does the shape of the distortion change as the gain or position is changed?

It looks like the result of overload.  Most oscilloscopes recover from overload poorly and unpredictably.