DS18S20 displays wrong temperatures

[Shozo Kanamori]

My temperature sensor provided by Maxim was actually DS18B20 instead of DS18S20. I found this by carefully observing the sensor's surface with a magnifying glass. I never had doubts about this. The resemblance between "B" and "S" made me spend many hours of frustrating time. Sorry for the viewers.

Shozo Kanamori
It's not easy for hobbyists to get DS18S20 here in Tokyo.

[Lotondo]

Shozo,
here I found a well done prg. for 18B20 that maybe can help you.
http://www.rentron.com/PicBasic/one-wire3.htm

bye

[Shozo Kanamori]

Hi Lotondo,

The article you introduced me seems to be very helpful. I have browsed a lot of webpages but never come across this article before. I will soon start my experiment using DS18B20.

Thank you.

Shozo Kanamori

[Lotondo]

Nice to read that my link maybe helpful.
By the way, I have trouble using ds18S20 with temperature below 0° celsius
if you see some code regarding how to use it, pls link it to me.
Thanks
Bye

[Bruce]

Darell Taylor has some very nice temp conversion routines here http://www.pbpgroup.com/ you might also find very useful.

[Darrel Taylor]

Thanks Bruce!

I was talking with someone else off forum that had problems using the conversion routines with a DS1820 and negative temperatures, so I came up with this.

Sign  VAR  BIT
TempC VAR  WORD

Sign = temperature.15
TempC = ABS(temperature)
TempC =(TempC>>1)*10 + (TempC.0 * 5)
IF Sign then TempC = 0 - TempC

He said it worked, but I haven't tried it myself.

HTH,
  Darrel