At 01:43 +1200 27-06-2010, Steve Rooke wrote:
> I don't know if it qualifies as simple/cheap, but Analog Devices and others
have single chip low-rate sigma/delta converters with good to excellent
> properties; these were meant for strain gauges but should be able to track
> slow-moving control voltages just fine. [...]
Do you have any part numbers to hand that I could go and look up
please?
(You didn't specify runtime or resolution; I am assuming that you
plan to monitor an OCXO CV line over several days; this would imply
that you're interested in sub-mV wiggles on a constantish offset of a
few V. Do set me straight if I'm wrong)
I was looking at the Microchip MCP355x-series and Cirrus
CS551x-series. Both are available in DIY-friendly SOIC-packages; if
you can handle SOT-23-6 and TSSOPs your choices widen (ie the AD778x
that Jim Lux mentioned). Both families are S/D converters with
internal digital filtering, offering 20+ bit resolution (although not
all bits are usable, depending on your config).
Most of these parts are available from Farnell and Digi-Key (and if
it were me, I'd order from the latter).
At 10:20 -0500 26-06-2010, Didier Juges wrote:
You may want to check the "Analog Devices MiniKit for ADuC702x-series".
http://www.google.com/search?q=Analog+Devices+MiniKit+for+ADuC702x-series
This kit includes a 24 bit ADC and integrated ARM processor in a
small PWB with all the tools and sample code to do what you want
with very little code to write (you can probably use the sample code
as-is).
Seconded, but note that according to the datasheet it only offers an
internal 12-bit ADC (although the docs from AD seem to contradict
eachother here). This may be Good Enough. The advantage of the
ADuC7xxx series over most other microcontrollers with built-in ADCs
is that the ADuC7xxx ADC has a differential input mode. For more
cheap boards, have a look at Olimex (http://www.olimex.com/dev/).
At 06:21 -0700 26-06-2010, WB6BNQ wrote:
I think using a voltage-to-frequency converter would solve that problem. They
are not too expensive and there are several flavors from Amalog
devices and some others.
Good idea, but might be hard to keep stable enough if my "sub-mV over
days"-assumption is right.
JDB.
--
Years from now, if you are doing something quick and dirty,
you imagine that I am looking over your shoulder and say to
yourself, "Dijkstra would not like this," well that would be
immortality for me. -- Edsger Dijkstra, 1930 - 2002
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