I have been reluctant in the past to precisely state the requirements as I
believed it would consume too much of peoples time reading, so I tried to
summarise.

Have learnt since that it is efficient to be precise and detailed initially

-----Original Message-----
From: Roman Black [mailto:fastvid@EZY.NET.AU]
Sent: Friday, 28 December 2001 16:59
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [PIC]: current generator with a PIC


ashly Dearden wrote:
>
> I'm thinking of doing some temperature sensing using the approach that
> Dallas and Maxim has with the current source and measuring the voltage
> across a diode-connected transistor.  They don't go into alot of detail on
> what they are doing...other than around 100uA of current. I assume this
must
> be a stable current source and just measure the voltage that is generated?
> I'd like to do this in just a PIC, since its there doing some other stuff
as
> well.  The alternate is to use the MAX1805 and interface the I2C to the
PIC.
> But one chip is better than two...


If you are interested in minimum parts count
a thermistor is cheap and smaller than the
transistor and current source solution. Both
systems will require compensation in software.
Or use Jinx' nifty PIC thermometer which uses
the watchdog timer referenced against the
main clock crystal. How accurate do you need?
I wish people would state EXACTLY what their
needs are when asking for help. :o)
-Roman

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