[Diy_efi] Question relating to old posts.....cheapdatalogger?

[Perry Harrington]

Most, even cheap, A/D converters have at least a 10k input impedance.
This is sufficient for reading a thermistor without issue.

--Perry

> I think the real question here should be "What is the input impedance of
> the Dataq board?"  As I understand it the confusion in this thread is
> centered around the note from Dataq stating "this can't be used for
> strain gauges, thermocouples, thermistors, etc."  Obviously, if you've
> ever worked with strain gauges and the like, you know that they're very
> low level signals and often require a differential instrumentation
> amplifier with very good CMRR.  However, in the case of the thermistor
> with the pullup to 5V, the voltage being read is certainly not small,
> but the question of the internal impedance loading the voltage divider
> could affect accuracy.  Worst case, insert an op amp follower (or
> possibly just a common collector/emitter follower transistor buffer.)
> 
> Brian
> 
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-- 
Perry Harrington			Data Acquisition & Instrumentation, Inc	
perry at dainst dot com					 http://www.dainst.com/

Those who would give up essential liberty to purchase a little temporary safety
deserve neither liberty or safety. Nor, are they likely to end up with either.
                             -- Benjamin Franklin

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