Hi,

Response time for 90% of actual  temperature, i'd like under a minute at
least. I'm fine with doing some simple calculations, but i wouldn't like to
use a lookup table, as if the thermistor would ever need to be replaced, the
table would have to be changed, the measurements taken again, etc. By easy
to program, i mean, a few multiplications/divides/subtracts are okay, but i
don't what any like ln, or sine functions or anything like that.

I'm ok paying up to about $10 roughly for the sensor, but i'm finding the
LM335 and maxim/dallas chips have a very very slow response time, up to
about 3 minutes or more, which isn't what i need. Now thinking about it, an
accuracy or 1 degree is perfectly fine, and with some calibration i  could
probably make it even closer.

I can't use the PICs WDT as i need a small sensor that can fit into small
areas, via a couple of wires.

-Peter
----- Original Message -----
From: "Jinx" <joecolquitt@CLEAR.NET.NZ>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Sunday, December 01, 2002 1:55 PM
Subject: Re: [EE]: Temperature Sensors?


> > What temperature sensors would you recommend for:
> >
> > -Fast Response Time (90% of actual temp)
> > -Relatively Cheap (This is a school project, so nothing that costs
> > $100)
> > -EASY to program for using PIC16F877 - This is a must! Themistors
> > are looking to be very difficult to program for, for a nice accuracy
> > -Accuracy of sub +- 1degreeC
> >
> > I've also messed around with thermistors, just printing out an ADC
> > value and they seem to vary the most, but they are hard to program
> > for as they are non-linear, and they change over age
>
> Use a look-up table to avoid calculations. You'll need to do at least
> one very careful set of measurements to make the table
>
> > Are there any other solutions i haven't thought of? What are your
> > opinions of solution i need?
>
> Use the PIC's WDT. Its period changes with temperature and is
> pretty linear. You can improve the response time of a sensor by
> fixing it to a heatsink - they work both ways. What response time
> are you after ?
>
> "EASY to program" is very subjective. Unless you find a sensor
> that tells you what it knows the way you want it by 8-bit parallel
> data, you'll have to do some calcs
>
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