The same solution for scaling I've used at http://geocities.com/vsurducan/c520.htm But is not the simplest way for interfacing... Vasile On Wed, 7 Feb 2001, info wrote: > We achieved what you want but needed a dual op-amp! > We used a dual op-amp and used one side to offset the reference of the > sensor to 0 volts and then used the other side of the op-amp to apply > enough gain to get 100 degrees at 4 volts. This gives me a 40 mV per > degree input to the ADC. This range means a simple right shift of the > ADRESH and you have the temp in centigrade in the register. We wanted to > simplify it further by replacing the op-amp, any ideas? > Scott > > > > In message , > Vasile Surducan writes > >Thys, can you tell me how do you scale the output signal of LM35 to obtain > >full AD pic resolution and how do you convert for displaing celcius > >degrees. AT 0C LM35 output is about 2.7315V and depends of biasing > >current. At 100C will be about 3.73V For a 0..5V AD input, probably you > >need a diferential amplifier or for a pic16F877 to set -ref at 2.73 and > >+ref at 3.73 but in this case you will not have 10 bit AD resolution. > >Is there any more simple method to do that without external amplifiers > >and of course without any one wire or i2c temperature measurement devices. > >Thank's very much, > >Vasile > > > > > >On Wed, 7 Feb 2001, Thys Van Tonder wrote: > > > >> Hi there Peter > >> > >> The LM335 gives you 10mV/0K. So you better use shielded cable. I used the > >> LM35 with about 4m > >> of cable and it worked fine for our application, a bit of switching noise > >> from the motors we were probing. You can average out your reading in the > >> software. > >> > >> Regards > >> Thys > >> > >> -----Original Message----- > >> From: pic microcontroller discussion list > >> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Peter May > >> Sent: 07 February 2001 08:13 > >> To: PICLIST@MITVMA.MIT.EDU > >> Subject: [PIC]: LM335 > >> Importance: Low > >> > >> > >> I gave up on the DS18S20's and went to a simple LM335. It says in the data > >> sheet I can run a long cable to it and use it remotely. In the finished > >> product it will be within a couple of inches of the PIC but for bench > >> testing I want about 20 feet of cable. Would this introduce much noise into > >> the analogue input? > >> > >> -- > >> http://www.piclist.com hint: The list server can filter out subtopics > >> (like ads or off topics) for you. See http://www.piclist.com/#topics > >> > >> -- > >> http://www.piclist.com hint: The list server can filter out subtopics > >> (like ads or off topics) for you. See http://www.piclist.com/#topics > >> > >> > > > >-- > >http://www.piclist.com hint: The list server can filter out subtopics > >(like ads or off topics) for you. See http://www.piclist.com/#topics > > > > > > ******************************************************* > Broadcast Warehouse ( FM Transmitters and accessories ) > website: www.broadcastwarehouse.com > email: info@broadcastwarehouse.com > > phone: > sales: > inland (uk) 0208 5409992 > international +44 208 5409992 > tech support: > inland (uk) 0208 5409993 > international +44 208 5409993 > fax inland (uk) 0208 5409994 > international +44 208 5409994 > ******************************************************* > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics > > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.