DS18S20 vs DS2438 for temperature

[NormC]

I've been using both DS18S20's and DS2438's for measuring temperature. The DS18S20's resolution is .06250C and the DS2438 is .03125C. Even though the DS2438 does more than just temerature, seems for accuracy the DS2438 would be better. I have also noticed the DS2438 seems to return a more 'consistent' temperature whereas the DS18S20 seems to jump around more in a 1-2 degree range over a period of a 1-2 minutes.

Has anyone else noticed this? and any disadvantage to using the DS2438 vs the DS18S20 to measure temperature? (besides a littel extra cost).

I'm planning on making something like the Snaku Doc. But mine would be about 20 feet long and measure temperature every foot and use DS2438 devices. This will be submerged in water.

Anyone know of something similar to this already??

Thanks for any advice.

Norm

 

[ericvic]

Norm,

I have not seen the DS18S20 jumping around 1-2 degrees. One thing that the DS18S20 gives you (and I have seen this in my tests) is a more repeatable output across sensors. In my tests two different DS18S20s will give a closer reading to each other and my non 1-Wire temp sensor (don't know how accurate it is) than will two DS2438s. I have seen a spread of about 5 degrees between DS2438s. They all seem to track the changes pretty well through.

The DS2438 does have some advantages though. It converts the temperature faster and is actually cheaper than the DS18S20.

Just my $0.02 worth.

Eric