advices for connecting an oscilloscope to CR

[topor]

Hi There, I haven't used this device for a long time and I'm very novice now. I turn it on after 4 years and battery still alive!!, great work !!

I want to measure the charging current and ripple from some capacitors connected to a AC source with a rectifier diode picking only the positive half-cycle of the AC voltage (about 0-20V) . not sure if that is relevant but don't know if I need to use the DC mode or BIAS mode, also I understand I should use the  SUPPLY / DUT  terminals as usual...right?

I don't have an USB isolator or the bluetooh module, so just looking the screen it's not going to be so useful, I would like to connect an osciloscope but I don't have a single clue of how/where connect it, also any tips for the osciloscope (sds1104x) configuration would be helpfull. I have read some ground loops problems and now  I'm afraid I might break it (both CR or OSC)

If helps..The AC supply is just a motor as a generator, so no plugged into anything of the house

Thanks

[Felix]

Hi topor,

The CR input positive terminal should ALWAYS receive the current directly from the power source and then the negative terminal should then feed it into your device/DUT.
The output terminals will produce a waveform that is proportional to the current used. This also has a "positive" and "negative" (or "signal" and "ground") and you can test it with a DMM or scope.
If the current can be negative (ie. an AC current), then the BIAS mode can be used to see the waveform entirely and not just chopped off.

If the scope is plugged into the same mains that powers your motor or DUT, then that's a problem and it will create a ground loop which can damage the CR. This is also true if you connect the CR to a computer which is on the same mains power as the DUT or oscilloscope or anything else in the combination.

[topor]

Thanks Felix for your reply, I understand perfectly.

Just to be sure, the motor is powered by a battery so no plugged / powered  from anything outside that source, it that still safe?
About the waveform.. I guess if I'm in mA range, 1mV on the scope will equal to 1mA?

By the way, the firmware must be whatever was in 2019/2020, I find the way to updated a bit tricky for my skills, can I keep on that (whatever) version or do you recomend to updated it due to some major bug or glitch?

[Felix]

Yes if your DUT is battery power, that's great.
Yes 1mV = 1mA, it is mentioned on the silkscreen of the CR.
If the CR works to your expectations, then no reason to upgrade the firmware.

[topor]

So many thanks for your help, I just tried it out and works like a charm 

Just one last question. It's the measuring / waveform mirror feature involving any mcu o post process that may be restricted to any sample rate? my idea is to measure a 1Mhz switching converter and not sure if I will "miss" any event as CR will miss aswell

Thanks

[Felix]

That's if you use the USB sampling which is processed by the MCU and has a lower sampling rate compared to the raw signal.
The OUTPUT terminals will output a raw result waveform, whatever the output from the internal opamps is.

[topor]

Sweet!! Thanks