[time-nuts] Slightly OT: inexpensive USB analog-digital converter?

Hal Murray hmurray at megapathdsl.net
Fri Jan 18 04:55:14 EST 2008

> (My goal is to add digital voltage and current monitoring to some
> older bench power supplies.) 

Measuring voltage is simple.  If the input range is too big, you need a few 
resistors.  If it's small, you lose a few bits from the top of the A/D.  Add 
an op-amp if you need them.

Measuring current gets tricky.

There are several chips designed for measuring current on 48V busses.  I 
think they are just an instrumentation amplifier with big enough resistors on 
the front end so that the common range goes up to 48V.

Alternatively, if the supply is floating, you can put the sense resistor in 
the ground lead, but you still need a good amplifier to make the signal big 
enough for an ADC.

These are my opinions, not necessarily my employer's.  I hate spam.

More information about the time-nuts mailing list