Hello
The title of this thread is misleading , but I kept getting server errors so I had to change it.
Signal current using a DMM
I was trying to measure the current going out of a constant current driver with my DMM the other day ( feeding an led).
When I connected the TTL to +5volts (I'm powering the whole thing with 5V)
then I got a current of say 50ma , then without doing any adjustments I connected the TTL to the micro which was outputting a few tens of Khz square wave and the DMM showed more than twice the amount of current , about 120ma.
I understand that the DMM current mode is not designed to measure signal currents so this is an error right? When I give the TTL say.. a 50khz square wave then driver should output half the average current than if I connected the TTL to 5volts right?
Just want to make sure there isn't some trickery going on ...
Thanks in advance for the answers
The title of this thread is misleading , but I kept getting server errors so I had to change it.
Signal current using a DMM
I was trying to measure the current going out of a constant current driver with my DMM the other day ( feeding an led).
When I connected the TTL to +5volts (I'm powering the whole thing with 5V)
then I got a current of say 50ma , then without doing any adjustments I connected the TTL to the micro which was outputting a few tens of Khz square wave and the DMM showed more than twice the amount of current , about 120ma.
I understand that the DMM current mode is not designed to measure signal currents so this is an error right? When I give the TTL say.. a 50khz square wave then driver should output half the average current than if I connected the TTL to 5volts right?
Just want to make sure there isn't some trickery going on ...
Thanks in advance for the answers