All you need is few resistors and one of OPAMPs listed in the note. I used LT6200 and LT1806. You can purchased 0.1ohm and 0.01ohm 1% shunt resistors:
http://www.digikey.ca/product-detail/en/LVR03R1000FE70/LVRB-.10RCT-ND/1166532
Someone suggested me to use Current Transformer - there are transformers capable of few MHz bandwidth but I think transformers are more appropriate for higher currents.
Now you've replaced the problem of measuring current with characterizing your shunt. What's the inductance of that 10 mOhm shunt? At 10 MHz, even 1 nH of inductance will swamp that resistance.
I've wanted to purchase a current probe for my scope for some time, but the things are really very expensive. Even used ones, such as the Tek A6302, often sell for hundreds of dollars on eBay. Does anyone know why these things are so damn expensive?
Wayne
Same reason my friend says his divorce was so expensive: "Because it's worth it." Build one for yourself and you'll know why.
Speaking of expensive current probesb I just need a 90% discount
Forgive my ignorance, but (other than earth isolation) why not measure the current by sticking your probe across a shunt or something like Daves uCurrent?
Forgive my ignorance, but (other than earth isolation) why not measure the current by sticking your probe across a shunt or something like Daves uCurrent?
The Labdevice current probes are not expensive. Around 300USD. They measure AC and DC from the low uA range up to 1A. Perfect for electronic development.
www.labdevice.ch
There are just no cheap manufacturers like Rigol and Atten making these probes. They don't have the technology or R&D to pull this off.
Hi guys.
I think to buy some type of oscilloscope current probe. But I am not sure which type of current probes are more suitable for non isolated DC/DC or isolated AC/DC switching power supplies. It is possible to use pure AC current probe like TEK p6021 for example on buck (or bust converter) to test input ripple current or inductor current, or switching transistor currents current?
Are the AC+DC current probes are more preferable for examination of switching power supplies?
The Labdevice current probes are not expensive. Around 300USD. They measure AC and DC from the low uA range up to 1A. Perfect for electronic development.
www.labdevice.ch
How does this work then? Are the designers relying on the scope's front end attenuation & amplification circuitry? What voltages can be expected out of the probe transformer (also fed with bucking current)? AFAIR the output from the probe transformer is 50 Ohm, but some scopes with built-in 50 Ohm input impedance have relatively low input voltage range (like 5V RMS) so it worries me a bit.
If I can too skip attenuator & output amplifier then it would greatly simplify my DIY efforts.
AC probes like the Tek P6021/22 are terminated into either a amplifier (134) or a 1Mohm termination that encloses a compensation network and switchable attenuation, it is an entirely a passive module that allows for 2 levels of output.
IIRC 2mA/mV and 10mA/mV.
Modern DSO's have front end attenuation to match.
The format and circuitry is outlined in an old Tek booklet that has been linked here several times that I'm aware of.
http://www.davmar.org/TE/TekConcepts/TekProbeCircuits.pdf
19Mb
The Labdevice current probes are not expensive. Around 300USD. They measure AC and DC from the low uA range up to 1A. Perfect for electronic development.
www.labdevice.ch
Those are not proper current probes. If you read the datasheet it's just a shunt resistor with a diff amp across it so you don't get any isolation, you have to break the circuit you are measuring, they have a limited usable voltage range and you have to deal with the burden voltage of the shunt.