Hello guys!
I was reading this forum for a long time, but now I have a question, so this is my first post.
I am dealing with AVR microcontroller and NRF24L01 RF transmitter.
And I would like to measure its consumption.
The peak transmitting consumption of the whole circuit should be about 20mA, idling currents are sub mA.
I have a test circuit on breadboard and I am sending a packet every second.
But I have a lot of noise when measuring with uCurrent and scope - see the attachment.
Yellow line is output from uCurrent, blue is trigger signal from uC.
One is raw signal, other one is digitally filtered - the consumption footprint is corect.
I suspect the scope ground is giving me headaches.
I have uCurrent set on 1mV/mA.
If I measure uCurrent output with DMM (without scope attached) it shows like 0.2mV (of course it cannot detect transmitting pulses). This is correct measurement of idle current.
But when I connect probe positive end on Voltage output (+) on the uCurrent and scope ground on the (-), the DMM shows -11mV (negative!) If I connect just probe end or ground on Voltage output (+) it says -6mV or -16mV. So the connection disturbs the uCurrent output
Whatever scope probe end I hookup to Voltage output (-) on uCurrent it is still OK. DMM shows 0.2mA.
So the problem is in Voltage output (+) pin of uCurrent.
Something on the scope disturbs the output. Not just the ground, because also just the probe end disturbs it.
The circuit is powered through AC adapter with transformer, so it is isolated from scope ground.
What could it be?
If I have to explain further, just say it.
I sometimes overcomplicate my descriptions.
thanks