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From: John Fields on 15 Feb 2010 14:19
On Wed, 03 Feb 2010 13:32:41 -0600, John Fields
<jfields(a)austininstruments.com> wrote:

>On Sun, 31 Jan 2010 20:01:27 -0600, John Fields
><jfields(a)austininstruments.com> wrote:
>
>>On Sat, 30 Jan 2010 17:27:23 -0500, Steve <steve(a)nomail.net> wrote:
>>
>>>On Fri, 29 Jan 2010 17:22:24 -0600, John Fields
>>><jfields(a)austininstruments.com> wrote:
>>>
>>>>On Fri, 29 Jan 2010 17:33:44 -0500, Steve <steve(a)nomail.net> wrote:
>>>>
>>>>>Yes, it does seem that digital would be best for me. This design will
>>>>>also be measuring current during the voltage scan using a computer
>>>>>data acquisition card, so a card with a dac could be used to generate
>>>>>the ramp. But the less expensive 16 bit dac cards do not allow their
>>>>>reference and offset voltages to be set externally, so their range is
>>>>>restricted to +/- 10 V which is 0.3 mV lsb. In practice, that may be
>>>>>ok.
>>>>
>>>>I've already posted a digital scheme which will allow you to accomplish
>>>>what you said you wanted to do, but without the constraints you've
>>>>introduced which the "less expensive" DAC cards will place on you.
>>>>
>>>>can you tell us what, exactly, you want to do and how much money you've
>>>>got to be able to do it with, please?
>>>
>>>This will be scanning voltage for electrochemical compound research
>>>for battery cycling. Slow scan needed because of slow diffusion in
>>>the materials. University research, so money is an issue. Even
>>>hundreds of dollars cost difference can be an issue. Looking for
>>>in-lab built device(s) instead of spending thousands for a commercial
>>>instrument. 12 bit DAC interface cards are $150, 16 bit are $400.
>>
>>---
>>Ahhh! In-lab built!
>>
>>Since you've got in-house test and assembly talent, I'll post a
>>schematic for you in a day or so that should get you what you need for a
>>few hundred dollars, probably including PCB fab if you're careful. ;)
>
>---
>Steve,
>
>"A day or so" has stretched to the beginning of next week, sorry... :(
>
>BTW, how much free I.O. do you have available?

---
Better late than never... ;)

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JF
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