Poul-Henning Kamp wrote:
> In message <[EMAIL PROTECTED]>, Bruce Griffiths writes:
>
>
>> Offset drift is significantly higher than for other sensors.
>>
>
> On the LTSR they've pinned out the reference, so you can calibrate
> the offset out. I've done it, it's trivial.
>
>
The dc offse
In message <[EMAIL PROTECTED]>, Bruce Griffiths writes:
>Offset drift is significantly higher than for other sensors.
On the LTSR they've pinned out the reference, so you can calibrate
the offset out. I've done it, it's trivial.
>LEM also make dc fluxgate current sensors with 1ppm linearity and
Poul-Henning Kamp wrote:
> In message <[EMAIL PROTECTED]>, Bruce Griffiths writes:
>
>> Poul-Henning Kamp wrote:
>>
>>> If you hook it to a Hall based current-sensor like the LEM LTSR, then
>>> there is no problem with it.
>>>
>>>
>> If a 0.7% accuracy and 6At range suffices.
>>
>
In message <[EMAIL PROTECTED]>, Bruce Griffiths writes:
>Poul-Henning Kamp wrote:
>> If you hook it to a Hall based current-sensor like the LEM LTSR, then
>> there is no problem with it.
>>
>If a 0.7% accuracy and 6At range suffices.
>
>A feedback hall sensor has better linearity, however they h
Poul-Henning Kamp wrote:
> If you hook it to a Hall based current-sensor like the LEM LTSR, then
> there is no problem with it.
>
>
>
If a 0.7% accuracy and 6At range suffices.
A feedback hall sensor has better linearity, however they have a
relatively large offset drift.
If not then an opticall
>>Measuring current gets tricky.
> Actually not, there are several good chips like the INA197.
Mostly, what I was trying to point out is that measuring current probably
won't work well with a simple off-the-shelf general purpose A/D via USB setup.
If you were going to build a gizmo for this sort
In message <[EMAIL PROTECTED]>, Hal Murr
ay writes:
>>>Measuring current gets tricky.
>> Actually not, there are several good chips like the INA197.
>
>Mostly, what I was trying to point out is that measuring current probably
>won't work well with a simple off-the-shelf general purpose A/D via USB
Hi John,
One other possible problem is that the existing shunts may be in the hot side
of the supply. This could exceed the common mode range of the ADC or even the
amplifier (if used).
Robert G8RPI.
John Ackermann N8UR <[EMAIL PROTECTED]> wrote:
Didier Juges wrote:
> Be careful tha
Didier Juges wrote:
> Be careful that if you do not isolate the A/D converter analog circuits from
> the USB ground, you may create all sorts of nasty ground loops with the
> computer. When dealing with power supplies, it's always best to be isolated.
> I do not know enough about USB to know if it
Hal Murray wrote:
> 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.
Sorry... my earlier response blew past the issue of whether you have
enough voltage developed for t
Hal Murray wrote:
>> (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 yo
ement
> 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,
&g
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
> >
In message <[EMAIL PROTECTED]>, Hal Murr
ay writes:
>
>> (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
> (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 cur
Tom Van Baak wrote:
> I like these:
>
> http://www.labjack.com/labjack_u3.php
> http://www.labjack.com/labjack_u12.php
>
> See also:
> http://www.labjack.com/
> http://www.labjack.com/compare.php
Thanks, Tom! Their OEM version of the U3 looks like it'll do the trick,
and at $79 it's not too p
In message <[EMAIL PROTECTED]>, John Ackermann N8UR writes:
>I'm looking for a couple of inexpensive sensors with a couple of
>channels of 10 or 12 bit ADC and ideally a USB interface (emulating a
>serial device).
Consider the ADuC7020 from Analog, Olimex has a board with it:
http://olim
> I'm looking for a couple of inexpensive sensors with a couple of
> channels of 10 or 12 bit ADC and ideally a USB interface (emulating a
> serial device).
John,
I like these:
http://www.labjack.com/labjack_u3.php
http://www.labjack.com/labjack_u12.php
See also:
http://www.labjack.com/
http://
I'm looking for a couple of inexpensive sensors with a couple of
channels of 10 or 12 bit ADC and ideally a USB interface (emulating a
serial device).
I've done a bit of googling and everything I've found has been either
fairly pricey (well over $100 each) or cheap, but with only 8 bits
resolution
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