uCurrent Gold vs Current probe?

[Puffin]

I need to measure some current spikes.  I have an EEVBlog uCurrent Gold which I've used with my Tek scope for current measurements in the past with good success.   But I'm not clear on the true bandwidth of the uCurrent - what detail can I expect to see?  The alternative would be to get hold of a current probe (I'm considering the Tek TCP202A) but I'd like to better understand how much better performance (shorter current spikes) that would let me measure.

Any advice on this subject would be gratefully received.

[David Hess]

The MAX4239 used in the uCurrent Gold has a gain-bandwidth product of 6.5 MHz.  Operating at a gain of 100, that will yield a bandwidth of about 65 kHz.  A Tektronix TCP202A current probe has a bandwidth greater than 50 MHz so they are not even remotely in the same class.  They also have very different sensitivities.

So the uCurrent Gold is really only suitable for DC and line frequency measurements while the Tektronix current probe will work on switching power supplies.

[SilverSolder]

According to the uCurrent spec sheet, the bandwidth is > 300KHz  (3dB point).

It does this by having two op amps in series, with a gain of 10x each.

300KHz corresponds to a time constant of about 0.5uS...   so perhaps we can say it should be possible to see a 5uS pulse at reasonable resolution with the uCurrent.

I use my uCurrent for all kinds of crazy measurements, it is surprisingly useful to have a floating battery powered x100 amp.

Try it on a signal generator and see what you get?

[David Hess]

The uCurrent *Gold* schematic I checked showed only a single x100 non-inverting gain stage.

[SilverSolder]

This one?

 uCurrentRev5schematic.pdf (121.94 kB - downloaded 95 times.)

[David Hess]

This one?

No, that is not the one I saw but it really does not matter.  Slightly faster than 300 kHz is still very slow compared to a Tektronix current probe and not suitable for a switching power supply application.