[time-nuts] Slightly OT: inexpensive USB analog-digital converter?
didier at cox.net
Fri Jan 18 06:36:24 EST 2008
I forgot the link:
> -----Original Message-----
> From: time-nuts-bounces at febo.com
> [mailto:time-nuts-bounces at febo.com] On Behalf Of Hal Murray
> Sent: Friday, January 18, 2008 3:55 AM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Slightly OT: inexpensive USB
> analog-digital converter?
> > (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.
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